Water-Based Synthesis of CsPbBr₃ Perovskite Nanocrystals Under Ambient Conditions

Metal halide perovskites (MHPs) have revolutionised photovoltaics and emerging optoelectronic technologies, offering performance that rivals or exceeds that of conventional materials. Their rapid rise has been driven by their exceptional properties, including tuneable band gaps, high absorption coefficients, long carrier diffusion lengths and high mobilities, all combined with relatively simple synthesis. However, current MHP production relies heavily on the use of toxic solvents, which pose significant environmental and health risks. In addition, these methods often require complex multicomponent solvent systems and thermal processing to achieve the desired material phases, further hindering scalability and sustainability. Overcoming these challenges is critical to the future development of MHP-based technologies. Here, we present a novel water-based solvent system and synthetic approach for the controlled preparation of MHP nanocrystals. Our method enables the synthesis, in ambient air and at room temperature, of size-controlled CsPbBr₃ perovskite nanocrystals (PNCs) with a photoluminescence quantum yield (PLQY) exceeding 60%. To demonstrate the light to current conversion ability of our PNCs a series of photoconductors were prepared, with the best performing devices achieving a specific detectivity (D*) of 1.2 x 10 ¹¹ Jones. Thus, this green, scalable, and low-cost approach offers a sustainable pathway for precise size and compositional control of MHP nanocrystals, opening new possibilities for environmentally friendly optoelectronic applications.