Optical Transitions Dominated by Orbital Interactions in Two-Dimensional Fullerene Networks

Abstract

Fullerenes are a class of highly symmetric spherical carbon materials that have attracted significant attention in optoelectronic applications due to their excellent electron transport properties. However, the isotropy of their spherical structure often leads to disordered inter-sphere stacking in practical applications, limiting in-depth studies of their electron transport behavior. The successful fabrication of long-range ordered two-dimensional fullerene arrays has opened up new opportunities for exploring the structure–activity relationship in spatial charge transport. In this study, theoretical calculations were performed to analyze the effects of different periodic arrangements in two-dimensional fullerene arrays on electronic excitation and optical behavior. The results show that HLOPC₆₀ exhibits a strong absorption peak at 1050 nm, while TLOPC₆₀ displays prominent absorption features at 700 nm and 1300 nm, indicating that their electronic excitation characteristics are significantly influenced by the periodic structure. Additionally, analyses of orbital distribution and the spatial electron density reveal a close relationship between carrier transport and the structural topology. Quantitative studies further indicate that the interlayer interaction energies of the HLOPC₆₀ and TLOPC₆₀ arrangements are −105.65 kJ/mol and −135.25 kJ/mol, respectively. TLOPC₆₀ also exhibits stronger dispersion interactions, leading to enhanced interlayer binding. These findings provide new insights into the structural regulation of fullerene materials and offer theoretical guidance for the design and synthesis of novel organic optoelectronic materials.

1. Introduction

Organic optoelectronic materials, characterized by their optoelectronic activity, play a pivotal role in various applications such as organic light-emitting diodes (OLEDs) [1], dye-sensitized solar cells [2], organic–inorganic perovskite solar cells [3,4,5], and organic transistors [6]. Organic optoelectronic materials are usually organic systems that are rich in carbon atoms and have large π-conjugated electrons. Two-dimensional carbon materials, such as graphene [7,8,9] and graphdiyne [10,11,12], have unique p_z orbital electron transport properties and have attracted much attention due to the special carrier transport properties generated by the unique π-electron system in the conjugated carbon network structure [13]. Among carbon materials, fullerenes stand out as particularly important. They are widely used in new solar cells and other fields due to their high electron affinity, low recombination energy, high electron mobility (5.09 cm²/Vs at 298.15 K), and isotropic transport properties [14,15]. New solar cells, including dye-sensitized solar cells, organic–inorganic hybrid perovskite solar cells, and quantum dot solar cells, are a promising class of photovoltaic devices. In organic solar cells, fullerene materials function as active layer acceptors, receiving and transferring electrons. They can also serve as electron transport layers to enhance compatibility with active layer materials. In perovskite solar cells, fullerene materials can be used as active layer additives to passivate perovskite defects and suppress the hysteresis effect. Additionally, they can be employed as an intermediate layer to optimize the interface morphology and promote charge extraction and transport.

In 1985, scientists such as Curl and Smalley discovered fullerenes [16], whose unique structure and optoelectronic properties have attracted the extensive attention of researchers. In the early 1990s, the discovery of fullerene (C₆₀) crystals and subsequent research revealed the unique physical properties of this material. In particular, C₆₀ crystals doped with alkali metals exhibit extraordinary superconducting properties, greatly stimulating the interest of the scientific community. One of the earliest studies, by Hebard et al., found that potassium-doped C₆₀ exhibits superconductivity at 18 K [17]. This discovery quickly led to a large number of theoretical studies on the structure of C₆₀ crystals and their electronic properties. So far, many new fullerenes have been discovered by scientists, including hollow fullerenes, endohedral metallofullerenes, fullerene derivatives, and nitrogen fullerenes [18,19]. Zheng Jian et al. published a paper in Nature and developed a new interlayer bond cleavage strategy to prepare a two-dimensional monolayer polymerized fullerene semiconductor [20], promoting a large number of scientists to conduct research on it [21,22]. In this monolayer polymer C₆₀, the cluster cages of C₆₀ are covalently bonded to each other in plane, forming a regular topology different from conventional 2D materials. Furthermore, the monolayer polymer C₆₀ exhibits interesting in-plane anisotropy properties and a moderate band gap of 1.6 eV, which makes it a potential candidate for optoelectronic devices such as solar cells and light-emitting diodes.

