CH3NH3PbI3/CdS planar photovoltaic junction by spin-dip coating: Studies on the effects of PbI2 layer thickness and rapid thermal treatments

•CdS/CH3NH3PbI3 planar PV devices were synthesized and characterized.•The effects of rapid thermal processing of CH3NH3PbI3 and PbI2 precursor layer on the devices.•RTP resulted higher Voc of 0.62 V and Jsc of 5.2 mA/cm2.•Improvement in crystallinity of the perovskite films due to RTP.•Change in the preferential orientation of perovskite by RTP-PbI2 as precursor layer. Photovoltaic structures of Glass/FTO/CdS/CH3NH3PbI3 have been fabricated and the effects of rapid thermal processing (RTP) on these structures are investigated. First, CdS thin films were deposited by chemical bath deposition on which PbI2 by spin coating followed by 60 min dipping in 0.1 M CH3NH3I solution, varying PbI2 concentrations (0.6–1 M). Studies on the effects of RTP of the CH3NH3PbI3 films and the PbI2 precursor layers revealed an increase in the open-circuit voltage as well as the short curcuit current due to the improved crystallinity and the change in the preferential orientation of the perovskite growth leading to better charge transport. The samples were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, and scanning electron microscopy. The optical and electrical properties were also measured.The perovskite films formed exhibited tetragonal crystalline structure with uniform and compact morphology. The thin films were photoconductive and possessed a direct band gap of 1.5–1.6 eV. The XPS analysis showed the presence of the constituent elements and their chemical states. The photovoltaic parameters of the best cells were: Voc = 0.62 V, Jsc = 5.2 mA/cm2, FF = 0.43 and an efficiency of 1.2%. The present work span the scope of the hybrid perovskite mateirals in the conventional p-n heterojuntion solar cells free of any organic HTM layers.