Defect states in hybrid solar cells consisting of Sb2S3 quantum dots and TiO2 nanoparticles

We have studied defect states in an organic-inorganic hybrid solar cell containing Sb2S3 quantum dots (QDs) and TiO2 nanoparticles (NPs) by using deep level transient spectroscopy (DLTS). An Au electrode was deposited as a Schottky contact on the sample, where the Sb2S3 QDs were distributed on the surface of TiO2 NPs by chemical synthesis. The activation energy and capture-cross section of an interface state between the Sb2S3 QDs and the TiO2 NPs were found to be about 0.78 eV and 2.21 × 10−9 cm−2, respectively. Also, the densities of this interface trap under a measurement voltage of −1 V were approximately 2.5 × 1017 cm−3. Based on these results, the interface trap was positioned around Ec − 1.03 eV below the conduction band edge of Sb2S3 QD. Thus, the external quantum efficiency of the solar cell was affected because of its role as a recombination center for carriers generated from Sb2S3 QDs.