Self‐Healing Ability of Perovskites Observed via Photoluminescence Response on Nanoscale Local Forces and Mechanical Damage

Abstract

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 3 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 3 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.

Correlation Clustering Imaging: A method for Functional Mapping of Semiconductor materials and photovoltaic devices in operando

“…(7)(8)(9)(10)(11)(12)(13)(14) In contrast, lightbased methods such as absorption, photoluminescence (PL) microscopy, and spectroscopy are non-invasive but suffer from limited resolution. (15)(16)(17)(18) Super-resolution microscopy techniques using luminescence have been impactful in fields such as biology and material sciences. (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29) However, due to the high chromophore density and the spatial mobility of emitting excited states in solid functional materials, most super -resolution methods fail to provide the structural insights they promise.…”

Photoluminescence Mapping over Laser Pulse Fluence and Repetition Rate as a Fingerprint of Charge and Defect Dynamics in Perovskites

“…The main challenges of working with perovskites are: i) poor sample storage stability, ii) poor reproducibility in sample fabrication, [10,11] and iii) evolution of the material under light irradiation, current flow, and electric field [12][13][14][15][16][17][18] and material self-healing. [19][20][21][22] Most of these difficulties, as well as advantages like, e.g., self-healing originate from low energy of defect formation, easiness of material recrystallization, [5] the ionic nature of the defect states and their metastability [22][23][24][25][26] due to very efficient ion migration in MHPs. [15,27,28] Unreliable performance of MHPs correlates with the extreme sensitivity on the specific details of the fabrication process, [10,[29][30][31][32] one of them being stoichiometries of precursor solutions.…”