Investigating the effect of polythiocyanogen on morphology and stability of the perovskite layer and its application in the hole-transport material free perovskite solar cell

Abstract

Over the recent years, solid-state hybrid solar cells based on perovskite organ metal halides, i.e., CH3NH3PbX3 (X = I, Br, or Cl), have attracted considerable attention because of very rapid development and high conventional efficiency. At present, the most challenging part in perovskite solar cells is the high stability, which must be solved before putting them into the practical application. In this study, polythiocyanogen (SCN)n was used as an additive to improve the stability of the perovskite layer at the environmental condition. Polythiocyanogen have been used to replace iodide in CH3NH3PbI3, and the resulting perovskite films CH3NH3PbI3.(SCN)n are used as the active material in hole-transport material (HTM) free perovskite solar cells. Polythiocyanogen in the presence of iodine in the MAPbI3 exhibits semiconductor properties which can improve the performance of the perovskite solar cell. In this work, the CH3NH3PbI3.(SCN)n absorber layers with the various polythiocyanogen amount (0, 8, 16 and 24 mg/mL) and perovskite solar cells with the FTO/C-TiO2/Meso-TiO2/[CH3NH3PbI3.(SCN)n]/Au structure was fabricated. A one-step solution process was used for deposition of the CH3NH3PbI3.(SCN)n absorber layers. UV–vis spectra and XRD results reveal that polythiocyanogen could protect perovskite layer from degradation. Moreover, polythiocyanogen has photovoltaic properties and CH3NH3PbI3.(SCN)n perovskite solar cell shown better short-circuit current density (Jsc) and subsequently the higher power-conversion efficiency (PCE) as well. By adding a small amount of polythiocyanogen to the conventional layer of perovskite solar cell, the short-circuit current density JSC has increased from 5.26 to 11.75 mAcm-2, and the power-conversion efficiency PCE has increased from 2.95% to 6.27%.