Open AccessMolecular Design of Three-Dimensional Metal-Free A(NH4)X3 Perovskites for Photovoltaic Applications
Author(s) -
Jie Bie,
Dai-Bei Yang,
MingGang Ju,
Qiang Pan,
YuMeng You,
Wei Fa,
Xiao Cheng Zeng,
Shuang Chen
Publication year - 2021
Publication title -
jacs au
Language(s) - English
Resource type - Journals
ISSN - 2691-3704
DOI - 10.1021/jacsau.1c00014
Subject(s) - perovskite (structure) , chemistry , halogen , metal , transition metal , divalent , valence (chemistry) , inorganic chemistry , chemical physics , crystallography , catalysis , organic chemistry , alkyl
The intense research activities on the hybrid organic-inorganic perovskites (HOIPs) have led to the greatly improved light absorbers for solar cells with high power conversion efficiency (PCE). However, it is still challenging to find an alternative lead-free perovskite to replace the organohalide lead perovskites to achieve high PCE. This is because both previous experimental and theoretical investigations have shown that the Pb 2+ cations play a dominating role in contributing the desirable frontier electronic bands of the HOIPs for light absorbing. Recent advances in the chemical synthesis of three-dimensional (3D) metal-free perovskites, by replacing Pb 2+ with NH 4 + , have markedly enriched the family of multifunctionalized perovskites (Ye et al., Science2018, 361, 151-155). These metal-free perovskites possess the chemical formula of A(NH 4 )X 3 , where A is divalent organic cations and X denotes halogen atoms. Without involving transition-metal cations, the metal-free A(NH 4 )X 3 perovskites can entail notably different frontier electronic band features from those of the organohalide lead perovskites. Indeed, the valence and conduction bands of A(NH 4 )X 3 perovskites are mainly attributed by the halogen atoms and the divalent A 2+ organic cations, respectively. Importantly, a linear relationship between the bandgaps of A(NH 4 )X 3 perovskites and the lowest unoccupied molecular orbital energies of the A 2+ cations is identified, suggesting that bandgaps can be tailored via molecular design, especially through a chemical modification of the A 2+ cations. Our comprehensive computational study and molecular design predict a metal-free perovskite, namely, 6-ammonio-1-methyl-5-nitropyrimidin-1-ium-(NH 4 )I 3 , with a desirable bandgap of ∼1.74 eV and good optical absorption property, both being important requirements for photovoltaic applications. Moreover, the application of strain can further fine-tune the bandgap of this metal-free perovskite. Our proposed design principle not only offers chemical insights into the structure-property relationship of the multifunctional metal-free perovskites but also can facilitate the discovery of highly efficient alternative, lead-free perovskites for potential photovoltaic or optoelectronic applications.