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Article

Bibliometric Analysis of Research Trends on Quantum-Dot-Sensitized Solar Cells over Two Decades

by
Ho Kim Dan
1,2,
Ha Thanh Tung
3,*,
Duong Van Khanh
4 and
Ho Nguyen
5
1
Optical Materials Research Group, Science and Technology Advanced Institute, Van Lang University, Ho Chi Minh City 70000, Vietnam
2
Faculty of Applied Technology, School of Technology, Van Lang University, Ho Chi Minh City 70000, Vietnam
3
Faculty of Basic Sciences, Vinh Long University of Technology Education, Vinh Long City 7310101, Vietnam
4
Department of Social Work, Dong Thap University, Cao Lanh City 870000, Vietnam
5
Department of Land Management, Dong Thap University, Cao Lanh City 870000, Vietnam
*
Author to whom correspondence should be addressed.
Energies 2023, 16(15), 5734; https://doi.org/10.3390/en16155734
Submission received: 10 June 2023 / Revised: 10 July 2023 / Accepted: 12 July 2023 / Published: 1 August 2023
(This article belongs to the Section A2: Solar Energy and Photovoltaic Systems)
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Versions Notes

Abstract

:
Many years after the introduction of quantum-dot-sensitized solar cells (QDSSCs), publications related to it have been widely disseminated in scientific archives. In this study, a bibliometric analysis was conducted to examine the bibliographic content of publications indexed in the Science Citation Index Expanded database from 2000 to 2021. Over the past two decades, 1557 articles have been published in the field of QDSSCs, covering studies on the photoanode, cathode, and electrolytes of the system. The most active journal, Electrochimica Acta, has published 6.48% of the total number of publications. The three most productive nations are China, South Korea, and India, accounting for 47.4%, 13%, and 9%, respectively, of publications from the top 20 nations. Through keyword analysis, our findings suggest that scholars have focused on controlling the optical and electrochemical properties of active materials, studying power conversion mechanisms, and investigating other internal kinetic mechanisms of QDSSCs. The authors and institutions are also classified based on their scientific performance over the past two decades to determine the intellectual base. This study assesses the general progression in QDSSC research and may provide baseline information to help scholars identify research trends in the field of QDSSCs.

