Lead-free double halide perovskite Cs ₃ BiBr ₆ with well-defined crystal structure and high thermal stability for optoelectronics

Halide perovskites have continued to rise as attractive light absorber materials, mainly driven by their potential wide applications in the fields of solar cells, photodetectors, lasers and others. However, Pb-containing perovskites are poisonous and could cause serious potential problems to our environment. Thus, there is a strong desire to develop lead-free perovskites as environmentally friendly alternatives. Here, we have shown a successful synthesis of a non-toxic single crystalline double-halide perovskite, Cs ₃ BiBr ₆ , and analysed its structural characteristics in detail. This perovskite represents a new structure in terms of double-halide perovskites. The crystal structure features isolated BiBr ₆ polyhedra forming a zero-dimensional halide perovskite. The bandgap of this compound is measured to be 2.55 eV. High thermal stability is also clearly shown in the Cs ₃ BiBr ₆ single crystal. A photodetector based on this compound is fabricated and tested, which exhibits an impressive detectivity of 0.8 × 10 ⁹ Jones and low dark current under 400 nm light illumination. Overall, our results show that the Cs ₃ BiBr ₆ perovskite as a lead-free perovskite has interesting structures and promising properties for optoelectronic devices.