Enhancing solar cell efficiency: lead-free double perovskite solar cells Cs2AgBiBr6 with magnesium-doped and Zn2SnO4 electron transport layer

The lead-free halide double perovskite solar cell (LFHDPs) \(C{s}_{2}AgBiB{r}_{6}\) has emerged as a compelling alternative to conventional lead-based perovskites (LBPs) owing to its notable advantages in chemical stability and non-toxicity. However, due to their large indirect bandgap (E_g), \(C{s}_{2}AgBiB{r}_{6}\) solar cells exhibit low efficiency (η). To address these challenges, this study explores the doping of \(C{s}_{2}AgBiB{r}_{6}\) double perovskite with Magnesium (Mg), resulting in a reduced E_g and improved η. Mg doping not only mitigates recombination losses but also enhances charge carrier mobility and stability. Additionally, the incorporation of a \(Z{n}_{2}Sn{O}_{4}\) (ZTO) electron transport layer (ETL) enhances η and stability by facilitating rapid charge injection and electron diffusion. Excellent optical and electrical characteristics of the ZTO-based ETL make it suitable for improving the η of charge collection and light harvesting in solar cells. Importantly, the \(C{s}_{2}A{g}_{0.95}M{g}_{0.05}BiB{r}_{6}\) solar cell exhibits enhanced performance, significantly, the fabricated solar cells exhibit improved performance. The measured values include an open circuit voltage (V_oc) of 0.9 V, a short circuit current density (J_sc) of 5.77 mA-cm⁻², a fill factor of 0.76, and a η of 3.98%. This study not only helps to overcome film formation issues but also validates stable \(C{s}_{2}A{g}_{0.95}M{g}_{0.05}BiB{r}_{6}\) as an efficient material for solar applications. Overall, our study improves solar technologies that are friendly to the environment.

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