High-efficiency Sb2S3-based hybrid solar cell at low light intensity: cell made of synthesized Cu and Se-doped Sb2S3

Abstract

Cu-doped (as p-doped) and Se-doped (as n-doped) Sb2S3 were synthesized from undoped Sb2S3 using a newly developed technique, simple colloidal synthesis method. X-ray diffraction measurements detected no peaks related to any of the Cu and Se compounds in Cu and Se-doped samples. Energy dispersive X-ray analysis, however, confirmed the presence of Cu and Se ions in the doped samples. Diffuse reflectance spectroscopy revealed the optical band gap energy changes because of doping effect, as reported for both the p-type and the n-type material. The valence-band X-ray photoelectron spectroscopy data showed a significant shift in the valence band to higher (Se-doped; +0.53eV) and a shift to lower (Cu-doped; -0.41eV) binding energy, respectively, when compared with the undoped sample. We report here on an inexpensive solar cell designed and made entirely of a synthesized material (indium tin oxide/p-doped Sb2S3+polyaniline (PANI)/amorphous/undoped Sb2S3+PANI/n-doped Sb2S3+PANI/PANI/electrolyte (0.5M KI+0.05M I-2)/Al). The cell has a high efficiency of 8% to 9% at a very low light intensity of only 5% sun, which makes it particularly suitable for indoor applications. As found, the cell performance at the intensity of 5% sun is governed by high shunt resistance (R-SH) only, which satisfies standard testing conditions. At higher light intensities (25% sun), however, the cell exhibits lower but not insignificant efficiency (around 2%) governed by both the series (R-S) and the R-SH. Minimal permeability in the UV region (up to 375nm) and its almost constant value in the visible and the NIR region at low light intensity of 5% sun could be the reasons for higher cell efficiency. Copyright (c) 2015 John Wiley and Sons, Ltd.