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

Marco Anni,Yuhai Zhang,Arianna Cretì,Mauro Lomascolo,Maria Luisa De Giorgi

doi:10.3390/app10062148

Abstract

In this work, we present a detailed optical investigation of the effects of the environment on the photoluminescence (PL) spectra and the relaxation dynamics of pristine and aged CsPbBr3 nanocrystal (NC) thin films. We demonstrate that, contrary to previous results on similar NCs, the PL intensity of pristine NCs is higher when the sample is in wet air than in vacuum, due to the passivation of defects reducing the free exciton trapping and the bound excitons non-radiative relaxation. The aged NCs show a PL intensity increase in wet air nine times stronger than the pristine ones, due to an interplay between static and dynamic effects, increasing the number of emitting NCs and reducing the non-radiative recombination rate of free excitons. These results improve the understanding of the possible interactions between perovskite NCs and the environment, which could be relevant for the development of optical gas sensors exploiting perovskite NCs.

Highlights

Lead halide perovskites are receiving much attention as potentially interesting novel active materials for electronic, optoelectronic, and photonic devices, due to their unique combination of the active properties typical of semiconductors, wide degrees of freedom for their engineering, and possible realization and deposition with easy techniques.In particular, perovskite nanocrystals (NCs) are very interesting due to the possibility to engineer the optical properties by acting on the chemical composition [1], the size, the shape [2,3], and even the crystalline packing dimensionality within each NC [4]
Differently from what is observed in NCs grown by hot-injection, the PL intensity is higher in wet air
We show that the interaction with wet air (WA) results both in static and in dynamic effects, leading to a variation of the number of emitting NCs and of the exciton relaxation pathways

Summary

Introduction

Lead halide perovskites are receiving much attention as potentially interesting novel active materials for electronic, optoelectronic, and photonic devices, due to their unique combination of the active properties typical of semiconductors, wide degrees of freedom for their engineering, and possible realization and deposition with easy techniques. Perovskite nanocrystals (NCs) are very interesting due to the possibility to engineer the optical properties by acting on the chemical composition [1], the size, the shape [2,3], and even the crystalline packing dimensionality within each NC [4]. Despite the very rapid performance increase of perovskite-based solar cells [10], LEDs [11], and lasers [12], the applicative perspectives of these materials are currently limited by the lack of long term stability, strongly stimulating the research on the understanding of the processes leading to their degradation.

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