Dependence of various oxide interfacial layers on the performance of P3HT:PCBM-based inverted organic solar cells

The development of organic solar cells (OSCs) during the past decade makes an excellent path for future photovoltaic technology, as it is accessible to all people owing to a simple and cost-effective fabrication process. Here we report the fabrication of inverted OSCs with various oxide interfacial layers (ZnO, SnO2). ZnO and SnO2 thin films were grown by spin-coating technique and it is used as an electron transport layer (ETL) in inverted OSCs. ZnO thin films with pure hexagonal wurtzite structure were obtained for the films annealed at 300°C. The bandgap of ZnO thin films calculated from the Tauc plot was found to be 3.27 eV. The optimum annealing temperature for the cubic-structured SnO2 thin films by spin-coating technique was 200°C. The inverted OSCs fabricated in ambient air conditions with ZnO as ETL showed a power conversion efficiency of 1.59%. The fabricated cell was then compared with inverted OSCs having SnO2 as the ETL and with conventional OSCs. The stability, efficiency and other performance parameters of the fabricated devices were calculated. The result indicates that inverted OSCs have significant improvement in stability compared to conventional OSCs. Also, inverted OSCs with ZnO exhibited higher efficiency and stability than OSCs fabricated with SnO2 as an ETL.