In the past, related articles [23,24,25,26] have reported research on fullerene excitons in systems such as fullerene films, fullerene polymers, and fullerene derivatives, and have revealed the charge transfer characteristics of fullerenes in different states. Experimental and theoretical studies have shown that C₆₀ molecules can form covalent bonds under high-pressure conditions. Covalently bonded C₆₀ structures have higher stability and more unique electronic properties [27,28]. This stability and these properties give it an advantage in some applications compared to the non-covalently interacting C₆₀ structure. Covalently bonded C₆₀ films may exhibit better tolerance and stability under high-temperature or current density conditions. These studies support our hypothesis regarding the covalent bonding of C₆₀ molecules. This covalently bonded C₆₀ structure provides a unique model system that allows us to delve deeper into the nature and mechanisms of intermolecular interactions. By studying this highly ordered and well-defined covalent bond binding system, we are able to more clearly reveal the microscopic details of the interactions between C₆₀ molecules, which has important fundamental scientific implications for understanding and regulating the properties of materials. So, we employ a novel periodic TDDFT technique to calculate the optoelectronic properties of two-dimensional fullerene arrays with two different packing modes of hexagonal and tetragonal long-range ordered poly-C₆₀ (HLOPC₆₀/TLOPC₆₀). At present, a small number of studies on periodic TDDFT have been reported, and these studies have achieved good results in optics and other fields [29,30,31,32].

In this work, the cross-space charge transport properties between spherical systems of fullerenes are discussed, as these are crucial for understanding the structure–activity relationship between electron transport properties and the structure of π-systems. The studied systems, HLOPC₆₀ and TLOPC₆₀, are neutral in nature, allowing for a clear analysis of their intrinsic charge transport properties without the influence of external charges. We also performed detailed qualitative and quantitative studies on the intralayer interactions of HLOPC₆₀ and TLOPC₆₀. This research aims to offer theoretical guidance for the application of novel organic optoelectronic transport materials.

2. Calculation Method

The crystal structures used in this work were extracted from single-crystal diffraction CIF files (CCDC 2159850, CCDC 2159902, from [20]). Electronic excitation calculations for periodic systems were performed by the first-principles program-CP2K [33] through time-dependent density functional theory (TDDFT) combined with PBE functionals [34] and the DZVP-MOLOPT-SR-GTH pseudopotential basis set. The Tamm–Dancoff approximation (TDA) was employed during the excitation calculation. The studied systems are two-dimensional and neutral, ensuring that the intrinsic electronic properties and excitation characteristics can be explored without interference from external charges or dopants. To account for the periodic nature of the systems, only the two-dimensional plane direction was set to be periodically repeated in the TDDFT calculations. Since CP2K’s TDDFT calculations consider only Gamma points, the lattice vectors in the periodic direction were set to approximately 15 Å to ensure calculation accuracy. The charge transfer modes for different excited states are described by charge differential density (CDD) maps [35,36,37]. These clearly represent the transfer process of electrons and identify regions of electron and hole density. Additionally, seven quantitative transition indices were provided to supplement the CDD analysis. All wave function analyses were based on the wave function files generated by CP2K under the PBE functional and DZVP-MOLOPT-SR-GTH basis set. The wave function analysis used in this article was performed by the multi-function wave function analysis software Multiwfn 3.8 [38]. The methods and formulas used to perform the wave function analysis involved in this work are detailed in the Supplementary Information. All three-dimensional structure diagrams are drawn by VMD [39].

3. Result and Discussion

We investigated the optoelectronic properties of two-dimensional fullerene arrays (Figure 1) with two different packing modes by the first-principles software CP2K, and visualized the electron transfer mechanism by CDD. The purpose of this study was to explore the cross-space charge transport properties between the spherical systems of fullerenes, and to examine the structure–activity relationship between the electron transport properties and structures of π systems. In the CDD diagram, the electron and hole densities are defined as follows:

$${\rho }^{\mathit{hole}}\left(r\right)={{\displaystyle \sum _{i\to a}\left({\omega }_i^a\right)}}^2{\phi }_i{\phi }_i-{{\displaystyle \sum _{i\leftarrow a}\left({{\omega }^{\prime }}_i^a\right)}}^2{\phi }_i{\phi }_i+{\displaystyle \sum _{i\to a}{\displaystyle \sum _{j\ne i\to a}{\omega }_i^a{\omega }_j^a{\phi }_i{\phi }_j-}}{\displaystyle \sum _{i\leftarrow a}{\displaystyle \sum _{j\ne i\leftarrow a}{{\omega }^{\prime }}_i^a{{\omega }^{\prime }}_j^a{\phi }_i{\phi }_j}}$$

