Suppressing electrostatic potential fluctuations to achieve high-efficiency organic photovoltaic cells for laser wireless energy transfer†

Abstract

Innovative molecular design strategies have significantly enhanced the power conversion efficiency (PCE) of organic photovoltaic (OPV) cells. Controlling monomeric electrostatic potential fluctuations (ESPFs) improves the PCE by achieving a high fill factor (FF), yet current studies largely neglect ESPF changes after aggregation. Here, we designed and synthesized three wide-bandgap acceptors, named AITO-Br, AITO-2F, and ITO-2F. Theoretical calculation results indicate that molecular aggregation leads to delocalization of π electrons, causing the ESPF of dimers to redistribute. Consequently, the AITO-2F molecule shows a minimal Stokes shift, temperature dependence, and energy disorder due to its low dimer ESPF. Furthermore, blending with PBQx-TCl, AITO-2F also retains the superior optoelectronic properties in blended films. Ultimately, OPV cells based on PBQx-TCl:AITO-2F achieved a PCE of 16.1%, accompanied by a high FF of 0.803. Notably, this is the highest efficiency for wide-bandgap acceptors with a bandgap below 750 nm. Transient absorption indicates that AITO-2F's low ESPF promotes intra-moiety excited states, enhancing exciton dissociation and reducing recombination. Under a 660 nm laser, PBQx-TCl:AITO-2F-based cells achieve a remarkable FF of 0.838 and a PCE of 36.4%, highlighting its potential in laser wireless energy transfer and the Internet of Things applications. This work presents a molecular design strategy by regulating aggregated ESPFs, paving the way for developing high-performance OPV materials.