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

The energy loss (Eloss ), especially the nonradiative recombination loss and energetic disorder, needs to be minimized to improve the device performance with a small voltage (VOC ) loss. Urbach energy (EU ) of organic photovoltaic materials is related to energetic disorder, which can predict the Eloss 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 VOC and Eloss can be well manipulated by regulation of the energy level of the polymer donor and EU , which is dominated by the morphology. A low energetic disorder with an EU of 23.7 meV, a low driving force of 0.08 eV, and a low Eloss of 0.41 eV are achieved for the PBDS-TCl:Y6-based OSCs. Consequently, an impressive open circuit voltage (VOC ) of 0.92 V is obtained. To the best of knowledge, the VOC value and Eloss 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 EU and energy loss, as well as obtain small driving force and high VOC for highly efficient OSCs.