1. Introduction

Humans are addressing global warming, which is projected to cause an average temperature increase of around 1.5 °C in the 21st century [1]. To mitigate the underlying causes of climate change, significant reductions in greenhouse gas emissions, particularly carbon dioxide, are needed on a global scale. One potential solution is the utilization of renewable energy sources such as wind, water, bioenergy, geothermal, and solar energy. Among these, solar energy is abundant and sustainable, providing a total annual energy amount of 3 × 1024 joules. Consequently, a conversion of just 1% of that energy would be sufficient to meet the entire global energy demand [2]. In other words, solar cell efficiency needs to be approximately 10% to address the world’s energy problem [2].
In recent decades, solar cells have witnessed significant advancements. To provide a broad overview of the different generations, highlighting the inclusion of QDSSCs within the context of emerging solar cell technologies, we categorized solar cells into three distinct categories. First-generation solar cells are based on mono- and poly-crystalline Si semiconductors, achieving power conversion efficiencies of 26.7% [3] and 21.9% [4], respectively. Second-generation solar cells consist of thin-film CdTe [5] or amorphous Si [3], which are more cost effective than those of the first generation and exhibit a power conversion efficiency of 21.7% [5]. The third generation includes dye-sensitized solar cells (DSSCs), quantum-dot-sensitized solar cells (QDSSCs), and perovskite solar cells. QDSSCs have attracted significant attention and have undergone rapid development due to their low fabrication cost and the ability to surpass the Schockley–Queisser thermodynamic limit, beyond which photons with lower energy than the material bandgap cannot be absorbed, and those with higher energy waste the energy difference (Ephoton − Egap) as heat. In the third generation of solar cells, this limitation can be overcome by leveraging multiple photon generation effects, the development of p-n junctions, and the use of quantum dots (QDs) instead of dye-sensitized molecules. Theoretically, their power conversion efficiency is predicted to exceed 40% [6].
Recently, numerous articles have been published in the field of QDSSCs, driven by intense competition in science and technology and the demand for green and environmentally friendly energy sources. Consequently, it is crucial for scientists, institutions, universities, and countries to define science policies by analyzing scientific advancements and addressing the need for global innovation. This involves identifying key research areas in the field of QDSSCs and developing an outlook for the future market, policies, and semiconductor industries. Over the years, several studies have been performed examining the history of scientific and technological research in the field of QDSSCs. Garg and colleagues studied solar-cell-related articles in the Engineering Index from 1970 to 1984 and observed a significant increase in scientific publications from 1973 to 1982, following the energy crisis. Garg and Sharma (1991) [7] and Du et al. (2014) [8] used bibliometrics to evaluate literature from the Science Citation Index and Social Science Citation Index databases, respectively, in the field of solar cells from 1992 to 2011. Their findings demonstrated an exponential growth in publications during that period. Qadir et al. (2019) [9] conducted an important study using bibliometrics to analyze and map studies on dye-sensitized solar cells, providing an overview of global research from 2007 to 2017. While bibliometric studies have been successfully applied to examine the progress in various fields, such as Sentinel-1 satellite applications [10], thermal energy storage technology [11], solar cooling technology [12], remote sensing [13], the linkage between renewable energies and sustainable development [14], and solar energy forecasting [15], there is still a lack of studies assessing the evolution of QDSSC publications through bibliometric analysis.
Improving the performance of QDSSCs has always been a prominent topic for scientists. They have focused on enhancing materials used in electrodes, such as counter electrodes, photoanodes, and electrolyte systems. Furthermore, various fabrication methods have been employed to achieve performance improvements. Surface treatment between contact layers to mitigate recombination processes is also a critical consideration. To provide a comprehensive overview of QDSSC research from its inception to the present, this study utilizes bibliometric analysis based on data obtained from the Web of Science. Information on publications in the field of QDSSCs was collected from the Web of Science (WoS) database, and bibliometrics is employed as the primary scientific methodology. The study analyzes the current global situation and trends in QDSSC research by reviewing scientific articles published between 2000 and 2021. It emphasizes the development of QDSSC publications, publishing statistics, and the geographic distribution of authors and institutions that have significantly contributed to the field of QDSSC research.

2. Materials and Methods

2.1. Formulating Research Questions

As previously mentioned, the primary aim of this research is to conduct a bibliometric analysis of all papers related to QDSSC research derived from the Science Citation Index Expanded (SCI-E), an online academic citation index database provided by Web of ScienceTM, ClarivateTM. To accomplish this, we have formulated the following key research questions:
(1)
What is the publication output in the field of QDSSCs?
Answering research question (1) will provide an overview of the annual evolution of QDSSC research over the past two decades, offering insights into potential patterns for the future.
(2)
What is the publishing performance of scholars in QDSSC research based on the quantity of published works and citations?
Answering this question will allow us to assess the amount of work contributed to the field of QDSSCs by scholars.
(3)
What is the geographical distribution and publishing performance of countries in QDSSC research, considering the quantity of publications?
Answering research question (3) will enable scholars to identify which countries are actively involved in the field of QDSSCs, providing information on potential collaborators for future research projects.
(4)
What are the trending topics in QDSSC research over the years?
Answering this research question will help researchers identify the research directions that have been emphasized in the field of QDSSCs. It may also assist scholars in determining their future research directions.

2.2. Data Selection

We selected the WoS Core Collection database (https://www.webofscience.com), specifically the Science Citation Index Expanded (SCI-E), as it is widely recognized and influential in the scientific literature [16]. To gather relevant papers on quantum-dot-sensitized solar cells, we extracted articles from the SCI-E database using three inclusive keywords: “quantum dot sensitized solar cell*”, “QDSSCs”, and “QDSSC”, considering the exploratory nature of our research [17,18,19]. The search was conducted on 31 December 2021. The search covered the time span from 1 January 1990 to 31 December 2021.
We excluded articles categorized as document types other than “Article” and “Review”, as these types typically contain significant research findings in the field of QDSSCs. Our focus was on English-language research articles published between 2000 and 2021 in international peer-reviewed journals. Ultimately, a corpus of 1557 publications was exported in BIB and CSV format files for post-processing and analysis.
To perform bibliometric analysis, we utilized two widely employed and efficient tools: the R package Bibliometrix (version 4.0) [20] and the open-source tool VOSviewer (version 1.6.18) [21]. Bibliometrix facilitated the extraction of various bibliometric indicators, including the annual publication count, citations per paper, h-index of authors and countries, most-cited papers and authors, and the most productive institutions. Furthermore, we employed Bibliometrix to construct keyword co-occurrence networks, aiding in the identification of relevant and frequently used keywords within the QDSSCs literature. VOSviewer was employed to visualize the co-authorship networks among countries.

