A relatively wide-bandgap and air-stable donor polymer for fabrication of efficient semitransparent and tandem organic photovoltaics

Significance Organic semiconductors are promising candidates for fabrication of semitransparent and tandem solar cells due to their low-cost processing, light weight, and solution processability. Here, we synthesize a donor copolymer (poly{[2,7-(5,5-didecyl-5H-1,8-dithia-as-indacenone)]-alt-[5,5-(5′,6′-dioctyloxy-4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]} [PDTIDTBT]) with relatively large bandgap and good stability. We show a stable and efficient semitransparent solar cell using graphene as electrode and achieve a power conversion efficiency (PCE) of 4.75% with average visible transmittance of 55%. We also demonstrate the application of the PDTIDTBT donor for tandem solar cell with PCE of up to 8.83% and long-term stability.