Radiative Monomolecular Recombination Boosts Amplified Spontaneous Emission in HC(NH₂)₂SnI₃ Perovskite Films

Abstract

Hybrid metal-halide perovskites have potential as cost-effective gain media for laser technology because of their superior optoelectronic properties. Although lead-halide perovskites have been most widely studied to date, tin-based perovskites have been proposed as a less toxic alternative. In this Letter, we show that amplified spontaneous emission (ASE) in formamidinium tin triiodide (FASnI3) thin films is supported by an observed radiative monomolecular charge recombination pathway deriving from its unintentional doping. Such a radiative component will be active even at the lowest charge-carrier densities, opening a pathway for ultralow light-emission thresholds. Using time-resolved THz photoconductivity analysis, we further show that the material has an unprecedentedly high charge-carrier mobility of 22 cm2 V–1 s–1 favoring efficient transport. In addition, FASnI3 exhibits strong radiative bimolecular recombination and Auger rates that are over an order of magnitude lower than for lead-halide perovskites. In combination, these properties reveal that tin-halide perovskites are highly suited to light-emitting devices.

Sn‐Based Perovskite for Highly Sensitive Photodetectors

“…The perovskite film has a large average grain size (≈500 nm) and can densely cover the substrate with good uniformity, which is beneficial for charge transport in the PD. [35,36] Such high mobility further confirms the high quality of the film and is desirable for carrier transport in PDs. As shown in Figure 1d, the sample displayed a sharp PL peak and an absorbance edge at around 890 nm, indicating its direct bandgap of ≈1.4 eV.…”

Recent Progress in Metal Halide Perovskite Micro‐ and Nanolasers

“…Notably, Milot et al found a small Auger recombination rate constant (0.93 × 10 −29 cm 6 s −1 ) in tin‐based perovskite (FASnI 3 ). This value is an order of magnitude smaller than that reported for lead‐based perovskites (in Figure c) . Such small Auger rate will benefit the tin‐based perovskites for coherent light emission at relative high injected carrier density.…”

“…Copyright 2017, Nature Publishing Group. (c) Reproduced with permission . Copyright 2016, American Chemical Society.…”

“…The latest report on double lead‐free perovskite that exhibited efficient and stable white‐light emission, the white light emission via STEs that originated from the Jahn–Teller distortion of the AgCl 6 octahedron in the excited state . Hitherto, to our best knowledge, lead‐free based perovskite micro‐/nanolasers formed in naturally synthesized cavities have not been reported yet, instead the ASEs achieved only from CsSnBr x I 3– x films fabricated by vapor deposition or FASnI 3 thin films by spin‐coating . In the earlier work of Xing et al, CsSnI 3 thin films with 20% SnF 2 additions exhibited ultralow‐threshold (≈6 µJ cm −2 ) and large‐gain (200 cm −1 ) stimulated emission.…”

Lead‐Free Tin‐Based Perovskite Solar Cells: Strategies Toward High Performance

“…The recombination process in Sn‐based perovskites under illumination can be described using the following equation where n and p are the densities of photo‐generated electrons and holes, respectively, p 0 is the hole doping density, k 1 nr is the nonradiative monomolecular recombination rate constant, k 2 is the bimolecular recombination rate constant (in the order of 10 −10 –10 −9 cm 3 s −1 , see Table ), k 3 is the Auger recombination rate constant (in the order of 10 −30 cm 6 s −1 ), and k 1 = k 1 nr + k 2 p 0 is the total rate constant of monomolecular recombination. It is special for Sn‐based perovskites that monomolecular recombination has contributions not only from nonradiative, trap‐assisted monomolecular recombination ( k 1 nr n ) but also from the radiative, pseudo‐monomolecular recombination between photo‐generated electrons and dopant holes density ( k 2 p 0 n ) as p 0 is very high . The reported value of k 1 for Sn‐based polycrystalline films is in the order of 10 8 –10 9 s −1 (Table ), which is several orders of magnitude higher than the typical values for MAPbI 3 .…”