Experimental and theoretical analysis of doping methylammonium lead iodide perovskite thin films with barium and magnesium

We report on the study of barium (Ba) and magnesium (Mg)-doped methylammonium lead iodide (CH3NH3PbI3) deposited onto spin-coated titanium dioxide (TiO2) films, acting as the electron transport layer. Comprehensive characterizations of surface morphology, structural, elemental, and optical properties were carried out employing scanning electron microscopy, X-ray diffractometry, energy-dispersive X-ray spectrometry, and spectrophotometry techniques. In addition, first-principles density functional theory (DFT) calculations were performed to elucidate the electronic and optical characteristics of the doped CH3NH3PbI3 films. The results revealed that doping instigates the formation of evenly distributed, mesoporous grain-like clusters with crystalline structures. Specifics of the elemental composition, high absorbance, and band gap energy values were also discovered and are reported herein. Notably, the energy band gaps of the Ba and Mg-doped samples, CH3NH3Pb1-XBaXI3-2XCl2X and CH3NH3Pb1-XMgXI3-2XCl2X, were found to be 1.95 eV and 1.97 eV respectively, which are marginally higher than the 1.90 eV band gap of the pristine MAPbI(3). The experimental energy band gaps are in reasonable agreement with our DFT-derived band gaps of 1.76 eV, 1.92 eV, and 2.05 eV for the pristine, Ba-doped, and Mg-doped samples, respectively. Optical characterization further showed that the Ba and Mg doping reduces the photon transmittance of the materials while concurrently promoting the Pb electronic states deeper into the conduction band. Based on these observations, our findings suggest that the introduction of Ba and Mg into the pristine CH3NH3PbI3 perovskite significantly enhances its performance, making it a highly suitable material for perovskite solar cell applications.