In situ incorporation of laser ablated PbS nanoparticles in CH3NH3PbI3 films by spin-dip coating and the subsequent effects on the planar junction CdS/CH3NH3PbI3 solar cells

Abstract

This is the first report on in situ incorporation of lead sulfide (PbS) nanoparticles in methyl ammonium perovskite thin films (CH3NH3PbI3:PbS) by the two step spin-dip method and the successive effects on the photovoltaic properties of HTM free Glass/FTO/CdS/CH3NH3PbI3 planar junctions. PbS nanocolloids of different concentrations were prepared by pulsed laser ablation of PbS target in isopropanol. CH3NH3PbI3:PbS thin films were synthesized by two step process of dipping spin coated PbI2 thin films in a dissolution of CH3NH3I in isopropanol containing PbS nanocolloids. Analysis on the structure, composition, morphology and optoelectronic properties of CH3NH3PbI3:PbS films with varying PbS nanoparticle concentrations were done and the results were compared with that of pristine CH3NH3PbI3 films. The CH3NH3PbI3:PbS films were of higher crystallinity with improved photocurrent sensitivity. The thin films were incorporated to HTM free p-n junction solar cells using chemical bath deposited CdS as window layer. The champion cell, Glass/FTO/CdS/CH3NH3PbI3:PbS showed Voc of 0.9 V, the highest value ever reported for HTM free p-n junction solar cell. Also, the device yielded Jsc of 7.76 mA/cm2, FF of 0.4 and a power conversion efficiency of 2.9%. The stability studies for 40 days evidenced that the champion device maintained the open circuit voltage unchanged.