Dataset Information

Strain-activated light-induced halide segregation in mixed-halide perovskite solids.

ABSTRACT: Light-induced halide segregation limits the bandgap tunability of mixed-halide perovskites for tandem photovoltaics. Here we report that light-induced halide segregation is strain-activated in MAPb(I_1-xBr_x)₃ with Br concentration below approximately 50%, while it is intrinsic for Br concentration over approximately 50%. Free-standing single crystals of CH₃NH₃Pb(I_0.65Br_0.35)₃ (35%Br) do not show halide segregation until uniaxial pressure is applied. Besides, 35%Br single crystals grown on lattice-mismatched substrates (e.g. single-crystal CaF₂) show inhomogeneous segregation due to heterogenous strain distribution. Through scanning probe microscopy, the above findings are successfully translated to polycrystalline thin films. For 35%Br thin films, halide segregation selectively occurs at grain boundaries due to localized strain at the boundaries; yet for 65%Br films, halide segregation occurs in the whole layer. We close by demonstrating that only the strain-activated halide segregation (35%Br/45%Br thin films) could be suppressed if the strain is properly released via additives (e.g. KI) or ideal substrates (e.g. SiO₂).

SUBMITTER: Zhao Y

PROVIDER: S-EPMC7730187 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Strain-activated light-induced halide segregation in mixed-halide perovskite solids.

Zhao Yicheng Y Miao Peng P Elia Jack J Hu Huiying H Wang Xiaoxia X Heumueller Thomas T Hou Yi Y Matt Gebhard J GJ Osvet Andres A Chen Yu-Ting YT Tarragó Mariona M de Ligny Dominique D Przybilla Thomas T Denninger Peter P Will Johannes J Zhang Jiyun J Tang Xiaofeng X Li Ning N He Chenglin C Pan Anlian A Meixner Alfred J AJ Spiecker Erdmann E Zhang Dai D Brabec Christoph J CJ

Nature communications 20201210 1

Light-induced halide segregation limits the bandgap tunability of mixed-halide perovskites for tandem photovoltaics. Here we report that light-induced halide segregation is strain-activated in MAPb(I1-xBrx)3 with Br concentration below approximately 50%, while it is intrinsic for Br concentration over approximately 50%. Free-standing single crystals of CH3NH3Pb(I0.65Br0.35)3 (35%Br) do not show halide segrega ...[more]

PMID: 33303755

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Project description:Despite the ideal performance demonstrated by mixed perovskite materials when used as active layers in photovoltaic devices, the factor which still hampers their use in real life remains the poor stability of their physico-chemical and functional properties when submitted to prolonged permanence in atmosphere, exposure to light and/or to moderately high temperature. We used high resolution photoelectron spectroscopy to compare the chemical state of triple cation, double halide Csx(FA0.83MA0.17)(1-x)Pb(I0.83Br0.17)3 perovskite thin films being freshly deposited or kept for one month in the dark or in the light in environmental conditions. Important deviations from the nominal composition were found in the samples aged in the dark, which, however, did not show evident signs of oxidation and basically preserved their own electronic structures. Ageing in the light determined a dramatic material deterioration with heavily perturbed chemical composition also due to reactions of the perovskite components with surface contaminants, promoted by the exposure to visible radiation. We also investigated the implications that 2D MXene flakes, recently identified as effective perovskite additive to improve solar cell efficiency, might have on the labile resilience of the material to external agents. Our results exclude any deleterious MXene influence on the perovskite stability and, actually, might evidence a mild stabilizing effect for the fresh samples, which, if doped, exhibited a lower deviation from the expected stoichiometry with respect to the undoped sample. The evolution of the undoped perovskites under thermal stress was studied by heating the samples in UHV while monitoring in real time, simultaneously, the behaviour of four representative material elements. Moreover, we could reveal the occurrence of fast changes induced in the fresh material by the photon beam as well as the enhanced decomposition triggered by the concurrent X-ray irradiation and thermal heating.

Dataset Information

Strain-activated light-induced halide segregation in mixed-halide perovskite solids.

Publications

Strain-activated light-induced halide segregation in mixed-halide perovskite solids.

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