Improvement in performance of inverted organic solar cell by rare earth element lanthanum doped ZnO electron buffer layer

Abstract

In the past decade of robust innovation, the inverted organic solar cells (IOSCs) have been considered as a substitute photovoltaic technology with the potential to provide comparable power conversion efficiencies (PCEs) combined with low processing cost and ease in fabrication. The doping of metal oxides is an expedient technique for controlling the electronic band gap configurations of the electron buffer layer (EBL) in inverted organic solar cells for better performance. In addition, the sol-gel method is utilized for doping various functional materials as EBLs in IOSCs due to its cost effectiveness and uniform nanoscale film deposition. In this report, we analyzed the sol-gel-based ZnO films as EBLs for P3HT: PCBM based IOSCs. The ZnO film thickness was optimized and we studied the effect of lanthanum doping into the ZnO films by measuring the power conversion efficiency of the devices. In our study, lanthanum nitrate hexahydrate was selected as a potential lanthanum dopant. The IOSC device made with 1.57 atomic.%-lanthanum-doped ZnO (La-ZnO B) EBL showed a PCE of 4.34%, which is an increment of 12% as compared to the reference cell device containing a pure ZnO EBL. Therefore, we demonstrated that the lanthanum doping enhanced the interfacial electrical properties in terms of conductivity and carrier density.