Band gap engineered ternary semiconductor PbxCd1−xS: Nanoparticle‐sensitized solar cells with an efficiency of 8.5% under 1% sun—A combined theoretical and experimental study

Abstract

AbstractWe report the synthesis and photovoltaic properties of a ternary metal sulfide alloyed semiconductor PbxCd1−xS prepared by the two‐stage sequential ionic layer adsorption reaction. The synthesized PbxCd1−xS nanoparticles (NPs) retain the hexagonal structure of the CdS host with Pb substituting a fraction of the Cd atom (x = 0‐0.17). Band structures of PbxCd1−xS with various Pb contents x were calculated using the complementary density functional theory (DFT) method. Optical, quantum efficiency, cyclic voltammetry measurements, and band structure calculation revealed that the band gap of PbxCd1−xS decreased with increasing x, resulting in an increased optical absorption band from 500 to 720 nm (1.73‐2.44 eV) for x = 0 to 0.17. Solid‐state PbxCd1−xS semiconductor nanoparticle‐sensitized solar cells (NSSCs) were fabricated from the synthesized NPs using spiro‐OMeTAD as the hole‐transporting material. The best Pb0.05Cd0.95S cell yielded a power conversion efficiency (PCE) of 3.67%, a Voc of 0.70 V, and a fill factor (FF) of 62.8% under 1 sun. The PCE increased to 5.93% under a reduced light intensity of 0.1 sun and further increased to 8.48% under 0.01 sun. The external quantum efficiency (EQE) spectrum covers the spectral range of 300 to 730 nm with a maximal EQE of 82% at λ = 580 nm. The PCE over 8% can be categorized into a high‐efficiency NSSCs. In addition, the Voc of 0.70 V is a relatively high Voc among all NSSCs. The high PCE and Voc suggest that PbxCd1−xS has potential to be an efficient solar absorber.