Compact-Type Quasi-2D Perovskite Based on Two Conventional 3D Perovskites.

Zhang, Haihua; Wu, Chuang; Xu, Wenbao; Fu, Hongbing · Nano Lett · 2023

basic_science · Level V

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Abstract

Quasi-2D perovskites are natural quantum well (QW) structures composed of insulating organic layers inserted between conducting [A<sub><i>n</i>-1</sub>Pb<sub><i>n</i></sub>X<sub>3<i>n</i>+1</sub>]<sup>2-</sup> slabs. The presence of the bulky organic layer improves the stability but meanwhile sacrifices carrier transport performance. By utilizing two A-site cations of formamidinium (FA<sup>+</sup>) and cesium (Cs<sup>+</sup>), we synthesize unique compact-type quasi-2D perovskites CsPbBr<sub>3</sub>@FABr. Instead of the bulky organic cations, the FA<sup>+</sup> cation was employed to work as interlayer "spacer", while the smaller Cs<sup>+</sup> cation was chosen to occupy perovskite cages. Transient absorption reveals an energy transfer from small-<i>n</i>-value QWs to large-<i>n</i>-value QWs, enabling a photoluminescence quantum yield (PLQY) of 36.1%. After further promoting the formation of middle-<i>n</i>-value QWs, the homogeneous QW distribution provides a complete energy cascade to access more efficient energy transfer, leading to significant PLQY raise to 70.1%. We break the shackles to report the first case of compact-type quasi-2D perovskites, providing new guidelines for designing high-performance perovskite materials for optoelectronic devices.