Improved photovoltaic performance of bilayer small molecular solar cells via geometrical rearrangement of active materials

Abstract

Nowadays, non-fullerene electron transport material for the fabrication of organic photovoltaic devices has become one of extensive issue of research. But unfortunately, it has been observed that the replacements of the fullerene acceptors with non-fullerene acceptor materials typically led down the device efficiency. In this article, improvement in photovoltaic response of bilayer solar cells based on small molecular Zinc Phthalocyanine (ZnPc) and non-fullerene acceptor material (Perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA)) is reported via their geometrical rearrangement. The structural and optical property of ZnPc and PTCDA thin films were investigated using SEM, AFM, XRD and UV–vis absorption spectroscopy and their role on device performance is discussed in detail. It has been observed that the photovoltaic performance of the devices in PTCDA/ZnPc layer sequence exhibits 8 times higher value of JSC with almost double VOC that collectively shows 15 times higher value of the device efficiency as compared to the devices with ZnPc/PTCDA layer sequence. The results show that ZnPc and PTCDA exhibit complimentary absorption spectra but it would be efficient only if the materials are deposited in right sequence.