Spin-Dependent Recombination Pathways Revealed by Magnetoconductance in Annealed Polymer–Fullerene Bulk Heterojunction Solar Cells

This work presents a systematic solution-state investigation of non-covalent interactions between pristine C70 fullerene and polystyrene (PS) in benzene, addressing a notable gap in polymer–fullerene research where C70 systems have been far less explored than their C60 counterparts. UV–Vis absorption spectroscopy, supported by symmetry-based (D5h) transition analysis, was employed to examine C70/benzene, PS/benzene, and PS/C70/benzene solutions over a controlled range of fullerene concentrations. The characteristic absorption bands of C70 were found to retain their spectral positions upon incorporation into the PS matrix, confirming the absence of covalent bonding and the preservation of the intrinsic π-electronic structure of the fullerene. In contrast, absorption intensities and the optical absorption edge were sensitively modulated by the polymer environment. Optical bandgap energies (Eopt), extracted via Tauc analysis, exhibit a non-monotonic dependence on C70 concentration, reflecting the competition between PS–C70 and C70–C70 interactions mediated by π–π stacking and van der Waals forces. The novelty of this study lies in demonstrating that weak, non-covalent polymer–fullerene interactions alone can induce measurable, reversible tuning of the optical bandgap without altering molecular electronic structure. These findings establish concentration control in π-conjugated polymer solutions as an effective, non-chemical strategy for bandgap engineering in polymer–fullerene systems.

The theoretical description of the effect of the temperature on the mobility is yet a matter of controversy related to charge transport in disordered organic semiconductors. In this paper, charge transport in the blend of polymer PDPP5T and fullerene PC 61 BM is investigated. We show that the temperature dependent current density versus voltage characteristics of a hole-only device based on PDPP5T:PC 61 BM blend can be better described by using the improved extended Gaussian disorder model (IEGDM) than the extended Gaussian disorder model (EGDM). The extracted values of the width of the Gaussian density of states σ from the two models are the same and observed to fall in the range of typical values. However, the extracted value of average intersite distance a from the IEGDM is smaller than that from the EGDM, indicating that the IEGDM provides a more significantly electric field dependence of the mobility than the EGDM. Furthermore, the IEGDM provides a more satisfactory description of the relationship between the low-field carrier mobility and temperature than the EGDM. These results indicate that the effect of the Arrhenius temperature dependence on charge transport in disordered organic semiconductors is crucial.

Abstract The adsorption energy of oxygen onto the Pt atoms bound to carbon substrates, such as one-dimensionally polymerized C60 and Li@C60 molecules, was investigated using density functional theory calculations. The oxygen adsorption energy varies depending on the bonding structure between Pt and carbon atoms. The local density of states (LDOS) center of the Pt 5d orbitals and the oxygen adsorption energy exhibited linear relationships, showing a decrease in the magnitude of oxygen adsorption energy with a downward shift of LDOS center of the Pt atoms bound to the one-dimensionally polymerized fullerene molecules. The study findings suggest that a suitable Pt-carbon bonding structure should be selected to improve the oxygen reduction reaction activity of Pt catalysts, whose bonding strength with oxygen is influenced by the supporting carbon atoms.

Fullerene dimers are fullerene polymers formed by two fullerene molecules either directly connected or via a bridging skeleton. They are expected to have important applications in fields such as photovoltaic, catalysis, single-molecule electronics, and supra-molecular chemistry. Previously reported syntheses of fullerene dimers mainly under mechanical milling conditions or FeCl3-mediated solution-phase synthesis conditions. Here, we developed a universal method for synthesizing fullerene dimers, which can obtain various types of fullerene dimers with different sizes and different connection angles. Moreover, by using different types of fullerenes as reaction materials, precise control of dimer lengths of different sizes can be achieved, providing diverse options for applications with special requirements for fullerene molecule size in the future.