3. Results and Discussion

3.1. Publication Output

3.1.1. The Growth Trend of Publications in QDSSCs

The collection analyzed in this study comprises a total of 1557 published articles between 2000 and 2021. These articles consist of 1496 research articles (96.1%) and 61 review papers (3.9%) (Table 1).
The publications in the field of QDSSCs between 2000 and 2021 are summarized in Figure 1. The number of publications remained relatively low from 2000 to 2006, with only a few articles being published. However, starting from 2007, with three publications (0.19% of the total), there was a significant increase in the number of QDSSC publications. The highest number of articles, 198 in total (12.72% of the total), was published in 2014, indicating a peak in research activity during that year. The growing demand for green and sustainable energy sources is believed to be the driving force behind this rapid development in the field. Additionally, there has been a significant increase in the conversion efficiency of QDSSCs, reportedly going from less than 1% to more than 15% [22,23], which positions QDSSCs as a promising sustainable energy source. However, after 2015, the progress of this technology slowed down due to challenges in achieving higher efficiency, which hindered its effective deployment in the market. Apart from efficiency concerns, another significant obstacle to the widespread application and commercialization of QDSSCs is their limited performance stability [23].
Furthermore, in 2014, the emergence of lithium and organic solar cells gained attention from scientists, diverting some research focus away from QDSSCs. As a result, there has been a decline in the number of QDSSC publications observed since 2014–2015. In 2021, only 81 articles (5.2% of the total) were published, indicating a decrease in research emphasis on QDSSCs.
On the other hand, the number of citations sharply increased, reaching 30,758 citations in 2015, primarily due to the large volume of previously published articles. The average citation per year reached its highest point of 32 in 2007, surpassing other years, likely due to a particular study that garnered significant attention in the QDSSCs field (Figure 2).

3.1.2. Journal Sources

Of the 1557 total articles in the corpus, 758 articles (48.7%) were published in the top 20 journals in the field of QDSSCs. Table 2 presents these 20 journals, arranged in descending order based on the total number of publications from 2004 to 2021. All of these journals have a high impact factor, indicating their quality and prestige in the field. This reflects the urgency and potential success of research in QDSSCs. With the exception of the Journal of Materials Science in Electronics (Q2) and the Journal of Nanoscience and Nanotechnology (Q3), each of the top 20 journals is ranked in the first quartile of their respective categories. Moreover, except for the Journal of Materials Science: Materials in Electronics, which has an H-index of 75, all other journals in the top 20 have an H-index higher than 100 (Table 2). The journal with the highest number of articles is Electrochimica Acta, with 98 articles, accounting for 6.3% of all publications. It is followed by the Journal of Materials Chemistry A and the Journal of Physical Chemistry C, both with 65 articles, accounting for 4.17% of the total publications.
Figure 3 displays the year-by-year growth of the top 10 publication sources for QDSSCs from 2000 to 2021. The sources “Electrochimica Acta” and “Journal of Physical Chemistry C” show consistent growth throughout the study period. The journal “Solar Energy” was the fastest-growing source in the last five years. On the other hand, two sources, “Physical Chemistry—Chemical Physics” and “ACS Applied Materials & Interfaces”, exhibited a stagnation in growth in recent years.

