Spray-driven halide exchange in solid-state CsPbX
3 nanocrystal films.
NANOSCALE 2022;
14:13214-13226. [PMID:
36047914 DOI:
10.1039/d2nr03262g]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
CsPbI3 perovskite nanocrystals (NCs) are promising building blocks for photovoltaics and optoelectronics. However, they exhibit an essential drawback in the form of phase stability: α-phase, with a ∼1.80 eV bandgap, can easily experience a phase transition to a non-radiative orthorhombic δ-phase in an ambient environment. This leads to the need to carry out the CsPbI3-based device fabrication in an inert atmosphere, which is technologically inconvenient and expensive. One of the most successful approaches proposed to overcome this problem is synthesizing mixed halide CsPbBr3-xIx NCs to improve the stability of the α-phase perovskite structure. However, the formation of high-quality thin films of CsPbBr3-xIx NCs with high PLQY is challenging owing to the degradation of their optical properties after deposition on a substrate. This work presents spray coating to carry out a solid-state anion exchange in CsPbBr3 NCs thin films at ambient conditions with low-demanding reaction conditions. This constitutes a novel open-air and annealing-free technology to manufacture CsPbBr3-xIx NC thin films with high optical quality and record high photoluminescence quantum yields (PLQY) based on spray-driven halide (Br- to I-) anion exchange in a solid-state phase. Besides, tunable emission wavelengths between 520 and 670 nm can be obtained from CsPbBr3-xIx NC films using accurate tuning volumes of HI solution sprayed over the initial surface of CsPbBr3 film to provide the halide exchange. The optical quality of the halide-exchanged PNCs films remains practically identical to that of initial Br-containing layers, with a remarkable PLQY enhancement after anion exchange, from ∼61% for CsPbBr3 thin films emitting at 520 nm to ∼84% for mixed halide CsPbBr3-xIx film emitting at 640 nm. The huge potential of the system is confirmed by demonstrating a low-threshold amplified spontaneous emission.
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