Metal-free photoelectrocatalysts of the oxygen reduction reaction (ORR) composed of electroreduced graphene oxide (ERGO), donor polymer P3HT and fullerene acceptor C60(CF3)H are described. We have shown that the utilization an ERGO interface layer is beneficial for the design of the efficient and stable ORR photoelectrodes. FTO-coated glass substrates (fluorine-doped tin oxide) were used for the photoelectrodes fabrication. A thin layer of graphene oxide was deposited by spin-coating at the FTO surface following by its electrochemical reduction to form ERGO layer. Then, a bulk heterojunction (BHJ) layer of P3HT and C60(CF3)H was deposited at FTO/ERGO surface via spin-coating following by its annealing to form the photoelectrode FTO/ERGO/BHJ. ORR catalytic activity of the fabricated FTO, FTO/ERGO, FTO/BHJ, and FTO/ERGO/BHJ photoelectrodes was compared using cyclic voltammetry (PBS, pH=7.4; white light irradiation, 100 mW cm–2). The FTO/ERGO photoelectrode demonstrates the ORR electrocatalytic behavior. For the FTO/ERGO photoelectrode, the ORR current density increases by 27 times, and the overpotential decreases by 0.1 V compared to the values for the FTO photoelectrode. The FTO/BHJ and FTO/ERGO/BHJ photoelectrodes have a pronounced photocatalytic effect. The irradiation of the FTO/BHJ and FTO/ERGO/BHJ photoelectrodes with white light increases the ORR current density more than 2 and 3 times, respectively, compared with the values for the FTO/ERGO photoelectrode. The overpotential is reduced by 0.3 V. Chronoamperometric studies have shown that the FTO/ERGO/BHJ photoelectrode works stably for more than 20 h, while the FTO/BHJ photoelectrode undergoes peeling of the BHJ photoactive film. The hybrid FTO/ERGO/BHJ photoelectrodes are high-efficient ORR photoelectrocatalysts with decreased overpotential (similar with that for the efficient metal-containing electrocatalysts of the non-platinum group), and operating lifetime of more than 20 h. Deposition of ERGO layer at the FTO surface improves the adhesion of the photoactive layer while maintaining high charge-transport characteristics. Thus, the engineering of the long-lifetime polymer-based ORR photoelectrodes is possible via introduction of the ERGO interface layer between photoactive BHJ and FTO layers. For citation: Malkin N.A., Brotsman V.A., Lukonina N.S., Goryunkov A.A. Hybrid photoelectrocatalyst for molecular oxygen reduction based on reduced graphene oxide and P3HT:C60(CF3)H. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 9. P. 90-98. DOI: 10.6060/ivkkt.20256809.1y.

2D polymeric fullerene scaffolds, composed of covalently bonded superatomic C60 nanoclusters, are emerging semiconductors possessing unique hierarchical electronic structures. Hitherto their synthesis has relied on complex and time-consuming reactions, thereby hindering scalable production and limiting the technological relevance. Here, the study demonstrates a facile electrochemical exfoliation strategy based on the intercalation and expansion of a layered fullerene superlattice, to produce large size (≈52.5 µm2) and monolayer thick 2D polymeric C60 with high exfoliation yield (≈83%). In situ reduction of solvated protons (H+) weakens the interlayer interactions thereby promoting the rapid and uniform intercalation of tetra-n-butylammonium (TBA+), ensuring gram-scale throughput and high structural integrity of exfoliated 2D polymeric C60. As a proof of concept, the solution-processed 2D polymeric C60 nanosheets have been integrated into thin-film photodetectors, exhibiting a broad spectral photoresponse ranging from 405 to 1200 nm, with a peak photocurrent at 850 nm and a stable response time. This efficient and scalable exfoliation method holds great promise for the advancement of multifunctional composites and optoelectronic devices based on 2D polymeric C60.

