Enhancing Photon Utilization Efficiency for High-Performance Organic Photovoltaic Cells via Regulating Phase Transition Kinetics.

Efficient photon utilization is key to achieving high-performance organic photovoltaic (OPV) cells. In this study, we constructed a multiscale fibril network morphology in a PBQx-TCl:PBDB-TF:eC9-2Cl-based system by regulating donor and acceptor phase transition kinetics. The distinctive phase transition process and crystal size were systematically investigated. PBQx-TCl and eC9-2Cl formed fibril structures with diameters of approximately 25 nm in ternary films. Additionally, fine fibrils assembled by PBDB-TF were uniformly distributed over the fibril networks of PBQx-TCl and eC9-2Cl. The ideal multiscale fibril network morphology enables the ternary system to achieve superior charge transfer and transport processes compared to binary systems; these improvements promote enhanced photon utilization efficiency. Finally, we achieved a high power conversion efficiency of 19.51% in a single-junction OPV cell. The external quantum efficiency of the optimized ternary cell exceeded 85% over a wide range of 500-800 nm. We also fabricated a tandem OPV cell to increase solar photon absorption. The tandem cell had an excellent PCE of more than 20%. This study provides guidance for constructing an ideal multiscale fibril network morphology and improving the photon utilization efficiency of OPV cells. This article is protected by copyright. All rights reserved.