Advances of Perovskite Solar Cells

To address the challenge posed by the growing global energy demand, perovskite solar cells (PSCs) present a sustainable and clean solution with the advantage of low cost, high power conversion efficiency (PCE) and easy processing features. As the process of industrialization progresses, it is imperative for PSC to prioritize the resolution of some issues, such as working stability, performance optimization and device structure design. This Special Issue on “Advances of Perovskite Solar Cells” deals with the effect of the intrinsic properties of perovskite films and device structure on the performance of PSCs, as well as their potential for future applications in different fields.

The intrinsic properties of perovskite film are the core of photovoltaic devices. Wang et al. [1] summarized the annealing engineering for the growth of perovskite grains. They divided the main annealing methods into physical and chemical annealing and discussed their impact on the crystal growth mechanisms and device performance. Gan et al. [2] investigated the influence of formamidine formate (FAHCOO) doping on the performance and stability of FAPbI₃-PSCs based on a two-step method. The results show that adding FAHCOO to the PbI₂ precursor solution could passivate iodide vacancy defects in the FAPbI3 films. FAHCOO introduces an ion exchange process that delays the crystallization and induces the growth of (111) planes of FAPbI₃, which could improve the surface morphology and crystallinity of the films as well as the performance of PSCs. SnTiO₃ is a potential Pb-free ferroelectric material with a high dielectric constant and ferroelectric polarization in theory [3]. Behera et al. investigated the prospective applications of SnTiO₃ in optoelectronics and energy storage devices by first-principles calculation from the perspectives of structure, elasticity, electronics, thermodynamics, optics, and thermoelectricity. Additionally, advancements have been made in the investigation of novel photovoltaic materials. Zhou et al. simulated the photonic crystal structure and defect structure of SiC as a light absorption layer [4]. The photonic bandgap and slow light effect of SiC result in an increased light propagation path and a reduced carrier recombination probability, thereby enhancing the absorption efficiency of the light absorption layer.

Several contributions examined the impact of device structure on photovoltaic performance. Alanazi et al. simulated solar cells based on the lead-free double perovskite Cs₂AgBiBr₆ [5]. A double electronic transport layer (ETL) structure was designed to make a band alignment on the SnO₂/absorber interface, which effectively improved the carrier transport efficiency. The optimized device exhibited superior suitability for indoor photovoltaic and low light power generation. Salah et al. examined the translation layer effects of tandem solar cells through simulations [6]. They discovered that using the ETL-free n-p PSC as a top cell could replace the traditional n-i-p structure with higher efficiency and stability, as it reduces the number of layers and interfaces. Additionally, the additives, film thickness, defect density, and energy gap of the functional layers were also investigated to enhance the performance of PSCs.

Some contributions facilitate a broader understanding of perovskite in the field of photoelectric devices. Li et al. [7] reviewed the research progress in perovskite X-ray detectors based on the bibliometric method. Using the CiteSpace tool, they analyzed the literature from 1997 to the present, and discussed some popular materials, preparation methods, research hotspots, and future developments of perovskite X-ray detectors. Deng et al. [8] synthesized phase-pure Rb₂AgI₃ nanocrystals (NCs) using a hot injection method. They analyzed the optoelectronic properties of Rb₂AgI₃ NCs and point out that the wide-gap Rb₂AgI₃ NCs with pure ultraviolet luminescence and high stability have potential applications in optoelectronic nanodevices such as flexible light-emitting diodes or photodetectors operating in the near-UV spectral region. Gu et al. [9] synthesized orthorhombic Cs₂CuCl₄ NCs which exhibit excellent blue emission properties. Compared with the toxic Pb-based perovskites, the Cu-based perovskite NCs show potential application for display and LED lighting. Xu et al. [10] reported a novel thermoresponsive luminescent solar concentrators (LSCs). The researchers demonstrated a smart window (SW) comprising carbon quantum dots (CQDs) introduced into a laminated LSC filled with an aqueous thermosensitive polymer (PNIPAm) solution. As the ambient temperature increases, the LSC-SWs undergo a transition from transparent to opaque states, while maintaining a high power generation capacity.

The present Special Issue on “Perovskite Solar Cells” may be regarded as a status report, providing a summary of the progress achieved over the last five years in perovskite and photoelectric devices.