Tunable Wide‐Bandgap Monohalide Perovskites

Abstract

Herein the mechanochemical synthesis of inorganic as well as hybrid organic–inorganic monohalide perovskites with tunable bandgaps is reported. It is shown that the bandgap bowing known for iodide mixed Sn–Pb perovskites is also present in the pure bromide analogous. This results in technologically very interesting materials with bandgaps in the range of 1.7–1.9 eV. Similar bandgap perovskites are typically achieved by mixing two halides that are prone to segregate over time. This limits the achievable open circuit voltage. For monohalide perovskites this problem is eliminated, making these materials especially promising wide bandgap absorbers for tandem solar cells.

Recent Advances and Perspectives on Powder‐Based Halide Perovskite Film Processing

“…[ 72 ] The applicability of single source vapor deposition to also complex halide perovskites such as Yb 3+ :CsPb(Cl 1‐x Br x ) 3 or highly alloyed (FA 0.81 MA 0.14 Cs 0.05 )Pb(Cl 0.02 Br 0.14 I 0.84 ) 3 was then demonstrated by Crane et al., [ 73 ] who also obtained very good film coverage on textured surfaces (Figure 4b). Within the past year, the perovskite powder‐based SSVD film processing was also shown for other stoichiometries, with mixtures in the B‐position, e.g., CsSn 0.3 Pb 0.7 Br 3 or Cs 3 Cu 2 I 5 , [ 37,74 ] as well as the fabrication of layers with a relatively high thickness of 890 nm (Figure 4c). However, the latter were not phase‐pure in contrast to thinner layers (250 nm), as evident from XRD measurements.…”

“…Heating up the perovskite powder sufficiently quick is a crucial aspect of SSVD, in order to minimize initial deviations in the evaporation rates of the individual constituents and to prevent material degradation, especially when organic cations are involved. [67,74] To address this issue, Kiyek et al recently initiated the evaporation process of perovskite powder not by applying an electric current, but by means of intense short laser pulses on a perovskite pellet (pulsed laser deposition: PLD), the latter being produced by pressing of mechanochemically synthesized perovskite source powder. [75] Using this pulsed laser deposition approach, compact CsSnI 3 thin films in the relevant black orthorhombic phase could be obtained, also in different thicknesses ( Figure 4d).…”

“…However, the latter were not phase‐pure in contrast to thinner layers (250 nm), as evident from XRD measurements. [ 74 ] It was assumed that an increase in the heating times of the perovskite powder due to the higher powder quantity was responsible for the film differences. Heating up the perovskite powder sufficiently quick is a crucial aspect of SSVD, in order to minimize initial deviations in the evaporation rates of the individual constituents and to prevent material degradation, especially when organic cations are involved.…”

“…Heating up the perovskite powder sufficiently quick is a crucial aspect of SSVD, in order to minimize initial deviations in the evaporation rates of the individual constituents and to prevent material degradation, especially when organic cations are involved. [ 67,74 ]…”

“…c) Reproduced with permission. [ 74 ] Copyright 2020, Wiley‐VCH. d) Reproduced under the terms of the CC‐BY 4.0 license.…”