High Voc solution-processed organic solar cells containing silicon phthalocyanine as a non-fullerene electron acceptor

Abstract Silicon phthalocyanines (SiPcs) have been identified as a candidate material for synthetically facile non-fullerene electron acceptors (NFAs) in solution processed organic photovoltaic (OPV) devices. Here we continue to investigate the use of bis(tri-n-butylsilyl oxide) SiPc ((3BS)2-SiPc) as a NFA paired with poly (3-hexylthiophene) (P3HT) and for the first time with poly [(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo [1,2-b:4,5-b’]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo [1′,2′-c:4′,5′-c’]dithiophene-4,8-dione)] (PBDB-T). We show improved efficiency of P3HT/(3BS)2-SiPc devices using an inverted structure, achieving an average power conversion efficiency (PCE) of 3.6%, the highest reported for SiPc-based NFA devices. PBDB-T/(3BS)2-SiPc devices show an average PCE of 3.4% with an impressive open circuit voltage as high as 1.10 V arising from a minimal donor/acceptor energetic offset. Under reduced light intensity the (3BS)2-SiPc devices show higher relative PCE compared to reference phenyl-C61-butyric acid methyl ester (PC61BM) devices, suggesting the materials could perform well in indoor or diffuse light applications. These results show great promise for SiPc derivatives as electron acceptors, with the potential for further improvement with optimization of active layer morphology and device architecture.