Lead-Free and Stable Potassium Titanium Halide Perovskites: Synthesis, Characterization and Solar Cell Simulation

Abstract

Titanium based double perovskites have shown good optical properties along with remarkable stability, making them promising lead-free perovskites for optoelectronic applications. In this work, Potassium Titanium Halide (K2TiBr6, K2TiI6 and K2TiI2Br4) double perovskites are synthesized for the first time. Surface topology and chemical composition are studied. Photoluminescence characterization shows a peak in the UV region. The perovskites exhibit quasi bandgap with K2TiI6 having 1.62 eV direct bandgap, conducive for single junction solar cell fabrication. K2TiBr6 and K2TiI2Br4 have bandgaps 2.14 eV and 2.44 eV, respectively, which is favorable for tandem solar cell application. The decomposition temperature of K2TiI6 is notable at 678 °C, bestowing it with stability in ambient atmosphere. Inherent to its optical properties, Solar Cell Capacitance Simulator-1D (SCAPS-1D) is used to simulate perovskite solar cell (PSC) with K2TiI6 as the absorber. Utilizing the absorption data from UV-Vis spectroscopy, these PSCs are designed to give maximum efficiency. Upon numerical optimization of perovskite layer thickness, we propose an efficient, practically realizable PSC with a power conversion efficiency of 4.382%. Besides, various electron and hole transport layers are investigated and the effect of their thickness on the PSC performance are studied.