3.2. The Publishing Performance of Authors

Figure 4 presents the top 20 authors to have made significant contributions to QDSSC research, based on their total number of publications in the field. These authors’ total publications, H-index, citations, and average citations per article are provided. The group of these 20 authors has collectively published 777 articles, accounting for 50% of the total QDSSC-related publications from 2000 to 2021. Kim H.J. has the highest number of publications, with 73 articles, followed by Zhong X. with 60 publications and Li W. with 44 publications. It is important to note that the total number of publications is an academic indicator of an author’s output, but the total number of citations or average citations per article better reflects their scientific contribution to the field. Recently, the scientific community and journals have emphasized the use of the H-index, which takes into account both total citations and publications, as a significant factor in assessing a researcher’s contribution.
Figure 5 showcases the long-term involvement of authors in the field of QDSSCs, including Li Y. (12 years), Shen Q. (12 years), Chen J. (11 years), Li W. (11 years), Lin Y. (11 years), Zhong X. (10 years), Pan Z. (10 years), and Zhang X. (10 years). Their persistence in this research field indicates their belief in its potential, and their anticipation that improving QDSSCs’ power conversion efficiency will lead to more publications. In Figure 6, the size of the data points indicates the number of citations each author received each year.
Table 3 presents the top 15 most-cited articles in the field of QDSSCs. The number of citations is significant, as it correlates with the H-index and represents the contribution of these papers to the QDSSCs field. While citation count alone may not be a perfect indicator of a paper’s significance or impact, it does indicate its recognition by the scientific community [24]. Additionally, the most widely cited papers can provide insights into the development of specific scientific areas [25]. Among these influential papers, Im J.H.’s (2011) [26] and Kamat P.V.’s (2008) [27] papers have received the highest number of citations, with 2304 and 2184 citations, respectively. In 2008, Kamat et al. [27] published their review paper, which focused on quantum-dot-sensitized solar cells, in The Journal of Physical Chemistry C. They presented their findings on electron transport processes, electrode surface treatment, and challenges in the future development of QDSSCs. In 2011, Im J.H. et al. [26] published significant results in the Nanoscale journal, demonstrating the successful improvement of QDSSC performance with an efficiency of 6.5%, which was the highest at that time. The remaining articles in the corpus have received fewer than 1000 citations.

3.3. Geographical Distribution and Publishing Performance of Countries

3.3.1. Countries That Published the Most Articles

As the demand for sustainable energy solutions continues to grow, many countries are investing heavily in research and development in this field. Figure 6 shows the frequency of occurrence of some countries based on their total publications from 2004 to 2021. In general, China has the highest frequency of occurrence, with approximately 2416 appearances, accounting for 47.4% occurrences of the top 20 countries in this field. Several factors have contributed to China’s leading position in the publication of research in the field of QDSSCs. These factors include: (i) Research investment: China has made substantial investments in research and development, particularly in emerging technologies and renewable energy [41,42]. The government has prioritized the development of clean energy solutions, including solar cells, to address environmental concerns and high energy demands; (ii) Policy support: The Chinese government has implemented favorable policies and incentives to promote research and innovation in the renewable energy sector [42]. This support includes funding programs, grants, and tax incentives, which have encouraged researchers and institutions to focus on QDSSCs and related technologies; (iii) Collaboration and networks: Chinese researchers have actively engaged in international collaborations and networks (see Figure 9). They have established partnerships with renowned research institutions and scholars from around the world, facilitating knowledge exchange and collaborative research in the field of QDSSCs. The two countries ranked next after China are South Korea (660 papers; 13%) and India (460 papers; 9%). The USA, Japan, Iran, Spain, and Vietnam each have more than 100 appearances, while the remaining countries have a lower frequency of occurrence. In terms of continents, Asia dominates, accounting for 85% of the occurrences of the top 20 countries in the field. Asian countries are promoting the development of the electronics industry, and focusing on scientific research as the fastest way to achieve their objectives. Additionally, seeking sustainable energy sources, energy conservation, and reducing the impact of the greenhouse effect are core issues for these Asian countries. They are in the midst of industrialization, and electricity is being used to advance the sector quickly [43].
Figure 7 illustrates the total citations of publications between 2004 and 2021 in various countries. China has the highest number of citations, with 25,299, among the top 20 countries in the field of QDSSC research. This corresponds to the large number of publications from China during the same period. The USA, South Korea, Spain, India, and Japan follow, with slightly fewer citations, while Israel has the lowest number of citations among the top 20 countries. However, the average citation per article truly reflects the quality of a country’s publications. Spain, despite having only 4304 citations and ranking fourth among the top 20 countries, has the highest average citation per publication of 165.54. This indicates that Spain’s publications have more influence within the international scientific community, even though they have fewer publications compared to China. Similarly, the USA and Israel have average citations per article of 139.67 and 150.86, respectively, which are higher than those of the remaining countries. This pattern can also be observed in the cases of Singapore and Iran, where Singapore has 570 publications and an average citation of 57, whereas Iran has 869 publications but a much lower average citation of 11.43.

