A systematic approach involving conjugation extension and end group chlorination is capable of enhancing both JSC and PCE. Overall, the PM6:DTTC-4Cl-based device delivers a remarkable PCE of 15.42% with a VOC of 0.92 V, a JSC of 22.64 mA cm−2 and an FF of 74.04%.

Improving power conversion efficiencies (PCEs) and stability are two main tasks for organic photovoltaic (OPV) cells. In the past few years, although the PCE of the OPV cells has been considerably improved, the research on device stability is limited. Herein, a cross‐linkable material, cross‐linked [6,6]‐phenyl‐C61‐butyric styryl dendron ester (c‐PCBSD), is applied as an interfacial modification layer on the surface of zinc oxide and as the third component into the PBDB‐TF:Y6‐based OPV cells to enhance photovoltaic performance and long‐term stability. The PCE of the OPV cells that underwent the two‐step modification increased from 15.1 to 16.1%. In particular, such OPV cells exhibited much better stability under both thermal and air conditions because of the decreased number of interfacial defects and stable interfacial and active layer morphologies. The results demonstrated that the introduction of a cross‐linkable fullerene derivative into the interfacial and active layers is a feasible method to improve the PCE and stability of OPV cells.

In this article, a fluorinated heptacyclic dithienocyclopentacarbazole (DTC)-based non-fullerene acceptor (NFA), DTC­(4Ph)-4FIC, is synthesized and blended with J71, PBDB-T, and PBDB-TF, featuring complementary absorption and well-matched energy levels. The DTC­(4Ph)-4FIC neat film exhibits face-on preference, whereas the nonfluorinated counterpart, DTC­(4Ph)-IC, exhibits edge-on preference; this unique feature owing to fluorination in DTC-based NFAs is observed for the first time. More importantly, DTC­(4Ph)-4FIC exhibits improved power conversion efficiencies (PCEs) of 10.92 and 10.41% in J71- and PBDB-T-containing devices, while the devices that employed DTC­(4Ph)-IC afford PCEs of 7.76 and 9.48%, respectively. Because PBDB-TF is known to exhibit lower energy levels than J71 and PBDB-T, the corresponding device affords a V OC of 0.95 V, a J SC of 18.29 mA cm–2, a FF of 75.70%, and a PCE of 13.15%, which is 20 and 26% higher than J71- and PBDB-T-containing devices. Furthermore, the inverted device containing the PBDB-TF:DTC­(4Ph)-4FIC blend is fabricated using cross-linkable fullerene (C-PCBSD) as the cathode interlayer, affording a decent PCE of 13.36%, with a V OC of 0.94 V, a J SC of 20.20 mA cm–2, and a FF of 70.42%.

In this study, two dithieno­[3,2-b]­thiophenecyclopentacarbazole (DTTC)-based nonfullerene acceptors (NFAs) named DTTC-4F-C8 and DTTC-4Cl-C9 are designed, synthesized, and incorporated as the second acceptors in PM6:Y6 binary blend to explore the performance of the ternary organic solar cells (OSCs). By incorporating a small amount of DTTC-4F-C8/DTTC-4Cl-C9 into the PM6:Y6 binary blend as the second acceptor, we achieved an elevated efficiency of 16.05%/16.55%, with simultaneously enhanced open-circuit voltage (V OC), short-circuit current-density (J SC), and fill factor (FF) values. Because of the compatibility differences between the second acceptor DTTC-4F-C8/DTTC-4Cl-C9 and the host materials PM6 and Y6, despite having comparable energy levels for the two NFAs, different photovoltaic performances are observed for the resultant ternary OSCs. The results indicate that the ternary OSCs incorporating carbazole-based NFAs DTTC-4F-C8/DTTC-4Cl-C9 as a second acceptor is a constructive method to enhance the performance of the PM6:Y6 binary host.