An Asymmetric Non‐fullerene Acceptor with Low Energy Loss and High Photovoltaic Efficiency

Abstract

Minimizing energy loss (E loss ) plays a key role in improving the power conversion efficiencies (PCEs) of organic solar cells (OSCs). Here, to reveal the feasibility of the asymmetric molecular strategy in designing high-efficiency and low E loss OSC materials, we adopt the alkyl-alkoxy modification to design an asymmetric non-fullerene acceptor (NFA) named OC8-4F, where its symmetric alkyl-and alkoxy-substituted counterparties (2OC8-4F, eC9-4F) are also prepared. The results suggest that the introduction of a symmetric alkoxy at the edge of eC9-4F can effectively decrease the lowest unoccupied molecular orbit level without greatly changing the highest occupied molecular orbit level, leading to a mediated bandgap. In the devices, the OC8-4F possesses well-balanced charge generation and E loss , giving the highest PCE of 18%. Our results imply that finely tuning the asymmetric structure can be used as an effective molecular design strategy to improve the photovoltaic performance of OSCs.

Long-Range Charge Separation Enabled by Intramoiety Delocalized Excitations in Copolymer Donors in Organic Photovoltaic Blends

“…The iDEs may diffuse through a long-range Förster energy transfer mechanism to form the xCT states first, which, however, is unlikely to be the case here. For the xCT-mediated channel, the ESA feature at ∼900 nm gradually shifts to the longer wavelength side to ∼940 nm (Figure b) due to the modified electric field caused by increased electron–hole separation, which strongly modulates the optical response by influencing neighboring molecules as previously discussed in OPV systems. ,,− Such a spectral shift is not observed for the iDE-mediated channel (Figure d). The ESA feature that emerges at ∼940 nm is similar to the spectral feature of free charges, suggesting that the electron and hole is readily separated upon the conversion from iDEs in the polymer PM6.…”

Designing of Thiophene [3, 2-b] Pyrrole Ring-Based NFAs for High-Performance Electron Transport Materials: A DFT Study

“…From the open-circuit voltage values, the energy loss for the studied molecules was also evaluated so that the probable energy that might be lost could be taken into account beforehand. For this purpose, the E loss = eV OC ( 62 ) formula was utilized, and the values are compiled in Table 11 . Here, the lowest energy loss among all seems to be of the TP4 molecule, which is quite lower than the reference molecule itself.…”

Synthesis of Long‐Chain Oligomeric Donor and Acceptors via Direct Arylation for Organic Solar Cells†

“…In recent years, unfused‐ring acceptors (UFRAs) have attracted numerous attention due to their structural simplicity and synthetic easiness. [ 25‐28 ] By introducing conformation locks ( e.g ., F···H, S···N, O···S, and F···S non‐covalent intramolecular interactions), UFRAs can exhibit comparable geometries, stacking models, carrier mobilities, and thus device performances with FREAs. [ 29‐35 ]…”