This work rigorously explores a Blended Heterojunction (BHJ) Organic Solar Cell (OSC) using a blend of Donor/Acceptor (D/A) fullerene polymers (PCDTBT and PCBM) as the photoactive absorber layer. The proposed OSC has been implemented and modeled using the ATLAS tool of Silvaco TCAD, a widely used commercial software. The thin heterojunction photoactive absorber layer of blended PCDTBT: PCBM D/A polymers increase the diffusion length causing a significant reduction in the Langevin recombination and hence, enhance the Power Conversion Efficiency (PCE). The hole transport is enhanced by a thin layer of PEDOT: PSS, an organic blended polymer. As anode and cathode, Indium Tin Oxide (ITO), a transparent conductive oxide, and Aluminum (Al) are used. The modeling of the OSC has considered the effects of singlet dissociation and recombination, and the Langevin recombination for accuracy and better physical insight. The electrical simulations of the proposed OSC carried out in the Silvaco environment resulted in improved current-voltage characteristics, which demonstrate a high open circuit voltage (0.965 V), an impressive fill factor (66.717%), a moderate short circuit current density (10.505 mA/cm2), and an enhanced PCE (6.766%). The optical simulations of the proposed OSC demonstrate its external quantum efficiency of more than 25% over the wavelength span of 380–1500 nm.

Organic π-conjugated materials exhibit exceptional nonlinear optical (NLO) properties due to their unique electronic structures, characterized by short response times and large NLO responses. Fullerene (C60) is one of the few polymer species that possess a rich π-conjugated system, making it a promising material with significant NLO responses. In the present paper, we designed three C60 polymer fragments and employed density functional theory to estimate their molecular static first and second hyperpolarizabilities. Compared to previously reported fullerene derivatives, the designed C60 polymer fragments can exhibit notable second-order and third-order molecular NLO responses. The study shows that the hyperpolarizabilities and energy gaps of the investigated C60 polymer fragments are greatly influenced by their topological structures and bonding modes. These findings provide new insights for the design of novel NLO materials based on C60 polymers, and the realization of tunable NLO responses in C60 cluster-based molecular systems, which may have significant applications in nanophotonic devices.

The charge carrier formation and transport in the pristine polymers as well as in the polymer–fullerene blend is still a hot topic of discussion for the scientific community. In the present work, the carrier generation in some prominent organic molecules has been studied through ultrafast transient absorption spectroscopy. The identification of the exciton and polaron lifetimes of these polymers has led to device performance-related understanding. In the Energy Gap Law, the slope of the linear fit gradient (γ) of lifetimes vs. bandgap are subjected to the geometrical rearrangements experienced by the polymers during the non-radiative decay from the excited state to the ground state. The value of gradient (γ) for excitons and polarons is found to be −1.1 eV−1 and 1.14 eV−1, respectively. It suggests that the exciton decay to the ground state is likely to involve a high distortion in polymer equilibrium geometry. This observation supports the basis of Stokes shift found in the conjugated polymers due to the high disorder. It provides the possible reasons for the substantial variation in the exciton lifetime. As the bandgap becomes larger, exciton decay rate tends to reduce due to the weak attraction between the holes in the HUMO and electron in the LUMO. The precise inverse action is observed for the polymer–fullerene blend, as the decay of polaron tends to increase as the bandgap of polymer increases.

The introduction of a third component to a donor–acceptor blend binary device can boost the performance of organic solar cells. This study investigated the role of a second polymer donor (D2, the third component) in the operation of polymer–fullerene blend solar cells in terms of the spatial distribution of D2 in the ternary active layer, which was visualized using photoconductive atomic force microscopy (PC-AFM). Ternary devices that consisted of a low-bandgap polymer, poly[(4,4-bis(2-ethylhexyl)-dithieno[3,2-b:2′,3′-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7 diyl] (PSBTBT), serving as D2, a wide-bandgap polymer donor, poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(2,2-ethyl-3(or4)-carboxylate-thiophene)] (PTO2), and a fullerene acceptor, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), utilized as host materials, were prepared at different PSBTBT loading amounts. The photocurrent images obtained using PC-AFM with selective illumination of PSBTBT and nonselective white-light illumination were compared to distinguish the photocurrents of PSBTBT from those of all the components. The comparison indicated that the photogenerated hole transport channels of PSBTBT were formed without a distinct phase separation from PTO2. The functional nanomorphology visualized by PC-AFM provides insights into the evolution of the open-circuit voltage and fill factor of the PSBTBT:PTO2:PCBM ternary device due to the increased PSBTBT loading.