3.3.2. The Most Productive Institutions Publishing Papers Related to QDSSCs

Figure 8 illustrates the affiliations with the highest numbers of publications in the field of QDSSCs from 2004 to 2021. These institutions are predominantly located in the most productive countries, as shown in Figure 7. China leads the research field, with seven affiliations on the list, followed by South Korea with three institutions and the USA with two institutions. QDSSC research in China has experienced rapid growth, supported by national science and technology policies and collaborations with other developed countries [41,42]. Additionally, many students from China pursue studies and research in scientifically advanced nations such as the USA and Japan. Among the top fifteen most productive affiliations, it is noteworthy that 80% (twelve institutions) are from East Asia, including seven from China, three from South Korea, and one each from Taiwan, Japan, and Vietnam. In contrast, it is interesting to observe that there are no institutions from Europe among the top fifteen productive affiliations.

3.3.3. Collaboration Network by Country

Similar to many other scientific and technological fields, countries worldwide have formed deep and extensive networks of cooperation in research related to QDSSCs. Figure 9 demonstrates the growth in research collaboration and publications in the field of QDSSCs among countries. The size of countries and regions indicates the number of partnerships they have; the wider the square, the more partners they have for cooperation. The boldness of the links between countries represents the strength of their collaboration. China serves as the central hub of the research network, with connections to most other countries, including Canada, Sweden, Australia, Saudi Arabia, Pakistan, England, and Singapore. China, South Korea, Japan, India, and the United States exhibit the highest numbers of partnerships with other countries. This demonstrates that research on QDSSCs as an alternative energy source is not limited to European developed countries, but also involves Asian nations, highlighting its global significance.
Energies 16 05734 g009
Figure 9. Collaboration network by country. The thickness of the connecting lines indicates the strength of collaboration between countries, with thicker lines indicating stronger collaboration. The colors used in the graph represent different collaboration clusters, with each color representing a distinct cluster.
Figure 9. Collaboration network by country. The thickness of the connecting lines indicates the strength of collaboration between countries, with thicker lines indicating stronger collaboration. The colors used in the graph represent different collaboration clusters, with each color representing a distinct cluster.
Energies 16 05734 g009

