Solution-processable small molecules (SMs) that can serve as donors in bulk-heterojunction (BHJ) solar cells are practical alternatives to their polymer counterparts. However, SM–fullerene blends commonly suffer severe voltage losses. In general, devices that reach open-circuit voltages (VOC) > 1 V yield low photocurrents in BHJ solar cells with fullerene acceptors (e.g., PC71BM) and modest power conversion efficiencies (PCEs). In this contribution, we report on the design, synthesis, and BHJ device characteristics of a new SM donor, 2F-DRCN5T, yielding a VOC of up to 1.10 V with PC71BM as the fullerene acceptor, while maintaining PCEs > 7% (over 8% achieved upon solvent-vapor-annealing (SVA) treatment). The negligible energy loss during charge generation (ΔECT), the deep-lying HOMO of 2F-DRCN5T inferred from its large ionization potential (IP), the high charge-transfer-state energy (ECT) of the blend, and a reduced nonradiative voltage loss account for the high VOC achieved in BHJ solar cells.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): CRG-R2-13-BEAU-KAUST-1
Acknowledgements: This publication is based upon work supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award CRG-R2-13-BEAU-KAUST-1. The authors acknowledge concurrent support under Baseline Research Funding from KAUST. T.D. acknowledges financial support from National Natural Science Foundation of China (21702202).