Ultra-thin CdS buffer layer for efficient Sb2S3-sensitized TiO2 nanorod array solar cells using Sb-thiourea complex solution

In this paper, the compact and ultra-thin CdS thin films with different spin cycles are deposited on the TiO2 nanorod arrays via spin-coated-assisted successive ionic layer adsorption and reaction method using Cd(NO3)2 solution in methanol and the Na2S solution in methanol/water (v/v, 95/5), and the Sb2S3 prepared by pyrolysis using SbCl3-thiourea complex solution in DMF. In the Sb2S3-sensitized solar cells, the compact and ultra-thin CdS thin films with suitable band gap and higher electron mobility can suppress the charge recombination, the electrons of the TiO2 conduction band, and the holes of the spiro-OMeTAD valence band, and it can also transport photogenerated electrons rapidly from Sb2S3 to TiO2. The thickness and microstructure of the CdS buffer layers can be adjusted by spin cycles and the influence of the thickness and microstructure of the CdS buffer layers on the photovoltaic property of the corresponding solar cell was systematically investigated. The Sb2S3-sensitized solar cells with 5 layers CdS thin film achieved the best photovoltaic conversion efficiency (PCE) of 5.71% along with the open-circuit voltage (Voc) of 0.53 V, short-circuit photocurrent density (Jsc) of 18.20 mA cm−2, fill factor (FF) of 58.99%, and the average PCE of 5.59 ± 0.08% with the Voc of 0.53 ± 0.01 V, Jsc of 17.72 ± 0.43 mA cm−2, and FF of 59.05 ± 0.65%.