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

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.

Local Morphology Effects on the Photoluminescence Properties of Thin CsPbBr3 Nanocrystal Films

“…Moreover, very fast and strong improvements in the performance of perovskitebased optoelectronic and photonic devices, including LEDs [1,2], solar cells [3][4][5][6][7], optically pumped active waveguides and lasers [8][9][10][11][12], and optical sensors [13,14], have been obtained in the last few years.…”

Aging Effects on the Exciton Relaxation and Diffusion Processes in CsPbBr3 Nanocrystals

“…Interestingly, these experiments did not provide a unique and clear picture of the basic photophysics of these NCs. In particular, despite ample evidence that two different emitting states contribute to the PL spectra of NCs, [22,33,34] the temperature dependence of the spectral features (peak energy, linewidth, intensity, and relaxation dynamics) are always investigated for the entire spectra; [3,[34][35][36][37][38][39][40] thus, without a detailed investigation of the roles of the two emitting states and their natures, the possibility of ascribing the observed emission properties to the intrinsic properties of the investigated samples is lost.…”

“…Perovskite materials are of great interest in many fields of applications, such as photovoltaic, optoelectronic, and photonic, due to their electronic and optical properties, as well as the low different elements leading to perovskite degradation, water and moisture are particularly important and result in irreversible degradation due to decomposition of the active material [17,20] and reversible interactions leading to variations in the emission intensities and lifetimes. [18,[21][22][23] This is particularly important for NC films, which are characterized by larger surface/volume ratios relative to bulk polycrystalline thin films and higher surface defect densities.…”

Self‐Structural Healing of Encapsulated Perovskite Microcrystals for Improved Optical and Thermal Stability

“…[15][16][17][18][19][20] Moreover, it is wellaccepted that the stability of perovskites will be affected by light irradiation, humidity (aqueous vapor), and atmosphere (oxygen). [21][22][23] In order to obtain a stable device with high effi ciency, significant research efforts have been devoted to opti mize the property of perovskite materials, such as deposition techniques, composition regulating, as well as surface modi fication. For instance, using vaporphase conversion growth method for improved crystal quality of the material; or doping different ions into A, B, and X sites [24] for relieved crystal stress or increased chemical bonds strength.…”