Effect of halide ion replacement of RbGeX3 absorber material on the photovoltaic performance of pure inorganic perovskite solar cells

This work describes the optimization of photovoltaic parameters of the inorganic perovskite solar cell (PSC) with RbGeX 3 (X = I, Br, Cl) as the absorber layer, employing the DFT based absorption spectrum and band gap estimated with the help of WIEN2k software. For analysing the PSC using SCAPS 1D tool, IGZO and Cu 2 O are incorporated as the electron transporting layer and hole transporting layer respectively. Using Au as metal at the back electrode, the device configuration exhibits a peak PCE of 13.79% for RbGeI 3 based PSC when the SCAPS conventional absorption spectrum for RbGeI 3 is used for the study. However, when absorption spectrum obtained by DFT principles is employed for RbGeI 3 , device configuration exhibits a PCE of 6.49%. Our study shows that the absorption spectrum generated by DFT calculations is more reliable and accurate as it incorporates minute variations of absorption with quantum mechanical level of accuracy for different wavelengths of the incident light. When the halide ion I − of the perovskite structure, RbGeI 3 is replaced by Br − or Cl − , the device configurations exhibited PCE values of 10.09% and 3.69% respectively with SCAPS default absorption spectrum, mainly due to the increase in bandgap of the resulting perovskite structures, RbGeBr 3 and RbGeCl 3 while a PCE of 2.87% and 1.48% are achieved for device configurations with DFT absorption spectra of RbGeBr 3 and RbGeCl 3 respectively.