Light Emission Properties of Thermally Evaporated CH3NH3PbBr3 Perovskite from Nano- to Macro-Scale: Role of Free and Localized Excitons

Abstract

Over the past decade, interest about metal halide perovskites has rapidly increased, as they can find wide application in optoelectronic devices. Nevertheless, although thermal evaporation is crucial for the development and engineering of such devices based on multilayer structures, the optical properties of thermally deposited perovskite layers (spontaneous and amplified spontaneous emission) have been poorly investigated. This paper is a study from a nano- to micro- and macro-scale about the role of light-emitting species (namely free carriers and excitons) and trap states in the spontaneous emission of thermally evaporated thin layers of CH3NH3PbBr3 perovskite after wet air UV light trap passivation. The map of light emission from grains, carried out by SNOM at the nanoscale and by micro-PL techniques, clearly indicates that free and localized excitons (EXs) are the dominant light-emitting species, the localized excitons being the dominant ones in the presence of crystallites. These species also have a key role in the amplified spontaneous emission (ASE) process: for higher excitation densities, the relative contribution of localized EXs basically remains constant, while a clear competition between ASE and free EXs spontaneous emission is present, which suggests that ASE is due to stimulated emission from the free EXs.

In Silico Investigation of the Impact of Hole-Transport Layers on the Performance of CH3NH3SnI3 Perovskite Photovoltaic Cells

“…At the same time, in spite of the excellent power conversion efficiencies [4][5][6], the technology still requires further improvement through reduction in costs, facilitation of the manufacturing steps and minimization of the environmental pollution associated with the production process [7][8][9]. In recent years, perovskite solar cells (PSC) based on organometallic lead halides have emerged as strong competitors to silicon in the photovoltaic market [10][11][12], as well as an efficient technology to complement the silicon photovoltaic devices in tandem architecture [13][14][15]. These materials boast high efficiency (about 25%) at a fraction of the silicon device thickness, as well as ease of fabrication, making them highly promising for future photovoltaic applications [16][17][18][19][20][21][22].…”