All-Inorganic Halide Perovskite Nanocrystals: Future Prospects and Challenges to Go Lead Free

All-inorganic halide perovskite (IHP) materials have shown superior stability but the performance is still a bottleneck for commercial applications. Hence, extensive attention is given to IHP-based photovoltaics, light-emitting diodes (LEDs), and photodetection applications to procure the advantage of stability without compromising the efficiencies. Plenty of reviews have been reported so far where emphasis is given to a particular aspect such as synthesis, stability, application, or toxicity. However, synthesis, stability, and performance are the key aspects for all three major optoelectronic applications. Hence, it is necessary to bring all the recent pioneering works together from three inter-related optoelectronic applications. The detailed discussions on their synthesis, device architecture, performances, and stability of three applications are helpful for better understanding of the challenges. The toxicity of Pb is another issue to solve, especially in the present scenario of environmental crisis. Herein, the performances of lead and lead-free IHP devices are presented in a comparative manner to outline the future prospects and narrow down the several challenges to shift toward a completely Pb-free regime. Apart from three mainstream applications, other promising applications are pointed out with a brief discussion on their future potentials.