Enhanced performance of Sb2S3 mesoscopic sensitized solar cells employing TiO2:Nb compact layer

Abstract

This paper reports on the enhancement of charge transport and recombination by niobium doped compact layers of TiO2 in a solar cell with Sb2S3 absorber layer by characterizing both thin films of TiO2:Nb and working solar cell devices with the layer stack FTO/cp-TiO2:Nb/mp-TiO2/Sb2S3/P3HT/MoOx/Ag. The electron transport layers of TiO2 doped with 0.14 and 0.27 at.% Nb were prepared by spin coating and have no structural change as determined from the analysis of GIXRD spectra. SEM images show thin pin hole free layers of the cp-TiO2:Nb on FTO crystals that are agglomerates of particles. Analysis of the current–voltage curves of the solar cells with Sb2S3 as the absorber material showed increased short-circuit current, fill factor and power conversion efficiency from 1.3 to 1.7%. The enhancement of the device performance is attributed to substitution of Ti ions with Nb ions in the TiO2 resulting in a change in the band alignment of the solar cells with Nb content. This results in increase in charge recombination resistance in the Sb2S3 layer as determined from the analysis of the impedance spectroscopy measurements.