Large-Area Nanocrystalline Caesium Lead Chloride Thin Films: A Focus on the Exciton Recombination Dynamics.

Naomi Falsini,Nicola Calisi,Francesco Biccari,Chiara Barri,Paolo Scardi,Giammarco Roini,Monica Bollani,Andrea Ristori,Stefano Caporali,Anna Vinattieri

doi:10.3390/nano11020434

Abstract

Caesium lead halide perovskites were recently demonstrated to be a relevant class of semiconductors for photonics and optoelectronics. Unlike CsPbBr3 and CsPbI3, the realization of high-quality thin films of CsPbCl3, particularly interesting for highly efficient white LEDs when coupled to converting phosphors, is still a very demanding task. In this work we report the first successful deposition of nanocrystalline CsPbCl3 thin films (70–150 nm) by radio frequency magnetron sputtering on large-area substrates. We present a detailed investigation of the optical properties by high resolution photoluminescence (PL) spectroscopy, resolved in time and space in the range 10–300 K, providing quantitative information concerning carriers and excitons recombination dynamics. The PL is characterized by a limited inhomogeneous broadening (~15 meV at 10 K) and its origin is discussed from detailed analysis with investigations at the micro-scale. The samples, obtained without any post-growth treatment, show a homogeneous PL emission in spectrum and intensity on large sample areas (several cm2). Temperature dependent and time-resolved PL spectra elucidate the role of carrier trapping in determining the PL quenching up to room temperature. Our results open the route for the realization of large-area inorganic halide perovskite films for photonic and optoelectronic devices.

Highlights

Our results demonstrate the macroscopic homogeneity of the CsPbCl3 thin films on large sample areas, which is hardly achievable, especially with a single step deposition, without the addition of specific chemicals and without post-growth treatments
Several thin films of CsPbCl3 were deposited by radio frequency (RF) magnetron sputtering onto two properly cleaned different substrates: soda lime glass (SLG) and amorphous quartz slides
The samples investigated in this work are listed in Table 1: CsPbCl3 films of different thickness (70 and 150 nm) were realized on SLG and amorphous quartz substrates

Summary

Introduction

Caesium lead halide perovskites, described by the formula CsPbX3 (X = Cl, Br, I), are excellent active materials for coherent and incoherent light sources, sensors and innovative solar cells [3,4,5]. Their relevant electronic and optical properties (direct band gap, fine gap tunability by changing the halogen and alloying, high carrier mobility, defect tolerance, etc.) and, in particular, their higher thermal and chemical stability with respect. Among these fully inorganic perovskites, CsPbCl3 (band gap about 3.1 eV at room temperature [9])

Methods

Results

Conclusion