Exciton versus free carrier emission: Implications for photoluminescence efficiency and amplified spontaneous emission thresholds in quasi-2D and 3D perovskites

MATERIALS TODAY

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Article

Li, Yang^1,2  Allegro, Isabel¹  Kaiser, Milian¹  Malla, Aditya J.²  Richards, Bryce S.^1,2  Lemmer, Uli^1,2  Paetzold, Ulrich W.^1,2  Howard, Ian A.^1,2 

[1] Karlsruhe Inst Technol, Inst Microstruct Technol, Hermann Helmholtz Pl 1, D-76344 Eggenstein Leopoldshafen, Germany

[2] Karlsruhe Inst Technol, Light Technol Inst, Engesserstr 13, D-76131 Karlsruhe, Germany

关键词: Quasi-2D perovskite;    Light-emitting diodes;    Amplified spontaneous emission;    Exciton-exciton annihilation;   

DOI  :  10.1016/j.mattod.2021.05.002

来源: Elsevier

【 摘 要 】

Among perovskite semiconductors, quasi-two-dimensional (2D) materials are attractive for the pursuit of electrically driven lasing given their excellent performance in light-emitting diodes (LEDs) and their recent success in continuous-wave optically pumped lasing. We investigate the spontaneous photo-luminescence emission and amplified spontaneous emission (ASE) of a series of quasi-2D emitters, and their directly analogous 3D materials formed by removing the 2D organic spacer by annealing. Although the PL photoluminescence (PL) (at low optical excitation power) from quasi-2D films with high 2D spacer fractions can be much brighter than that from their 3D counterparts, the ASE thresholds of these quasi-2D materials tend to be higher. This counter-intuitive behavior is investigated through time-resolved photophysical studies, which reveal the emission in the high-spacer-content quasi-2D perovskite can be exclusively excitonic, and the exciton-exciton annihilation of quasi-2D perovskite starts to take over the exciton dynamics at a low exciton density (<10(16) cm(-3)). To lower ASE thresholds in quasi-2D materials it is necessary to increase the volume fraction of thick quantum wells, which we achieve by decreasing the spacer content or by utilizing 1-naphthylmethylamine (NMA) linkers. The increase of the volume fraction of thick quantum wells correlates with an increased contribution of free carrier recombination to the emission process of the quasi-2D materials. These results suggest that material development of quasi-2D materials for gain applications should target fast free charge carrier recombination rates by engineering the well thickness and size and not maximum photoluminescence quantum yields under low power excitation.

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