Performance enhancement of inverted perovskite solar cells through interface engineering by TPD based bidentate self-assembled monolayers

Perovskite solar cells (PSCs) have recently appeared as a promising photovoltaic technology and attracted great interest in both photovoltaic industry and academic community. Numerous active researches related to the material processing and operational aspects of device fabrication are under progress since PSCs have a great potential for attaining higher performance compared to that of other solar cell technologies. In particular, interfacial engineering is a crucial issue for obtaining high efficiency in solar cells where perovskite absorber layer is deposited between hole and electron transport layers. In inverted type architecture, PEDOT:PSS is used as both hole transport layer and surface modifier; but unfortunately, this material bears instability due to its acidic nature. Thus, self-assembled monolayers (SAMs) not only are considered as suitable alternative, but also their application is regarded as an efficient and cost effective method to modify electrode surface since it provides a robust and stable surface coverage. In this context, we have employed two novel N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) based SAM molecules to customize indium tin oxide (ITO) surface in inverted type PSCs. Furthermore, fine-tuning of spacer groups enables us to study device performance depending on molecular structure. This study proposes promising materials for anode interface engineering and provides a feasible approach for production of organic semiconductor based SAMs to achieve high performance PSCs.