3.4. Research Trends Based on Word Cloud Analysis

Word cloud analysis provides insight into the specific topics and areas of research prioritized in the field of QDSSCs during the studied period. Figure 10 depicts the results of word cloud analysis on titles, abstracts, author’s keywords, and keywords plus, which appeared in all studied articles. Their frequency strongly depends on the research topic. The keyword “solar cell” or “solar cells” includes several specific keywords about the composition and electro-optical properties of materials or fabrication methods, such as “quantum dot”, “TiO2”, “photoanode”, “counter electrode”, “CdSe”, “successive ionic layer adsorption and reaction”, “CuS”, “electron combination”, “energy conversion”, “recombination” or “electrochemistry”. Meanwhile, the keyword “stability” rarely appears, and is mostly related to research on the stability of QDSSCs. This shows that from 2004 to 2021, scientists focused their research on controlling the optical and electrochemical properties of active materials, studying power conversion mechanisms and other internal kinetic mechanisms of QDSSCs, e.g., the movement of electrons generated from quantum dots and transferred to an external circuit, and focusing on improving QDSSCs power conversion efficiency. The frequent appearance of keywords related to the composition and electro-optical properties of materials and fabrication methods indicates that researchers were focused on improving the efficiency of QDSSCs by controlling these properties. In another respect, “electrolyte” is a keyword in the QDSSC research field, but can be found in only a few instances in the data cloud analysis, indicating that it has the least importance in the field.
Figure 11 visualizes the extracted author’s keywords by grouping them into several categories using clustering methods and MDS. According to the conceptual structure map of the top 50 author’s keywords, three primary clusters can be identified in the published works in the field of QDSSCs from 2000 to 2021, indicated by the colors red, green, and blue. The red cluster, considered the most comprehensive, includes 44 of the top author’s keywords, such as quantum dot, graphene, photovoltaics, TiO2, ZnO, QDSCs, quantum-dot-sensitized solar cells, electrocatalytic activity, nanostructures, impedance spectroscopy, and others. These keywords are commonly used by scholars to accurately represent the content of the articles, as they directly relate to the content of QDSSCs, efficiency, performance, and dynamic processes in solar cells. The blue cluster consists of four author’s keywords, including titanium dioxide, cadmium sulfide, cadmium selenide, and sensitized solar cells. Most publications containing these keywords aim to expand the study topics in QDSSCs, such as surface treatment and efficiency improvement. The green cluster encompasses the remaining two author’s keywords from the top 50, namely electrode and counter. The research articles in this cluster suggest using counter electrodes to study and enhance performance.
In general, based on the obtained data, we identified two proposed trends that scientists could consider as guides for further research in QDSSCs. Firstly, QDSSCs experience significant electron loss during excitation. There are various types of loss that can occur while QDSSCs are operating, including recombination within QDs or on their surface as a result of imperfect fabrication, electron loss during transport across the QD/semiconductor oxide interface, electron diffusion inside the semiconductor oxide film, QD corrosion by the electrolyte, and electron loss due to redox reaction at the electrolyte/antielectrode interface. The loss of QDs caused by internal and surface flaws is either restricted to those made using high-temperature colloidal processes or extended to those made using the different techniques. Secondly, for new materials such as: Since the material is a mixture of two or more materials with differing bandgap energies, this problem is avoided for materials with intermediate band structure. In accordance with the energy gaps between the valence and conduction bands of the material with the shorter bandgap and the two conduction bands of the two materials, photons with various energies are absorbed. As a result of these absorptions, the excited electron concentration in the larger bandgap material’s conduction band is increased. These excited electrons are then gathered and transmitted to an external circuit, where they produce electric current density. Due to the anticipated power conversion efficiency (PCE) in QDSSCs of up to 46% [44], these intermediate band structure materials have a high potential to replace conventional photosensitive materials.

3.5. Potential Implications

Overall, this study can provide valuable insights into the current state of QDSSC research and can help to guide future research directions and collaborations within the field. By analyzing the publishing statistics and geographic distribution of authors and institutions, the study can help identify the leading contributors to QDSSC research. This information can be used to guide collaborations and partnerships, as well as to inform funding decisions and resource allocation. In addition, by providing a comprehensive overview of the research landscape in QDSSCs, the results of this study can help to advance the field by highlighting areas of research strength and identifying potential opportunities for further research. This information can be used to guide future research directions and to inform the development of new QDSSCs technologies and applications.
Furthermore, this study can help identify potential collaborations and research networks within the field of QDSSCs. The results of this study can be used to facilitate communication and knowledge sharing between researchers, and to promote the development of interdisciplinary research initiatives.

3.6. Limitations

There are some limitations to this study that need to be acknowledged. Firstly, this study primarily focuses on publications in the field of QDSSCs from the WoS Core Collection—SCI-E database, which may result in the omission of relevant publications from reputable peer-reviewed journals that are not indexed in the SCI-E database. Therefore, future work should consider including other databases such as Scopus and Google Scholar. Secondly, it is possible that our search strategy may have missed some relevant publications. Lastly, our analysis only includes articles and review papers, thereby potentially overlooking important studies published in conference proceedings, book chapters, and books.

4. Conclusions

In light of the escalating global warming crisis, there is an urgent need to reduce greenhouse gas emissions through the utilization of renewable energy sources such as solar energy. This study aimed to assess the bibliometric status of research conducted in the field of quantum-dot-sensitized solar cells (QDSSCs). Generally, there has been a significant increase in global publications in the field of QDSSCs from 2000 to 2021, particularly between 2004 and 2015. Notably, in 2014, 13.35% of all publications in the QDSSCs field were recorded. This study also highlights those publications with the highest citation counts, the most major contributions from renowned scientists, and the most prestigious universities and institutions worldwide to have made significant research contributions to the study of QDSSCs. The analysis of international collaboration networks revealed a particularly remarkable cooperative relationship between China, the USA, and European countries. By providing researchers with a comprehensive understanding of the overall landscape of QDSSC research and facilitating the identification of potential collaborators, we believe that this study will be highly beneficial. Furthermore, given the industry’s strong reliance on research endeavors, countries should consider formulating industrial policies to anticipate and support the future growth of the QDSSCs industry.

