New Method of Nickel Oxide as Hole Transport Layer and Characteristics of Nickel Oxide Based Perovskite Solar Cell

Abstract

NEW METHOD OF NICKEL OXIDE AS HOLE TRANSPORT LAYER AND CHARACTERISTICS OF NICKEL OXIDE BASED PEROVSKITE SOLAR CELL Loi Nguyen Old Dominion University, 2018 Director: Dr. Gon Namkoong For perovskite solar cells, poly (2,3-dihydrothieno-1, 4-dioxin)-poly (styrenesulfonate) (PEDOT:PSS) is a common hole transport layer. However, PEDOT:PSS has a lot of drawbacks, such as irregular quality from distributors, poor electron blocker, and hygroscopic nature. On the other hand, NiOx has been reported that it can provide good stability and carrier mobility. From literature, NiOx was used to replace PEDOT:PSS as a hole transport layer with positive results since it is transparent as a thin film and also possesses compatible work function in perovskite solar cell bandgap alignment. In depositing NiOx as a thin film, many approaches have been developed. However, those approaches required the use of acute toxic chemicals, lengthy processing time, complicated chemical requirement, and/ or expensive equipment. In order to obtain NiOx thin film as a hole transport layer, we have developed a facile method to obtain a thin film of NiOx by simply mixing NiOx powder and HCl solution. This process only needs less than 5 minutes of chemical mixing time and the precursor can be immediately spin-coated on top of substrate. In addition, the equipment needed to obtain thin film NiOx is a spin coater and a hot plate. With our quick, simple and inexpensive approach to get NiOx thin film for perovskite solar cells with inverted p-i-n structure, it is found that inverted perovskite solar cell with NiOx as a hole transport layer demonstrated higher open circuit voltage than perovskite solar cell fabricated with PEDOT:PSS, which enhanced solar cell power conversion efficiency. Our experiment has shown that NiOx thin film obtained by newly developed technique, exhibited promising material characteristics such as long lifetime decay. In our experiment, we also optimized the processing conditions of NiOx thin films to remove the light soaking effect caused by defects in NiOx layer. Hence, it is found that a quick, simple and inexpensive method enabled deposition of NiOx thin film as a promising hole transport layer for inverted p-i-n structure of perovskite solar cell.