(1)

$${\rho }^{\mathit{ele}}\left(r\right)={{\displaystyle \sum _{i\to a}\left({\omega }_i^a\right)}}^2{\phi }_a{\phi }_a-{{\displaystyle \sum _{i\leftarrow a}\left({{\omega }^{\prime }}_i^a\right)}}^2{\phi }_a{\phi }_a+{\displaystyle \sum _{i\to a}{\displaystyle \sum _{i\to b\ne a}{\omega }_i^a{\omega }_i^b{\phi }_a{\phi }_b-}}{\displaystyle \sum _{i\leftarrow a}{\displaystyle \sum _{i\leftarrow b\ne a}{{\omega }^{\prime }}_i^a{{\omega }^{\prime }}_j^b{\phi }_a{\phi }_b}}$$

(2)

where $\omega$ is the excitation configuration coefficient, ${\omega }^{\prime }$ is the de-excitation configuration coefficient, $r$ is the coordinate vector, $\phi$ is the orbital wave function, $i$ or $j$ is the occupied orbital label, and $a$ or $b$ is the empty orbital label. Thus, ${\displaystyle \sum _{i\to a}}$ represents every excitation configuration of the cycle, and ${\displaystyle \sum _{i\leftarrow a}}$ represents every de-excitation configuration of the cycle.

Subsequently, the optical absorption properties of the two-dimensional fullerene system were investigated. Firstly, the optical gap of hexagonal two-dimensional fullerene was calculated to be 1.64 eV. This differs by only 0.09 eV from the experimentally measured value of 1.55 eV, reflecting the reliability of the current computational approach. Figure 2A shows the absorption spectrum of HLOPC₆₀. In the wavelength range of 300–2000 nm, there is a strong absorption peak contributed by a large number of excited states. The excited states that primarily contribute to the absorption peak are S₃, S₁₉, S₇₀, S₈₂ and S₁₄₄. S₃ (Figure 2B) exhibits significant hole density at the double covalent bonds (two covalent bonds between fullerenes) where the fullerene is attached, and a pronounced electron density at the single covalent bond (single covalent bond between fullerenes). This shows that there is charge transfer between the fullerene and the covalent bond at the junction, which will promote the flow of electrons in the two-dimensional plane. Although higher excited states such as S₁₉ and S₇₀ are less relevant for direct charge transport properties, they provide critical insights into charge density distributions and symmetry effects. These factors indirectly influence the electronic structure and overall transport characteristics of the system. Including these states ensures a comprehensive evaluation of both the optical and electronic behaviors under different stacking configurations. The charge transfer behavior of S₁₉ (Figure 2C) is very obvious, with charge transfer occurring on both sides of HLOPC₆₀. A substantial number of electron and hole densities are distributed on either side of the plane, illustrating the transfer of electrons from one side of HLOPC₆₀ to the other. The absence of electron and hole densities at the covalent bond connecting the fullerenes in S₇₀ (Figure 2D) suggests that the charge recombination of S₇₀ occurs inside the fullerenes. The charge transfer patterns within fullerenes for S₈₂ (Figure 2E) and S₁₄₄ (Figure 2F) are very similar. The electron density of the two is mainly distributed on one side of HLOPC₆₀, while the distribution of the hole density is relatively average. The difference between the two is that S₈₂ has a high density of holes at the covalent bonds that hold fullerenes together, while S₁₄₄ does not.

Figure 3A is the absorption spectrum of TLOPC₆₀. There are two strong absorption peaks in the wavelength range of 300–2000 nm, which are jointly contributed by multiple excited states. The absorption peak at 1300 nm is mainly contributed by S₂₉ and S₅₀, and the absorption peak at 700 nm is mainly contributed by S₁₃₄, S₁₅₂ and S₁₇₆. It can be found by observation that the charge transfer patterns of S₂₉ (Figure 3B) and S₅₀ (Figure 3C) are the same. The common point of the two is the obvious electron density at the single covalent bonds, and the hole density on both sides of the TLOPC₆₀ plane is larger. Therefore, S₂₉ and S₅₀ are mainly charge transfer from both sides of the plane to the single covalent bonds. The charge transfer modes of S₁₃₄ (Figure 3D) and S₁₇₆ (Figure 3F) are the same within the fullerene, with the common feature being the higher electron density on both sides of the TLOPC₆₀ plane. The difference between the two is that S₁₃₄ has an obvious hole density at the double covalent bonds, while S₁₇₆ does not. Therefore, S₁₃₄ and S₁₇₆ are mainly charge transfer from the vicinity of the double covalent bonds to both sides of the plane. Finally, S₁₅₂ (Figure 3E) has no electron and hole density at both single and double covalent bonds, so S₁₅₂ is charge recombination within the fullerene monomer. The transition indices (Sr, D, H, t, HDI, EDI, and TDM) provided in

