A new dialkylthio-substituted naphtho[2,3-c]thiophene-4,9-dione based polymer donor for high-performance polymer solar cells

Abstract

Rational molecular design towards high-performance photovoltaic materials with superior large-area capability is critical but still a challenge for the research field of polymer solar cells (PSCs). In this work, we design and synthesize a new dialkylthio-substituted conjugated polymer donor (namely PBN-S) to address this issue. PBN-S shows strong absorbance in the wavelength range of 500–700 nm and has a low-lying HOMO level of −5.48 eV, which matches that of the nonfullerene acceptor IT-4F. Optimized PSCs based on PBN-S:IT-4F demonstrate a high power conversion efficiency (PCE) of 13.10%, benefitting from the efficient charge separation, high and balanced charge mobility, ordered molecular packing and aggregation of the donor and acceptor materials in the active layer. In addition, the PCE of a PBN-S based semitransparent PSC reaches 9.83% with an average visible transmittance of 32%. What is more, remarkable PCEs of 10.21% and 10.69% were realized from spin-coated or blade-coated PSCs with an active area of 100 mm², respectively, indicating the great potential of PBN-S as a donor in high-performance large-area PSC application. More importantly, the PBN-S based devices show excellent shelf-life stability, retaining over 80% of their initial PCE after 100 days storage in a nitrogen-filled glove-box or in air. These results demonstrate the promising capability of PBN-S as a donor material for future PSC applications.