Abstract:
In this work, the effect of Sn, Cd doping on the structural, electronic and optical properties of novel trigonal KGeX3 (X=Br, I) perovskite is studied. The investigation is done by using both Density Functional Theory (DFT) and Solar Cell Capacitance Simulator (SCAPS-1D) simulation. The DFT is used to find out the effect of doping on crystal structure, band gap, electronic and optical properties. The SCAPS-1D is utilized to find out suitable electron transport layer (ETL), hole transport layer (HTL), optimum perovskite layer thickness and power conversion efficiency (PCE) of the solar device. In DFT analysis, it is observed that with the doping of Sn and Cd introduces new energy states within the band gap, thereby reducing the band gap. The optical absorbance, dielectric constant gets red shifted towards infrared region because of the reduction in band gap. All the Sn-doped perovskites are found to have direct band gap, meaning no extra phonon energy is required for electron transition, making them suitable for photovoltaic applications. The Sn doped perovskites also showed peak absorbance in the visible region of the spectrum. However, the Cd doped perovskite compositions are found to have indirect band gap. The combined DFT & SCAPS-1D simulation found out novel KGeI3, KSn0.67Ge0.33Br3, KSn0.33Ge0.67I3 and KCd0.33Ge0.67I3 inorganic perovskites compositions with optimum PCE % as 18.50 %, 13.93 %, 16.55 % and 18.11 % respectively. The band gap of these inorganic perovskites is found to be as 1.45, 1.69, 1.42 and 1.49 eV respectively, which are according to Shockley-Queisser limit, very suitable for photovoltaic application. The solar cell device architecture with KGeI3, KSn0.67Ge0.33Br3, KSn0.33Ge0.67I3 and KCd0.33Ge0.67I3 perovskites absorber layer is also found out. The CuI is found to be optimum HTL for all four inorganic perovskites. However, TiO2 is found to be optimum ETL for KGeI3, KCd0.33Ge0.67I3 perovskite and Indium gallium zinc oxide (IGZO) is found to be optimum ETL for KSn0.67Ge0.33Br3, KSn0.33Ge0.67I3 perovskite material. The Cu has been found to be optimum back metal contact for all four perovskites solar cell (PSC), which is cheaper than conventional back metal contacts. Overall, the inorganic K-based non-toxic perovskites simulated in this work is very promising for photovoltaic application in future.