Preparation and characterization of regioregular poly(3-octylthiophene-2,5-diyl)/copper indium disenillide/titania heterojunction polymer solar cells

By optimizing the P3OT/CISe ratio, TiO2 content in the P3OT/CISe active layer, annealing temperature and time, this study investigated hybrid Al/Ca/P3OT:CISe:TiO2/PEDOT:PSS/ITO thin film solar cells with improved efficiency. Due to an increase in charge-carrier transport and a decrease of electron-hole recombination, it is possible to increase the efficiency of hybrid solar cells by adding TiO2 nanoparticles to the P3OT:CISe active film. Also, performance enhancement of the solar cells can occur with an increase of CISe content in P3OT as well as the addition of a PEDOT:PSS layer to the cell structure. The optimum TiO2 content in P3OT:CISe layer is 15 wt.%. The optimum annealing temperature and time are 125 °C and 30 min, respectively. The formation of large CISe and TiO2 aggregates that reduce charge mobility may cause the decrease of efficiency. The rough surface may effectively reduce the charge-transport distance and provide nanoscale phase separation that further enhances internal light scattering and light absorption. The best results for the open circuit voltages (Voc), short-circuit current density (Jsc), fill factor (FF), and efficiency (ηe) of Al/Ca/POCT15/PEDOT:PSS/ITO hybrid solar cells obtained at optimized conditions were Voc = 0.49, Jsc = 3.20, FF = 42.96, and ηe = 0.674, respectively.