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Fullerene's ring: A new strategy to improve the performance of fullerene organic solar cells
摘要： Fullerene is a common acceptor of organic solar cells (OSCs), therefore, it is of great significance to improve the performance of fullerene OSCs. Meanwhile, π-π stacking plays a crucial part in charge transfer and transport, so improving π-π stacking of fullerene OSCs is vital for achieving high efficiency in OSCs. In this work, we report a new strategy of adding [9]cycloparaphenylene ([9]CPP) as the third component in active layers, which affects the π-π stacking and improves the short-circuit current density (JSC) and fill factor (FF). As a result, a high power conversion efficiency (PCE) of 11.03% was obtained in PTB7-Th:[9]CPP:PC71BM ternary OSCs, which is nearly 20% higher than that of binary devices. At the same time, after [9]CPP is added PBDB-T:PC71BM and PTB7-Th:PCBM binary OSCs the PCE increases by 20% and 10% respectively. [9]CPP and fullerene acceptors formed [9]CPP?fullerenes system due to concave-convex π-π interactions, which was verified by density functional theory (DFT), and this system is first reported in OSCs. [9]CPP?fullerenes system affects the π-π stacking of acceptors, not only promotes charge transfer between donor and acceptor, but also enhances charge transport between the acceptor, thus improving the JSC. Furthermore, with the help of [9]CPP?fullerene system, the whole film is formed a nano-inter-transmission network, obtained a better appearance and improved FF. The results show that encapsulating fullerene of [9]CPP is indeed a resultful strategy for improving the performance of fullerene OSCs.
关键词： organic solar cells,cycloparaphenylenes,fullerene acceptors,ternary solar cell
更新于2025-09-19 17:13:59
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Solid-state order and charge mobility in [5]-[12] cycloparaphenylenes
摘要： We report a computational study of mesoscale morphology and charge transport properties of radially π-conjugated cycloparaphenylenes [n]CPPs of various ring sizes (n = 5-12, where n is the number of repeating phenyl units). These molecules are considered as structural constituents of fullerenes and carbon nanotubes. [n]CPP molecules are nested in a unique fashion in the solid state. Molecular dynamics simulations show that while intramolecular structural stability (order) increases with system size, intermolecular structural stability reduces. Density functional calculations reveal that reorganization energy, an important parameter in charge transfer, decreases as n is increased. Intermolecular charge-transfer electronic couplings in the solid state are relatively weak (due to curved π-conjugation and loose intermolecular contacts) and are on the same order of magnitude (i.e., ~10 meV) for each system. Intrinsic charge-carrier mobilities were simulated from kinetic Monte Carlo simulations; hole mobilities increased with system size and scaled as ~n4. We predict that disordered [n]CPPs exhibit hole mobilities as high as 2 cm2/Vs. A strong correlation between reorganization energy and hole mobility, i.e. μ~λ?4, was computed. Quantum mechanical calculations were performed on co-facially stacked molecular pairs for varying phenyl units and revealed that orbital delocalization is responsible for both decreasing reorganization energies and electronic couplings as n is increased.
关键词： kinetic Monte Carlo simulations,charge transport,density functional calculations,molecular dynamics,cycloparaphenylenes
更新于2025-09-04 15:30:14