All-Small-Molecule Ternary Organic Solar Cells with 16.26% Efficiency Enabled by Iodinated Electron Acceptor

Abstract

All-small-molecule organic solar cells (ASM-OSCs) face significant challenges in achieving an ideal morphology for efficient charge generation and transport, primarily due to the inherent phase separation issues within the active layer. Herein, we developed efficient ASM-OSCs by incorporating an iodinated electron acceptor BO-4I into the BTR-Cl:Y6 host binary system. The favorable intermolecular interaction of BO-4I and its excellent miscibility with both the donor and acceptor components contributed to a controllable morphology formation process of active layer, resulting in a pronounced phase separation structure. Consequently, the ternary ASM-OSCs with 5 wt% BO-4I achieved an improved power conversion efficiency (PCE) of 16.26%, observably outperforming the binary BTR-Cl:Y6-based devices. Furthermore, in-situ morphological and charge carrier dynamics studies confirmed the critical role of BO-4I in enhancing the device performance by optimizing the morphology, particularly through improved crystallinity. This work provides valuable insights into the potential of iodinated electron acceptors in advancing high-performance ASM-OSCs, offering a strategic pathway for development of high-performance organic photovoltaic devices.