The Impact of Mg Dopant Concentration on the Performance of SnO₂ Electron Transport Layers in Perovskite Solar Cells

Recent experiments have highlighted the advantageous role of moderate magnesium (Mg) doping in tin dioxide (SnO₂) as an electron transport layer (ETL) in perovskite solar cells (PSCs), achieving high efficiencies driven by improved open-circuit voltage (V_OC).¹ The origin of this improvement is debated, attributed either to enhanced film quality or to changes in electronic structure from Mg doping. This study uses density functional theory (DFT) calculations to investigate the structural, electronic, and defect properties of SnO₂ with varying Mg doping levels.² Results indicate that low Mg content raises the conduction band minimum (CBM), enhancing V_OC, while high Mg concentrations result in interstitial Mg defects, decreasing V_OC and creating intra-gap states that reduce PSC performance. These findings offer an atomic-level understanding of Mg doping effects on SnO₂, guiding the design of ETL materials with tailored electronic properties for advanced solar cells. The study also provides a comprehensive computational analysis of Mg-doped SnO₂, from bulk properties to surface work functions, to explain the variations in V_OC observed experimentally.<br/><br/>1 L. Xiong, M. Qin, G. Yang, Y. Guo, H. Lei, Q. Liu, W. Ke, H. Tao, P. Qin, S. Li, H. Yu and G. Fang, J. Mater. Chem. A, 2016, 4, 8374–8383.<br/><br/>2 G. V. Sannino, A. Pecoraro, P. Maddalena, A. Bruno, P. D. Veneri, M. Pavone and A. B. Muñoz-García, Sustainable Energy Fuels, 2023, <b>7</b>, 4855–4863.