Galle Marco H J J, Li Jun, Frantsuzov Pavel A, Basché Thomas, Scheblykin Ivan G
Department of Chemistry, Johannes Gutenberg-University, Duesbergweg 10-14, 55128, Mainz, Germany.
Chemical Physics and NanoLund, Lund University, Box 124, Lund, 22100, Sweden.
Adv Sci (Weinh). 2022 Dec 1;10(1):e2204393. doi: 10.1002/advs.202204393.
The photoluminescence (PL) of metal halide perovskites can recover after light or current-induced degradation. This self-healing ability is tested by acting mechanically on MAPbI polycrystalline microcrystals by an atomic force microscope tip (applying force, scratching, and cutting) while monitoring the PL. Although strain and crystal damage induce strong PL quenching, the initial balance between radiative and nonradiative processes in the microcrystals is restored within a few minutes. The stepwise quenching-recovery cycles induced by the mechanical action is interpreted as a modulation of the PL blinking behavior. This study proposes that the dynamic equilibrium between active and inactive states of the metastable nonradiative recombination centers causing blinking is perturbed by strain. Reversible stochastic transformation of several nonradiative centers per microcrystal under application/release of the local stress can lead to the observed PL quenching and recovery. Fitting the experimental PL trajectories by a phenomenological model based on viscoelasticity provides a characteristic time of strain relaxation in MAPbI on the order of 10-100 s. The key role of metastable defect states in nonradiative losses and in the self-healing properties of perovskites is suggested.
金属卤化物钙钛矿的光致发光（PL）在光或电流诱导降解后可以恢复。通过用原子力显微镜尖端对MAPbI多晶微晶施加机械作用（施加力、划痕和切割）并监测PL来测试这种自愈能力。尽管应变和晶体损伤会导致强烈的PL猝灭，但微晶中辐射和非辐射过程之间的初始平衡会在几分钟内恢复。机械作用引起的逐步猝灭-恢复循环被解释为PL闪烁行为的调制。该研究提出，导致闪烁的亚稳态非辐射复合中心的活跃态和非活跃态之间的动态平衡受到应变的干扰。在施加/释放局部应力的情况下，每个微晶中几个非辐射中心的可逆随机转变会导致观察到的PL猝灭和恢复。用基于粘弹性的现象学模型拟合实验PL轨迹，可以得到MAPbI中应变弛豫的特征时间，约为10-100秒。这表明了亚稳态缺陷态在钙钛矿的非辐射损失和自愈特性中的关键作用。