Table 1. Transition indexes of excited states in HLOPC₆₀.

	S3	S19	S70	S82	S144
Sr	1.39	1.26	1.59	1.58	1.61
D (Å)	0.43	1.22	0.26	0.47	0.68
H (Å)	9.83	9.74	9.92	9.98	10.00
t (Å)	−3.57	−1.82	−3.07	−3.98	−2.54
HDI	2.71	2.79	2.62	2.50	2.40
EDI	2.84	2.95	2.62	2.88	2.58
TDM	3.29	4.97	2.69	3.40	2.50

and

Table 2. Transition indexes of excited states in TLOPC₆₀.

	S29	S50	S134	S152	S176
Sr	1.38	1.46	1.17	1.42	1.24
D (Å)	0.03	0.01	0.03	0.01	0.01
H (Å)	9.91	9.99	10.18	10.33	10.20
t (Å)	−5.79	−5.18	−3.01	−5.02	−4.35
HDI	2.27	2.26	3.17	2.58	2.87
EDI	2.81	2.98	2.41	3.4	2.59
TDM	2.56	5.65	2.00	2.78	2.49

quantitatively describe the transition characteristics of each excited state. These indices can be used to evaluate the overlap between holes and electrons, the distance between the centroids of holes and electrons, the average spatial extent of holes and electrons, as well as the degree of separation between them. Such quantitative analysis allows for a deeper understanding of the electronic excitation processes and their relationship with the optical response of the material. The meaning of the transition index can be found in the principles and formulas used in the wave function analysis shown in the Supplementary Information section.

Based on the above analysis, it is evident that the nature of space charge transfer (electron transport) is modulated by orbital interactions in different arrangement modes. At the same time, it was found that there is a distinct structure–effect relationship between the carrier transport and periodic topology.

Next, we study the orbital contribution of the excited states of the two structures during the transition process. This analysis is essential for understanding the nature of the charge transfer in each excited state. Tables S1 and S2, respectively, show the orbital pairs and the percentages that make a major contribution (>10%) to each excited state. In HLOPC₆₀ and TLOPC₆₀, most of the excited states are predominantly governed by a pair of orbital transitions (>50%). Figure 4, Figure 5, Figures S1 and S2 depict the occupied and unoccupied orbitals in HLOPC₆₀ and TLOPC₆₀, which mainly contribute to each excited state. Two key phenomena were observed during the examination of different molecular orbitals. First, different packing modes can significantly affect the orbital distribution of LOPC₆₀. Secondly, it is found that the C-C bonds connecting the two five-membered rings in fullerenes in all occupied orbitals of low-symmetry HLOPC₆₀ have obvious π orbital distributions, but there is no orbital distribution at the charge transfer bonds of empty orbitals. In TLOPC₆₀, neither occupied nor empty orbitals have π orbital distribution at the charge transfer bond. This indicates that asymmetric or distorted organic ring structures with low orbital wave function symmetry have excellent and unique transport properties, and are also excellent electron transport outlets.

