Alkylsilyl Fused Ring‐Based Polymer Donor for Non‐Fullerene Solar Cells with Record Open Circuit Voltage and Energy Loss

Abstract The energy loss (E_loss), especially the nonradiative recombination loss and energetic disorder, needs to be minimized to improve the device performance with a small voltage (V_OC) loss. Urbach energy (E_U) of organic photovoltaic materials is related to energetic disorder, which can predict the E_loss of the corresponding device. Herein, a polymer donor (PBDS‐TCl) with Si and Cl functional atoms for organic solar cells (OSCs) is synthesized. It can be found that the V_OC and E_loss can be well manipulated by regulation of the energy level of the polymer donor and E_U, which is dominated by the morphology. A low energetic disorder with an E_U of 23.7 meV, a low driving force of 0.08 eV, and a low E_loss of 0.41 eV are achieved for the PBDS‐TCl:Y6‐based OSCs. Consequently, an impressive open circuit voltage (V_OC) of 0.92 V is obtained. To the best of knowledge, the V_OC value and E_loss are both the record values for the Y6‐based device. These results demonstrate that fine‐tuning the polymer donor by functional atom modification on the side chain is a promising way to reduce E_U and energy loss, as well as obtain small driving force and high V_OC for highly efficient OSCs.