Significantly improved photovoltaic performance in polymer bulk heterojunction solar cells with graphene oxide/PEDOT: PSS double decked hole transport layer

This work demonstrates the high performance graphene oxide (GO)/PEDOT: PSS doubled decked hole transport layer (HTL) in the PCDTBT: PC71BM based bulk heterojunction organic photovoltaic device. The devices were tested on merits of their power conversion efficiency (PCE), reproducibility, stability and further compared with the devices with individual GO or PEDOT: PSS HTLs. Solar cells employing GO/PEDOT: PSS HTL yielded a PCE of 4.28% as compared to either of individual GO or PEDOT: PSS HTLs where they demonstrated PCEs of 2.77 and 3.57%, respectively. In case of single GO HTL, an inhomogeneous coating of ITO caused the poor performance whereas PEDOT: PSS is known to be hygroscopic and acidic which upon direct contact with ITO reduced the device performance. The improvement in the photovoltaic performance is mainly ascribed to the increased charge carriers mobility, short circuit current, open circuit voltage, fill factor, and decreased series resistance. The well matched work function of GO and PEDOT: PSS is likely to facilitate the charge transportation and an overall reduction in the series resistance. Moreover, GO could effectively block the electrons due to its large band-gap of similar to 3.6 eV, leading to an increased shunt resistance. In addition, we also observed the improvement in the reproducibility and stability.