AIM (Atoms-In-Molecules) [40,41,42,43] is an extremely well-known and important method developed by Bader to investigate the electronic structure. In this section, we investigate different real-space functions at representative bond critical points (BCPs), ring critical points (RCPs), and cage critical points (CCPs) in HLOPC₆₀ and TLOPC₆₀ (Figure 6A). We define four representative critical points, which are the BCP at the double and single covalent bonds connecting the fullerenes, the RCP at the center of the double covalent bond, and the CCP at the center of the fullerenes (Figure 6B). Two fullerenes can be linked by single and double covalent bonds. In AIM theory, BCPs are considered to be the most representative points in the interaction region between atoms, so the properties of the BCP can be used to investigate the characteristics of corresponding chemical bonds, including their strength and nature. The electron density ($\rho$) and potential energy density ($V$) of BCP are closely related to the strength of chemical bonds; the latter is reflected in the external potential felt by the electrons at the BCPs, and $V$ must be negative. For the same chemical bond, generally the larger $\rho$ (BCP) and the more negative $V$ (BCP), the bigger the chemical bond strength. The single and double covalent bonds are not significantly different for the two structures of HLOPC₆₀ and TLOPC₆₀. However, the electron density of the BCP in TLOPC₆₀ is larger than that of HLOPC₆₀, and the potential energy density of the BCP in TLOPC₆₀ is also more negative. This indicates that the connection of the two fullerenes in TLOPC₆₀ is more stable. It has been reported that when the energy density ($H$) (BCP) < 0, the chemical bond can be considered as covalent, while $H$ > 0 is non-covalent [35]. It can be seen that $H$ at BCP1, BCP2 and RCP is negative. There is no doubt that BCP1 and BCP2 are judged covalently, but why is $H$ at RCP also negative? In Figure 6B, it can be seen that RCP is located in the middle of the double covalent bond, and that $H$ at the RCP will be affected by the covalent bond, thereby reflecting a weak covalent component. The Laplacian of electron density ($\nabla 2\rho$) is defined as the sum of three diagonal elements of the electron density Hessian matrix at the critical point. If $\nabla 2\rho$ < 0 in the bonding region, it can generally be considered that a covalent bond is formed. This is consistent with the results of judging the strength of covalent bonds by $\rho$, $V$ and $H$. The kinetic energy of the BCP is reflected as a large positive value, and the kinetic energy of the BCP in TLOPC₆₀ is larger. The kinetic energy of the RCP is a very small positive value of 0.0027a.u., and its kinetic energy is negligible. The electron localization function (ELF) is a quantum chemistry tool used to describe the degree to which an electron is localized in a molecule or solid. The calculation results show that the covalent bond has a greater confinement effect on electrons, and the difference in ELF between the two structures of HLOPC₆₀ and TLOPC₆₀ is small.

LOPC₆₀ is an all-carbon conjugated system with a large number of π electrons on the surface of the system, which makes LOPC₆₀ more likely to form π–π stacking interactions when it is in contact with the external environment. The nature of π–π stacking interactions has been shown to be dispersive interactions [44]. The van der Waals (vdW) potential [45] is crucial for studying dispersive interactions. The analysis of van der Waals potentials is mainly concerned with the negative region, that is, the part where the negative contribution corresponding to the dispersion attraction potential is greater than the positive contribution resulting from the exchange repulsion potential, so that the probe atoms will also bind to such regions. Helium is an inert gas, meaning that its chemical properties are very stable and that is does not easily react with other substances. This allows it to interact with the molecules under study without complex chemical interactions, thus more simply reflecting the characteristics of van der Waals interactions. So, the helium atom is used as the probe for the calculation. As shown in Figure 7A, the regions with a negative vdW potential in HLOPC₆₀ are distributed in the depressions outside the system and spherical spaces inside the fullerenes. In TLOPC₆₀, the vdW potential outside the system penetrates due to the different arrangement of fullerenes. The larger space between the fullerenes in TLOPC₆₀ allows probe atoms to bind deeper. The minimum point of the vdW potential outside the system is −1.6 kcal/mol for TLOPC₆₀ and −1.4 kcal/mol for HLOPC₆₀, because the minimum point in TLOPC₆₀ is attracted by more carbon atoms. The minimum point of the vdW potential inside the fullerenes of both systems is −2.9 kcal/mol, which is due to the same number of surrounding carbon atoms.

Finally, we investigated the interlayer interactions between the bilayer HLOPC₆₀ and TLOPC₆₀. Figure 7B shows the independent gradient model based on a Hirshfeld partition (IGMH) [46] map of bi-layer HLOPC₆₀ and TLOPC₆₀. IGMH can clearly describe the weak interaction between fragments and is defined as follows:

$$\delta g\left(r\right)=g^{IGM}\left(r\right)-g\left(r\right)$$

(3)

$$g\left(r\right)=\left|{\displaystyle \sum _i\nabla {\rho }_i\left(r\right)}\right|$$

(4)

$$g^{IGM}\left(r\right)={\displaystyle \sum _i\left|\nabla {\rho }_i\left(r\right)\right|}$$

(5)

