Reversible air-induced optical and electrical modulation of methylammonium lead bromide (MAPbBr3) single crystals

Abstract

The photoluminescence (PL) variations of organic-inorganic hybrid lead halide perovskites in different atmospheres are well documented, while the fundamental mechanism still lacks comprehensive understandings. This study reports the reversible optical and electrical properties of methylammonium lead bromide (MAPbBr3 or CH3NH3PbBr3) single crystals caused by air infiltration. With the change in the surrounding atmosphere from air to vacuum, the PL intensity of perovskite single crystals decreases, while the conductivity increases. By means of first-principles computational studies, the shallow trap states are considered as key elements in PL and conductivity changes. These results have important implications for the characterization and application of organic-inorganic hybrid lead halide perovskites in vacuum.

Divalent Anionic Doping in Perovskite Solar Cells for Enhanced Chemical Stability

“…Visually guided by dashed lines in Figure c, diffraction peaks of 10% w/w PbSe:MAPbI 3 shift towards smaller 2θ angles for (110), (112), (220), and (310) planes in comparsion with MAPbI 3 , and therefore indicates enlarged lattice constants as caused by intercalation of dopant atoms into the perovskite lattice. Such observation is in accordance with previous reports, where increased content of I − in MAPbI 3‐x Br x and insertion of water molecules in MAPbBr 3 systems result in diffraction peaks shifted to smaller 2θ angles. Although Se 2− ( r = 198 pm) has an ionic radius slightly smaller than I − ( r = 220 pm), it is still perfectly reasonable to result in an expanded perovskite lattice due to interstitial intercalation (instead of X‐site lattice points), and interstitial intercalation should leads to inefficient atomic packing, as in the cases of small alkali metal ion (Rb + , Li + , etc.)…”

Investigation of the Role of the Environment on the Photoluminescence and the Exciton Relaxation of CsPbBr3 Nanocrystals Thin Films

“…To understand the processes leading to the PL intensity dependence on the environment in Sample #F and the origin of the strongly different behavior observed in Sample #A, it is first useful to remind that the PL intensity increase observed in both samples is qualitatively similar to the one reported both for lead halide perovskites polycrystalline thin films [22][23][24][25] and single crystals [26,27]. In all these systems, the PL intensity increase in WA has been ascribed to oxygen or moisture induced passivation of halide vacancies, which reduces the non-radiative decay rate, thus increasing the PLQY and the PL lifetime.…”

“…The presence of PL enhancement in WA in our samples thus suggests that the co-precipitation growth method leads to the formation of NCs with a higher density of bromine vacancies on the surface with respect to NCs grown by hot-injection. It is also important to underline that the very high PLQY of the just deposited films and the relatively small PL intensity increase of Sample #F suggest a defect density much smaller than the one of bulk polycrystalline films and single crystals, typically showing much lower initial PLQY and much higher PL enhancement in WA [22][23][24][25][26][27]. We also underline that the observed small red-shift and the narrowing of the FE and BE bands are consistent with previous results on MAPbI 3 thin films [24], ascribed to defects passivation without irreversible degradation.…”

“…To date, it has been demonstrated that lead halide perovskites can be degraded by many factors such as temperature [13], light exposure [13][14][15][16][17], and interaction with oxygen and moisture [18][19][20][21]. Interestingly, despite the reports of material degradation due to its interaction with air, several experiments demonstrated that the interaction with oxygen and wet air can also improve the light emission and the device performances of bulk polycrystalline thin films [22][23][24][25] and single crystals [26,27]. This effect, typically reversible, is generally ascribed to the oxygen passivation of halide vacancies taking place at the air-perovskite interface, which decreases the excitation non-radiative decay rate, thus increasing the photoluminescence (PL) intensity and decreasing the PL decay rate [22][23][24][25][26][27].…”

Switching excitonic recombination and carrier trapping in cesium lead halide perovskites by air

“…Therefore, understanding the interaction between semiconductors and their environment is essential for the optimization of optoelectronic devices [18][19][20][21][22] . In the past several years, tremendous research efforts had been devoted to investigating the interaction between organic-inorganic hybrid halide perovskites and their environment, which resulted in a better fundamental understanding and significant improvement of device performances 15,18,19,[23][24][25][26][27][28] . However, up till now, it much less is known about how the atmospheric condition affects the ILHPs, which may partially account for the currently lagging device efficiency as compared with those made from the hybrid halide perovsktes 6,11,29 .…”