High Performance Organic Photovoltaics with Transparent Oxide Interlayer

Abstract

Organic photovoltaics (OPVs) have remarkable attention due to their cost-effective, simple process and large area manufacturing as energy sources for printed and flexible electronics. In this talk, we demonstrate that inorganic interlayer can prominently improve the performance of inverted polymer solar cells with the mixture of [6,6]-phenyl C71-butyric acid methyl ester (PC70BM) and diverse donors, such as poly[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]-thiophenediyl(PTB7) and many more.One of the common technique to enhance the electrical and optical properties of inorganic thin film layer has been suggested with doping of various metals for oxide inorganic films, such as ZnO, TiO2 and other metal oxides. It was recently reported that metal doping of ZnO thin film such as Li, Al, or Ga is an effective way to modify the grain size and orientation of ZnO crystallites. It may predominantly be effective as the structural, optical and electrical properties enhancer. Here, we adopted various metal dopants to inverted OPVs in ZnO and TiO2 interlayers. The doped ZnO film with a number of dopants, thus, such as Al, Ga, In, Li and Cd, was prepared by sol-gel spin coating and the optimized doping concentration appeared for each dopant. As suggested as one of the most highly improved efficiency, In-doped ZnO (IZO) film with 6 at. % of In concentration was intercalated between the ITO electrode and the active layer. As a result, the power conversion efficiency approaches 9 % exceedingly. Moreover, the underlying mechanism was revealed as the suppressed absorption and facilitated electron extraction of inorganic interlayer with metal doping through the first principles calculations and finite difference time domain (FDTD) optical simulation.