The specific interpretation of Formulas (3)–(5) can be seen in the Supplementary Information. In Figure 7B, the interaction isosurface between the bilayer HLOPC₆₀ and TLOPC₆₀ is represented by a green isosurface, indicating van der Waals interactions. This demonstrates that the interaction is predominantly a dispersion-driven π–π stacking interaction. It can be seen that one layer of LOPC₆₀ is interleaved with another layer, which is due to the larger vdW potential in the recess, which has been discussed in the vdW potential section. At the same time, the vdW potential of the depression in TLOPC₆₀ is significantly stronger than that of HLOPC₆₀, so the interlayer interaction of bilayer TLOPC₆₀ should be stronger than that of HLOPC₆₀. We calculated the interaction energies of a single fullerene (C₆₀) adsorbed on HLOPC₆₀ and TLOPC₆₀ in a crystalline manner by energy decomposition analysis based on forcefield (EDA-FF) [47], and the results are shown in

Table 3. Interaction energies of single fullerenes adsorbed on HLOPC₆₀ and TLOPC₆₀ in the form of crystals.

Interactions	Bilayer HLOPC60 (kJ/mol)	Bilayer TLOPC60 (kJ/mol)
electrostatic	0.12	−0.32
repulsion	44.03	112.67
dispersion	−149.79	−247.60
total	−105.65	−135.25

. Since the region of action between fullerenes is obviously non-polar (i.e., the atomic charge is very small), their electrostatic interaction is almost zero, and the calculation accuracy based on force fields has certain limitations, resulting in small errors. It can be seen from the table that the main attraction between the two comes from the dispersive interaction, and the dispersive interaction in TLOPC₆₀ is clearly stronger than that in HLOPC₆₀, which also leads to a stronger interlayer interaction in the bilayer TLOPC₆₀. This is because the interlayer fullerenes of TLOPC₆₀ are more tightly bound, so the dispersion is stronger, and the repulsion is also enhanced.

To further highlight the potential of TLOPC₆₀ in optoelectronic applications, we compare its properties with those of two widely studied 2D materials, graphene and MoS₂. TLOPC₆₀ demonstrates unique optoelectronic properties and application potential. Graphene, due to its zero-bandgap semi-metallic nature, exhibits excellent electrical conductivity, but its lack of a bandgap significantly limits its application in optoelectronic devices, such as light absorption and charge separation. Additionally, MoS₂, which typically has a direct bandgap of approximately 1.8 eV in its monolayer form, is an ideal material for light absorption; however, its charge transport performance is limited by its high effective mass and relatively low carrier mobility.

In contrast, TLOPC₆₀ combines the advantages of both materials: its moderate bandgap of approximately 1.6 eV allows for both efficient light absorption and charge separation, while its low wave function symmetry significantly enhances the efficiency of charge transport. Particularly in terms of interlayer interactions, TLOPC₆₀ exhibits a higher electron density and a stronger negative potential energy density, ensuring greater stability in the interconnection between layers. These characteristics make TLOPC₆₀ advantageous for applications requiring efficient light absorption and charge transport.

4. Conclusions

In this work, we employed the periodic TDDFT algorithm to study the optoelectronic properties of two-dimensional fullerene arrays with two different stacking modes. The results reveal significant differences in the cross-space charge transfer performance, which is linked to the wave function symmetry. Specifically, the C–C bond connecting two five-membered rings in fullerenes acts as an efficient electron transport outlet due to its low wave function symmetry. Real-space analyses, including the electron density at critical points, quantitatively explained the stacking mechanisms and interlayer interactions of bilayer LOPC₆₀. Our findings show that TLOPC₆₀, with its higher electron density, negative potential energy density, and stronger interlayer interactions, offers greater structural stability and enhanced charge transport efficiency. These properties make the TLOPC₆₀ stacking mode more suitable for optoelectronic applications, such as solar cells and LEDs. Its moderate bandgap balances light absorption and charge transport, positioning it as an ideal candidate for high-performance device design. Furthermore, the theoretical insights provided here offer specific guidelines for synthesizing fullerene-based materials. The identification of TLOPC₆₀’s stacking mode can inspire experimental efforts to replicate similar configurations, while its strong interlayer interactions suggest strategies for designing intermediate layers in optoelectronic devices to improve the charge extraction efficiency and reduce recombination losses. This work lays the foundation for bridging theoretical predictions with experimental developments in fullerene-like optoelectronic materials.