Stable, Bromine-Free, Tetragonal Perovskites with 1.7 eV Bandgaps via A-Site Cation Substitution

Abstract

Metal halide perovskite absorbers with wide bandgaps (1.6−1.7 eV) that are suitable for tandem devices typically require high Br concentrations; this renders the material prone to halide segregation and degradation. Inorganic, bromine-free CsPbI3 has a wide bandgap of 1.7 eV and does not suffer from halide segregation; however, these active layers are not stable at room temperature. Here, we report a method to create stable tetragonal perovskites with a bandgap near 1.7 eV: we add small amounts of large A-site cations having ionic radii between 272 and 278 pmdimethylammonium (DMA) and guanidinium (Gua)into the crystal lattice. When we deploy perovskites using mixed Cs and these large organic cations, we achieve stable, wide bandgap perovskites with power conversion efficiencies of 15.2% and V OC of 1.19 V. This study extends materials selection for wide bandgap Cs-based perovskites.

Trojans That Flip the Black Phase: Impurity-Driven Stabilization and Spontaneous Strain Suppression in γ-CsPbI3 Perovskite

“…This particular aspect of APbI 3 compounds is what ultimately motivates the use of hybrid mixed cation organic−inorganic systems, i.e. those involving formamidinium (FA + ), methylammonium (MA + ), dimethylammonium (DMA + ), and guanidinium 36 (Gua + ).…”

Steric Engineering Enables Efficient and Photostable Wide‐Bandgap Perovskites for All‐Perovskite Tandem Solar Cells

“…[ 22 ] Recent studies have shown that larger A‐site cations such as dimethylammonium (DMA) and guanidinium were able to incorporate into the crystal lattice, so as to achieve wider bandgaps with identical or even lower Br contents. [ 23–27 ] A triple‐halide strategy by alloying a small amount of Cl was reported to reduce the Br content down to 15% in a 1.68 eV WBG perovskite, showing a suppressed light‐induced halide segregation. [ 28 ]…”

Regulating the phase stability and bandgap of quasi-2D Dion–Jacobson CsSnI3 perovskite via intercalating organic cations

“…All-inorganic lead halide perovskites (CsPbI 3 ) with great potential as next-generation solar energy absorbers have achieved their champion photovoltaic conversion efficiency (PCE) exceeding 17% 1,2 owing to their superior chemical stability, and outstanding electronic and photoelectric properties. 3–5 However, the commercial application of CsPbI 3 -based devices is severely impeded by the toxicity of the Pb element.…”