Tuning the optical properties of metal halide perovskitenanocrystals by shape engineering.

Metal halide perovskites nanocrystals(MHPN), owing to their unique and outstanding photophysical properties, have recently envisioned as promising active materials for wide range of photovoltaic and optoelectronic nanoscale device applications. Several degrees of freedom have been utilized to improve their photophysical properties with increased devise efficiency. Herein, we report the design strategy of shape engineering of CsPbBr3 nanocrystals (NCs) as a new degree of freedom for the first time to tune their photophysical properties. We demonstrate a remarkably contrasting behavior of dynamic Burstein-Moss effect (BME) and reduced many-particle Auger recombination when the shape of CsPbBr3 NCs optimized from usual 6 faceted cube to 12 faceted rhombic dodecahedron and 26 faceted rhombicuboctahedron. The BME is observed in the cubic and rhombic-dodecahedrons NCs with shift 26 and 20 meV respectively, and no shift in rhombicuboctahedron. It is observed that second-order decay is the major channel for carrier recombination with the rate of 3.68×10−10, 3.65×10−10 and 2.03×10−10 cm3 s−1 in cubic, rhombicdodecahedrons and rhombicuboctahedron. Furthermore, we reveal a manyfold reduction in gain threshold of amplified spontaneous emission (ASE) in the shape engineered NCs. These results offer critical insights into intrinsic photophysics in MHPN with direct implications for photovoltaic and optoelectronic applications by engineering shape of NCs. [ABSTRACT FROM AUTHOR]