Enhanced the efficiency of TMs (Co and Ag) doped lead based mixed halides perovskite solar cells through the conduction band gap engineering

Abstract

This study introduces a method for improving the stability and efficiency of CsPbIBr₂ perovskite solar cells (PSCs) by using transition metals (TMs) doping. This approach not only decreases the lead (Pb) content but also reduces the conduction band offset (CBO), which helps to effectively minimize recombination losses. The structural properties of pure and transition metal doped CsPbIBr₂ perovskite film are investigated by X-ray diffraction (XRD). The XRD confirmed the cubic structure with the increased crystallite size from 18.4 to 37.8 nm. The optical properties were analyzed through UV–vis spectroscopy. The calculated energy band gap (E_g) reduced from 2.24 to 2.14 eV. So, by the transition metal doping in perovskite film, the conduction band (CB) of the perovskite layer is shifted near the CB of the electron transport layer (ETL). As a result, the conduction band offset (CBO) value decreases and a maximum number of electrons are injected from the perovskite layer into the TiO₂ ETL. The refractive index (n) increase (2.610–2.651) with Ag⁺ doping and reduced extinction coefficient (K). The electrical properties investigated by the current density-voltage (J-V) measurements, which confirm improved open-circuit voltage (V_oc) and short-circuit current density (J_sc), resulting in higher efficiency (7.35 %) compared to pure perovskite device (6.48 %). The enhanced performance is attributed to reduced recombination losses of electron-hole pairs within the perovskite layer as confirmed by reduced recombination resistance in EIS measurement, showcasing the potential of Ag doping as compared to pure and Co-doped devices for optimizing perovskite solar cells.