Engineering performance of all-inorganic lead-free halide perovskites: A comprehensive review of innovations in photoluminescence, quantum yield, and stability

The relentless pursuit of stable and environmentally benign alternatives to lead halide perovskites has propelled lead-free variants to the forefront of optoelectronic materials research. However, their practical deployment is critically hindered by intrinsic limitations such as indirect or parity-forbidden bandgaps, low photoluminescence quantum yields (PLQYs), and insufficient environmental stability. Within this landscape, elemental doping, particularly with s-block cations (Li+, Na+, K+, Rb+, Mg2+, Ca2+, Sr2+, and Ba2+), has emerged as a uniquely versatile and powerful strategy for comprehensive performance enhancement. This comprehensive review critically examines the transformative role of s-block doping in revolutionizing the engineering performance of all-inorganic lead-free halide perovskites. We systematically elucidate the fundamental mechanisms through which these dopants modify local and global structure–property relationships. This includes breaking inversion symmetry to activate forbidden transitions, tailoring electron-phonon coupling to enhance self-trapped exciton emission, and effectively passivating ionic defects to suppress non-radiative recombination. The discussion navigates how strategic s-block incorporation tailors electronic band structures, dramatically enhances photoluminescence intensity and quantum yield (often elevating PLQYs from <1% to >90%), enables precise spectral tuning, and, most critically, confers unprecedented robustness against moisture, thermal stress, and photo-oxidation. By synthesizing the latest breakthroughs across diverse perovskite architectures, from 3D double perovskites to low-dimensional systems, this review establishes a coherent design paradigm for harnessing s-block elements as a universal toolbox for property optimization. We conclude by outlining emerging research avenues and future perspectives, including AI-accelerated discovery and advanced device integration, positioning s-block doping as a cornerstone strategy for realizing high-performance, industrially viable lead-free perovskite optoelectronics for applications in light-emitting diodes, scintillators, photovoltaics, and beyond.