Carboxylate-Containing Wide-Bandgap Polymers for High-Voltage Non-Fullerene Organic Solar Cells

Abstract

As one of the polymer modification strategies, carboxylate functionalization has proved effective in downshifting the energy levels and enhancing polymer crystallinity and aggregation. However, high-performance carboxylate-containing polymers are still limited for organic solar cells (OSCs), especially with open-circuit voltage (<i>V</i>_OC) above 1.0 V. Herein, we utilize two carboxylate-functionalized wide-band gap (WBG) donor polymers (<b>TTC-F</b> and <b>TTC-Cl</b>) to pair with two WBG electron acceptors (<b>BTA5</b> and <b>F-BTA5)</b> for high-voltage OSCs. Due to the deeper molecular energy levels, chlorinated polymer <b>TTC-Cl</b> shows higher <i>V</i>_OC than fluorinated polymer <b>TTC-F</b>. Furthermore, because of the stronger aggregation in the film, the <b>TTC-Cl</b>-based devices attain suppressed energetic disorders and trap-assisted recombination, decreasing voltage loss and <i>J</i>_SC loss. Finally, the <b>TTC-Cl</b>: <b>F-BTA5</b> blend achieves a higher <i>V</i>_OC of 1.17 V and an excellent PCE of 10.98%, one of the best results for high-voltage carboxylate-containing polymers. In addition, the <b>TTC-Cl</b>: <b>BTA5</b> combination demonstrates the highest <i>V</i>_OC of 1.25 V with an ultralow nonradiative energy loss of 0.17 eV. Our results indicate that the carboxylate-containing polymer donors have significant application potential for high-voltage OSCs due to reduced energy loss and improved charge transport and dissociation. Furthermore, the matched absorption spectra with the indoor light sources and low voltage loss promote these material combinations to construct high-performance indoor photovoltaics.