Author Contributions

Conceptualization, H.N., H.T.T. and H.K.D.; methodology, H.N. and H.T.T.; software, H.N. and D.V.K.; validation, H.N., H.T.T. and H.K.D.; formal analysis, H.N., H.T.T. and D.V.K.; resources, H.N. and H.T.T.; data curation, H.N. and D.V.K.; writing—original draft preparation, H.N., H.T.T. and H.K.D.; writing—review and editing, H.K.D., H.N., H.T.T. and D.V.K.; visualization, H.N. and D.V.K.; supervision, H.T.T. and H.K.D.; project administration, H.T.T. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Not applicable.

Acknowledgments

The author would like to thank Massimo Aria and Corrado Cuccurullo for developing the “Biblioshiny” tool, and Nees Jan van Erik and Ludo Waltman for developing the “VOSviewer” tool, both of which were used for data processing and data visualization in this study. We thank Binh Pham-Duc for his valuable suggestions on earlier drafts of the manuscript. Additionally, we would like to thank Thao Mai-Thi for her assistance with English editing of the manuscript.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Annual scientific production and the trend-line (with three-period moving average) in the collections.
Figure 1. Annual scientific production and the trend-line (with three-period moving average) in the collections.
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Figure 2. Number of annual scientific publications and average article citations in the collections.
Figure 2. Number of annual scientific publications and average article citations in the collections.
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Figure 3. Year-wise growth of the 10 most productive publication sources.
Figure 3. Year-wise growth of the 10 most productive publication sources.
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Figure 4. Top 20 authors based on their total publications in the QDSSC research field.
Figure 4. Top 20 authors based on their total publications in the QDSSC research field.
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Figure 5. Long-term production of top authors in the field.
Figure 5. Long-term production of top authors in the field.
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Figure 6. Scientific production of the top 20 countries.
Figure 6. Scientific production of the top 20 countries.
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Figure 7. Countries with the most publications and their numbers of citations.
Figure 7. Countries with the most publications and their numbers of citations.
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Figure 8. Top 15 institutions based on total number of publications in the collections.
Figure 8. Top 15 institutions based on total number of publications in the collections.
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Figure 10. Visualized word clouds from (a) titles; (b) abstracts; (c) author’s keywords; and (d) keyword plus.
Figure 10. Visualized word clouds from (a) titles; (b) abstracts; (c) author’s keywords; and (d) keyword plus.
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Figure 11. Conceptual structure map (with multidimensional scaling method (MDS)) of the top 50 author’s keywords index in the field of QDSSCs. Black points represent keywords, while the three colors, red, green, and blue, indicate the three primary clusters in the published works in the field of QDSSCs from 2000 to 2021 based on keywords.
Figure 11. Conceptual structure map (with multidimensional scaling method (MDS)) of the top 50 author’s keywords index in the field of QDSSCs. Black points represent keywords, while the three colors, red, green, and blue, indicate the three primary clusters in the published works in the field of QDSSCs from 2000 to 2021 based on keywords.
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Table 1. Main features of articles studied in this work.
Table 1. Main features of articles studied in this work.
CategoryFeatureIndex
GeneralTimespan2000–2021
Total publications1557
Journal Sources234
Average years from publication6.18
Average citations per publication40.16
Average citations per year per publication4.35
Reference1
Publication classificationArticle1496
Review61
Publication contentKeywords Plus (ID)1585
