Room-temperature synthesis of lead-free copper(I)-antimony(III)-based double perovskite nanocrystals

Abstract

In the field of perovskite solar cells, explorations of new lead-free all-inorganic perovskite materials are of great interest to address the instability and toxicity issues of lead-based hybrid perovskites. Recently, copper-antimony-based double perovskite materials have been reported with ideal band gaps, which possess great potential as absorbers for photovoltaic applications. Here, we synthesize Cs2CuSbCl6 double perovskite nanocrystals (DPNCs) at ambient conditions by a facile and fast synthesis method, namely, a modified ligand-assisted reprecipitation method. We choose methanol as a solvent for precursor salts as it is less toxic and easily removed in contrast to widely used dimethylformamide. Our computational structure search shows that the Cs2CuSbCl6 structure containing alternating [CuCl6]5− and [SbCl6]3− octahedral units is a metastable phase that is 30 meV/atom higher in energy compared to the ground state structure with [CuCl3]2− and [SbCl6]3− polyhedra. However, this metastable Cs2CuSbCl6 double perovskite structure can be stabilized through solution-based nanocrystal synthesis. Using an anion-exchange method, Cs2CuSbBr6 DPNCs are obtained for the first time, featuring a narrow bandgap of 0.9 eV. Finally, taking advantage of the solution processability of DPNCs, smooth and dense Cs2CuSbCl6 and Cs2CuSbBr6 DPNC films are successfully fabricated.

Understanding the polaron behavior in Cs2CuSbCl6 halide double perovskite

“…As reported in the literature, the Fermi level of Cs 2 CuSbCl 6 is positioned approximately 1.20 eV above the valence band. 38 The calculated value of W H , obtained from Eqn (7), corresponds to 0.14 eV. Consequently, the value of E p is determined to be 0.28 eV, since E p = 2 W H .…”

Air-Stable Lead-Free Antimony-Based Perovskite Inspired Solar Cells and Modules

“…Over the past decade, lead-halide perovskite solar cells (PSCs) have made tremendous progress with power conversion efficiency (PCE) reaching 26.1%. , Although the matter is complex and must be analyzed from different angles (e.g., toxicity of elements and derivative compounds according to different tests, environmental footprint, life cycle analysis, which depends also on efficiency and performance etc. ), − and despite the excellent properties of Pb-based perovskites and low amounts found in PV cells and electronic products in which they will be integrated, the toxicity of heavy metal Pb may remain a concern for some of its practical applications. ,, Therefore, in recent years, scientists have initiated actions on developing potentially low-toxicity eco-friendly perovskite alternatives to produce the next-generation lead-free PSCs. − Major alternative classes to lead–halide perovskite comprise tin (Sn)-based − and germanium-based perovskites and derivatives, ,, double perovskites, , and bismuth (Bi)-based − and antimony (Sb)-based perovskite derivatives. − In this race to lead-free compounds, Sn-based perovskites have been more prominent with their PCE exceeding 14%. − Historically, these perovskites suffer from severe instability in the air; e.g., MASnI 3 undergoes chemical decomposition within seconds, due to the undesired oxidation of Sn 2+ into Sn 4+ . − Such poor stability together with unfortunate film morphology are the main reasons why fully laser-patterned (P1, P2, P3) working lead-free large-area PV modules had not been reported so far, since the large lasers used for module manufacturing are placed outside the glovebox and the laser scribing process often takes over tens of minutes or even hours …”