Thickness controlled fabrication of sb2s3 planner structure for the enhancement of light harvesting and charge collection efficiency

Abstract

Utilization of semiconductors as a light absorbing material has recently been receiving much attention. Among the range of investigated semiconductors, antimony sulfide (Sb2S3) is appealing as a promising light absorber due to its suitable bandgap (1.5 - 1.7 eV), one dimensional crystal structure and non-toxic constituents. Among a number of methods available, spin coating is known as the simplest technique to fabricate Sb2S3 thin films. In this investigation, the thickness of the Sb2S3 light harvesting layer was optimized by varying the spin coating conditions. Different Sb2S3 photoanodes were fabricated on the TiO2 compact layer/FTO substrates by spinning the Sb2S3 precursor solution of antimony chloride and thiourea (2:3) in 2-methoxyethanol at 3000, 4000, 5000 and 6000 rpm for 30 s. The devices, fabricated with the configuration of FTO/compact TiO2/Sb2S3/P3HT/Ag, showed an increase of solar cell performance with an increase of the spinning rate of the Sb2S3 precursor solution up to 5000 rpm. The thickness of Sb2S3 film, which was fabricated at 5000 rpm was ~ 265 nm, showed the highest power conversion efficiency of 4.01% with 619.2 mV as open circuit voltage, 14.05 mA cm-2 as short circuit current and 46.1% as a fill factor. The IPCE measurements were in good agreement with the I-V performance of the devices. Generally, the morphology of the films has no significant changes with the spinning speed. However, the thicknesses of Sb2S3 films were decreased by increasing spinning speed, which was examined by UV-Vis absorption spectra of Sb2S3 films. Therefore, the thickness of Sb2S3 film should be one of the critical factors that highly affects the performance of Sb2S3 solar cell devices. Herein, the performance of the Sb2S3 based solar cell was improved upon changing the thickness of Sb2S3 film based on spinning speed.