Author’s Keywords (DE)2069
AuthorNumber of authors3040
Author appearances8029
The authors of single-authored publication12
The authors of multi-authored publication3028
Author CollaborationSingle-authored publication19
Publications per author0.512
Author per publication1.95
Co-authors per publication5.16
Table 2. Top 20 active journals and their rankings in the field of QDSSCs.
Table 2. Top 20 active journals and their rankings in the field of QDSSCs.
JournalsArticles% TotalSCImago Quartile *H-Index
Electrochimica acta986.477Q1236
Journal of materials chemistry A654.296Q1212
Journal of physical chemistry C654.296Q1128
RSC advances583.833Q1148
Journal of power sources573.767Q1302
ACS applied materials & interfaces543.57Q1228
Solar energy483.173Q1181
Journal of materials science-materials in electronics402.644Q275
Journal of alloys and compounds362.38Q1172
Physical chemistry chemical physics332.181Q1239
Solar energy materials and solar cells261.718Q1186
Journal of physical chemistry letters231.52Q1203
Journal of nanoscience and nanotechnology221.454Q3105
Nanoscale211.388Q1224
Applied surface science201.322Q1188
Materials letters201.322Q1144
New journal of chemistry191.256Q1122
Applied physics letters181.19Q1442
Nanoscale research letters181.19Q1107
Chemical communications171.124Q1333
* Note that the Scimago Quartile and H-index are updated for 2020 according to the SCImago Journal and Country Rank.
Table 3. Top 15 most-cited articles in the field of QDSSCs.
Table 3. Top 15 most-cited articles in the field of QDSSCs.
PaperTitleJournalTotal CitationsSource
IM JH, 2011,6.5% efficient perovskite quantum-dot-sensitized solar cellNanoscale2304[20]
KAMAT PV, 2008,Quantum Dot Solar Cells Semiconductor Nanocrystals as Light HarvestersThe Journal of Physical Chemistry C2184[27]
LEE YL, 2009,Highly Efficient Quantum-Dot-Sensitized Solar Cell Based on Co-Sensitization of CdS/CdSeAdvanced Functional Materials969[28]
FABREGAT-SANTIAGO F, 2011,Characterization of nanostructured hybrid and organic solar cells by impedance spectroscopyPhysical Chemistry Chemical Physics926[29]
LESCHKIES KS, 2007,Photosensitization of ZnO Nanowires with CdSe Quantum Dots for Photovoltaic DevicesNano Letters868[30]
SANTRA PK, 2012,Mn-Doped Quantum Dot Sensitized Solar Cells: A Strategy to Boost Efficiency over 5%Journal of the American Chemical Society806[31]
RUHLE S, 2010,Quantum-Dot-Sensitized Solar CellsChemPhysChem748[32]
MORA-SERO I, 2009,Recombination in Quantum Dot Sensitized Solar CellsAccounts of Chemical Research702[33]
LEE HJ, 2009,Efficient CdSe Quantum Dot-Sensitized Solar Cells Prepared by an Improved Successive Ionic Layer Adsorption and Reaction ProcessNano Letters593[34]
GONZALEZ-PEDRO V, 2010,Modeling High-Efficiency Quantum Dot Sensitized Solar CellsACS Nano572[35]
BANG JH, 2009,Quantum Dot Sensitized Solar Cells. A Tale of Two Semiconductor Nanocrystals: CdSe and CdTeACS Nano509[36]
TVRDY K, 2011,Photoinduced electron transfer from semiconductor quantum dots to metal oxide nanoparticlesProceedings of the National Academy of Sciences504[37]
ZHANG L, 2015,Anchoring Groups for Dye-Sensitized Solar CellsACS Applied Materials & Interfaces474[38]
PAN Z, 2014,High-Efficiency “Green” Quantum Dot Solar CellsJournal of the American Chemical Society468[39]
FABER MS, 2014,Earth-Abundant Metal Pyrites (FeS2, CoS2, NiS2, and Their Alloys) for Highly Efficient Hydrogen Evolution and Polysulfide Reduction ElectrocatalysisThe Journal of Physical Chemistry C444[40]
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Dan, H.K.; Tung, H.T.; Khanh, D.V.; Nguyen, H. Bibliometric Analysis of Research Trends on Quantum-Dot-Sensitized Solar Cells over Two Decades. Energies 2023, 16, 5734. https://doi.org/10.3390/en16155734

AMA Style

Dan HK, Tung HT, Khanh DV, Nguyen H. Bibliometric Analysis of Research Trends on Quantum-Dot-Sensitized Solar Cells over Two Decades. Energies. 2023; 16(15):5734. https://doi.org/10.3390/en16155734

Chicago/Turabian Style

Dan, Ho Kim, Ha Thanh Tung, Duong Van Khanh, and Ho Nguyen. 2023. "Bibliometric Analysis of Research Trends on Quantum-Dot-Sensitized Solar Cells over Two Decades" Energies 16, no. 15: 5734. https://doi.org/10.3390/en16155734

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