Polymer Donors with A New Electron-Deficient Unit for Efficient Organic Solar Cells

Abstract

Polymer donors, as a critical component of the active layer in organic solar cells (OSCs), necessitate the development of high-performance variants to further enhance efficiency. The exploration of novel electron-deficient building blocks plays a pivotal role in driving the sustainable advancement of high-performance polymer donors to date. In this study, we designed a new electron-deficient unit, dithienobenzobisthiadiazole (DTBBT), and synthesized its corresponding polymer materials (PD-1 and PD-2). Both polymers not only possess wide optical bandgaps exceeding 2.0 eV, but also show deep-lying highest occupied molecular orbital (HOMO) energy levels. When blended with a typical nonfullerene acceptor L8-BO, the PD-2:L8-BO-based binary devices achieved a satisfactory power conversion efficiency (PCE) of 16.34%, which could be attributed to their well-matched energy levels. Remarkably, PD-1-based polymer donors exhibit low non-radiative energy losses of only 0.174 eV in spite of its inferior PCE of 5.52%. Our results highlight DTBBT-based polymer donors as promising candidates for suppressing non-radiative energy losses in OSCs, offering new opportunities for further improving the device performance through molecular engineering.