Tunable and switchable magnetoresistance of P3HT:PCBM organic framework

In this study, we investigated the spectral functions of quasi-one-dimensional electronic systems realized in metallic fullerene polymers theoretically. We applied the multichannel bosonization method to the electronic band structures derived from two different atomic models of fullerene polymers. Both the obtained analytical formulation and numerical calculations revealed significant differences between the two models in the energy dependence of the spectral functions, despite the slight difference in their atomic arrangement. These results indicate that the precise atomic arrangement of synthesized fullerene polymers can be determined using spectral function data obtained by angle-resolved photoemission spectroscopy.

Construction of two-dimensional (2D) materials using fullerenes as building blocks has attracted particular attention, primarily due to their ability to integrate desired functionalities into devices. However, realization of stable 2D phases of polymerized fullerenes remains a big challenge. Here, we propose two stable 2D monolayer phases with covalently bridged C80 cages, namely α-C80-2D and β-C80-2D, which are semiconductors with strong absorption in the long wave range and appreciable carrier mobility, respectively. The high stability originates from the bond energy released by the [2+2] cycloaddition polymerization of C80 is greater than the deformation energy of a cage. Starting from α-C80-2D, endohedral incorporation of the Sc3N molecule into each C80 cage leads to 2D semiconductors of α-Sc3N@C80-2D and α'-Sc3N@C80-2D, which possess exceptional stability and diverse physical properties, including unique electronic band structures, strong optical absorption in the visible (VIS) to near-infrared (NIR) regime, and anisotropic optical characteristics. Remarkably, a temperature-induced order-disorder transition in the α-Sc3N@C80-2D phase has been observed at elevated temperatures above 600 K. These findings expand the family of 2D carbon materials and provide useful clue for the potential applications of fullerene-assembled monolayer networks.

The recent synthesis of monolayer fullerene networks (Hou, L., et al. Nature 2022, 606, 507) provides new opportunities for photovoltaics and photocatalysis because of their versatile crystal structures for further tailoring of electronic, optical, and chemical function. To shed light on the structural aspects of the photocatalytic water splitting performance of fullerene nanomaterials, we compare the photocatalytic properties of individual polymeric fullerene chains and monolayer fullerene networks from first-principles calculations. We find that the photocatalytic efficiency can be further optimized by reducing the dimensionality from two-dimensional (2D) to one-dimensional (1D). The conduction band edge of the polymeric C60 chain provides an external potential for the hydrogen reduction reaction much higher than that of its monolayer counterparts over a wider range of pH values, and there are 2 times more surface active sites in the 1D chain than in the 2D networks from a thermodynamic perspective. These observations identify the 1D fullerene polymer as a more promising candidate as a photocatalyst for the hydrogen evolution reaction in comparison to monolayer fullerene networks.

Abstract In this paper, the thermal stability and degradation mechanisms of C60 fullerene‐based polymers, obtained by click polymerization between dialkyne‐substituted C60 derivative monomers and 1,3,5‐tris(dodecyloxy)benzene‐based diazide comonomers, were evaluated. The activation energy of the fullerene polymer C60P2 with an ethylene spacer, determined under peak degradation rate conditions, was lower than that of the counter polymer C60P1 with a methylene spacer, suggesting lower thermal stability of C60P2. The combined technique of thermogravimetric analysis—mass spectroscopy and Fourier transform infrared spectroscopy revealed that the thermal decomposition onset of the analyzed samples is accompanied by CC cleavage of the dodecyloxyside chain groups, followed by the decomposition of the 1,2,3‐triazole, dicarboxylate and benzoate moieties. It was found that no thermal decomposition of the fullerene carbon cage occurs up to 670°C. Molecular modeling with Hyperchem software version 7.5 confirmed that C60P1 is more thermally stable than C60P2.

