Size-Dependent Photovoltaic Performance of CuInS₂ Quantum Dot-Sensitized Solar Cells

Abstract

The\noptical and electronic properties of quantum dots (QDs), which\nare drastically affected by their size, have a major impact on their\nperformance in devices such as solar cells. We now report the size-dependent\nsolar cell performance for CuInS₂ QDs capped with 1-dodecanethiol.\nPyramidal shaped CuInS₂ QDs with diameters between 2.9\nand 5.3 nm have been synthesized and assembled on mesoscopic TiO₂ films by electrophoretic deposition. Time-resolved emission\nand transient absorption spectroscopy measurements have ascertained\nthe role of internal and surface defects in determining the solar\ncell performance. An increase in power conversion efficiency (PCE)\nwas observed with the increasing size of QDs, with maximum values\nof 2.14 and 2.51% for 3.9 and 4.3 nm size particles, respectively.\nThe drop in PCE observed for larger QDs (5.3 nm) is attributed to\ndecreased charge separation following bandgap excitation. Because\nthe origin of photocurrent generation in CuInS₂ QDSC arises\nfrom the defect-dominated charge carriers, it offers the opportunity\nto further improve the efficiency by controlling these defect concentrations.