A green and facile synthesis of lead-free hybrid organic-inorganic bismuth halides quantum dots for nanophotonics applications

There has been an urgent need to eliminate toxic lead from the popular halide perovskite for various photonics and optoelectronics applications. This is added by the use of dangerous and environment unfriendly chemical during the wet synthesis route. Herein we demonstrate the synthesis of lead-free halide perovskite – (PhA)BiI4 (phenylammonium tetraiodobismates) and PhABiBr4 (phenylammonium tetrabromobismates) quantum dots (QDs) in room ambient environment using eco-friendly solvent - Ethanol. FESEM-EDX analysis of PhABiI4 and PhABiBr4 confirm the 1:4 atomic ratio of Bi:I and Bi:Br. As revealed by HRTEM, the as-prepared PhABiI4 indicate the formation of QDs with sizes smaller than 10 nm. Similar morphology was observed for PhABiBr4 QDs, but smaller in size compared to PhABiI4. High optical transparency was observed, and optical bandgap was measured for both PhABiI4 and PhABiBr4 QDs at 2.25 eV for and 3.07 eV, respectively. Chromaticity studies under 365 nm irradiation reveal a bright cyan emission for the PhABiI4 and bright blue emission for the PhABiBr4 QDs. Large magnitude of nonlinear optical susceptibility, |χ(3)| were calculated in the order of 10−6 esu. The green and facile synthesis approach reported here represents an alternate avenue for the new applications of Bi-based perovskite particularly towards the next-generation nanophotonics technologies.