A composite of iron oxide magnetic nanoparticles and coordination fullerene polymer (C60 Pd3 )n is formed by chemical deposition of spherical polymer nanoparticles on iron oxide magnetic nanoparticles in benzene containing C60 and Pd(0) complex. The composition of the composite can be controlled by the amount of magnetite and concentration of polymerization precursors as well as the time of polymerization. The magnetic composite material Fe3 O4 -γFe2 O3 /(C60 Pd3 )n is used as a model system to investigate its deposition on a magnetic electrode and its electrochemical properties. The iron oxide magnetic nanoparticles ensure both the magnetic activity of the composite and its nanostructured morphology. Both of these factors are responsible for the enhancement of the electrochemical activity of the polymer phase forming the composite in comparison to the pure polymer material deposited on the same magnetic electrode. In the magnetic field of the electrode, the composite undergoes permanent and strong bonding with the surface of the electrode. The nanostructured morphology of the Fe3 O4 -γFe2 O3 /(C60 Pd3 )n composite also provides very good capacitive properties.

Monolayer fullerene network: A promising material for VOCs sensor

The performance of organic solar cells has been remarkably improved recently, where the cell structures are important for achieving high efficiency and stability. The formation and accumulation of long-lived charges in the cells are critical for the efficiency and stability of the cells; however, their relations with the cell structures have not yet been clarified from a microscopic viewpoint. Here, we report the microscopic mechanism of high efficiency and stability of inverted polymer fullerene solar cells compared to conventional cells even though the same photoactive layers are utilized. We directly observe the formation and accumulation of long-lived charges in these cells with electron spin resonance at a molecular level. We find the reduced effects of the formation and accumulation of long-lived charges in the inverted cells on their efficiency and stability compared to the case of conventional cells. These findings provide a striking advance in fundamental understanding, which is useful for further clarifying the operation mechanism of organic solar cells as well as further improving their efficiency and stability.

The understanding of the fundamental relationships betweenchemicalbonding and material properties, especially for carbon allotropeswith diverse orbital hybridizations, is significant from both scientificand applicative standpoints. Here, we elucidate the influence of theintermolecular covalent bond configuration on the mechanical and thermalproperties of polymerized fullerenes by performing systematic atomisticsimulations on graphullerite, a newly synthesized crystalline polymerof C60 with a hexagonal lattice similar to that of graphene.Specifically, we show that the polymerization of C60 moleculesinto two-dimensional sheets (and three-dimensional layered structures)offers tunable control over their mechanical and thermal propertiesvia the replacement of weak intermolecular van der Waals interactionsbetween the fullerene molecules with strong sp3 covalentbonds. More specifically, we show that graphullerite possesses highlyanisotropic mechanical as well as thermal properties resulting fromthe variation in the chemical bonding configuration along the differentdirections. In terms of their mechanical properties, we find thatgraphullerite can be remarkably ductile if strained along a certaindirection with oriented double bonds connecting the fullerenes. Combinedwith their drastically reduced Young’s modulus and bulk modulusas compared to graphite, these materials have the potential to beutilized in flexible electronics and advanced battery electrode applications.In terms of their thermal properties, we show that the bonding orientationdictates the intrinsic phonon scattering mechanisms, which ultimatelydictates their anisotropic temperature-dependent thermal conductivities.Taken together, their flexible nature combined with their remarkablyhigh thermal conductivities as polymeric materials positions themas ideal candidates for a plethora of applications such as for thenext generation of battery electrodes.