Practical use of Ruddlesden–Popper (RP) metal halide perovskites for optoelectronics is still limited by their environmental and thermal degradation, and to address these challenges, mixed-cation engineering of the A-site, particularly through alkali cation incorporation, has emerged as an effective strategy by providing synergistic control over lattice strain and interlayer interactions. Building on this approach, we investigate the impact of cesium (Cs) incorporation in quasi-2D RP perovskites by studying their moisture resistance, thermal stability, optoelectronic performance, and activation energy analysis. At optimum Cs concentration (Cs10), as smaller inorganic cations into methylammonium (MA)-based (BA)2(MA)3Pb4I13 (n = 4), RP perovskites showed enhanced crystallinity, reduced interlayer spacing, and improved charge transport properties. UV–vis and PL spectroscopy confirmed a slight blue shift in the bandgap, while XRD confirmed structural integrity. Thermogravimetric analysis demonstrates that Cs10 perovskites possess superior thermal stability with reduced weight loss and higher decomposition onset compared to pristine samples. In addition, transient photocurrent measurements demonstrate superior daywise stability for Cs10 RP perovskites. Under 1 sun illumination, fabricated lateral photodetectors (FTO/perovskite (PSK)/FTO) revealed higher transient photocurrent density (∼105 μA/cm2) for optimized Cs10 RP perovskites compared to pristine RP perovskite (∼40 μA/cm2), along with an enhanced responsivity (1.05 vs 0.40 mA/W) and shorter response time (212 vs 932 ms). Subsequently, Cs10 devices subjected to temperature-dependent IV measurements under dark conditions for 213 K–403 K showed relatively lower dark current with exceptional thermal stability and no degradation up to 403 K (130 °C), indicating their reduced charge carrier recombination and trap stabilization compared to undoped samples, as further validated by Arrhenius plots analysis. These findings provide key insights into designing RP perovskite-based photodetectors with a wide operational temperature range.
Rahil et al. (Mon,) studied this question.