High-Performance Ternary Organic Photovoltaics Incorporating Small-Molecule Acceptors with an Unfused-Ring Core

Abstract

Organic photovoltaics (OPVs) have made enormous progress in recent years, benefiting from the rapid development of non-fullerene acceptors (NFAs). Most high-performance NFAs, however, have featured π-conjugated backbones with large-fused core structures, increasing the complexity and cost of their synthesis and limiting their practical commercialization. In this study, we synthesized a series of acceptor–donor–acceptor-configured small-molecule acceptors (NTCPDTCN, NTCPDTID, and NTCPDT2F) based on a core structure featuring a naphthobisthiadiazole (NT) group and two cyclopenta[2,1-b,3,4-b′]dithiophene (CPDT) groups as the unfused-ring central unit and equipping malononitrile (CN), 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (ID), and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (2F) groups as terminal groups. When blended with PM7, the NTCPDTCN-containing binary device displayed a high open-circuit voltage (V OC) of 1.04 V, without self-aggregation, as well as the best device performance. When blended with PM6:Y6, the ternary NTCPDTCN-, NTCPDTID-, and NTCPDT2F-based OPVs provided power conversion efficiencies of 15.4 ± 0.09, 14.6 ± 0.15, and 16.0 ± 0.08%, respectively. NTCPDT2F provided complementary absorption and allowed fine-tuning of the blend morphology, resulting in suppression of charge recombination and improvements in charge generation and collection, thereby achieving the highest device performance. Thus, our findings might provide some directions for developing high-performance ternary OPVs through the introduction of unfused-ring small-molecule acceptors.

The role of unfused-ring-based small-molecule acceptors as the third component in ternary organic photovoltaics

“…Certainly, as the core structure of NTz presents a notably elevated LUMO energy level due to its relatively weaker electron-deficient property as compared to that of NT-based NFAs which were reported in our previous study. 29 This result indicates that the NTz-based NFAs are beneficial for adjusting the energy level of the acceptor alloy phase, potentially resulting in a lower energy loss. 33,34 Additionally, the higher LUMO level of the NTz-based molecules as the acceptor which blended with the donor, giving low energy offset, thereby promoting hybridization between charge transfer and the lowest acceptor excited state that leads to the effective suppression of the nonradiative voltage loss.…”

“…Li's group has reported that the binary device selected the donor of PBDB-T, blended with NTzbased acceptors NTzCPDTID and NTzCPDT2F, 30 giving moderate PCE of 6.19% and 8.08% which are better than those OPV with the related NT-based system. 29 Notably, the underlying potential performance of the NTz-based ternary OPVs has not yet been comprehensively explored. Therefore, our work focuses on studying ternary device performance using NTz-based molecules as guest acceptors.…”

Inorganic/Organic Electron Transport Interface Engineering for Planar and Fiber-Shaped Organic Solar Cells

“…In particular, using CPE-modified ZnO/wires helped improve the coverage of the P3HT:PCBM film and reduce the energy barrier at ZnO and P3HT:PCBM, leading to improvements in J SC and FF. As a result, our interface modification approach combined with highly efficient active layer materials, such as PM6:Y6, PM6:ITIC-Th, PM6:BTP-eC9, and PSe-HD:Y6, could be an efficient strategy for the development of high-performance planar and fiber-shaped OSCs in the near future. There are some reports on the i OSCs based on the use of non-fullerene acceptors and new highly efficient active layer coating on top of the ZnO ETL, similar to our work. ,− Therefore, we highly believe that our approach of manipulating the electron transport interfaces can be applied to a broad range of hydrophobic organic photoactive layers, including those based on non-fullerene acceptors and new donor–acceptor molecules, which share similarities with our P3HT:PCBM system.…”

Design and synthesis of non-fused non-fullerene acceptors containing naphthobisthiadiazole for organic solar cells

“…We note that the overall photovoltaic performances of the cells derived from these two acceptors are moderate, and they might need to be integrated with more appropriate electron-donating polymers to enhance the photovoltaic parameters. 44,45 The detailed photovoltaic parameters are summarized in Table 2. The slightly higher J SC of the device based on NTIC-4Cl can be further confirmed by the current density values integrated from the external quantum efficiency (EQE) spectra (Fig.…”