Premium
Characterization of the Valence and Conduction Band Levels of n = 1 2D Perovskites: A Combined Experimental and Theoretical Investigation
Author(s) -
Silver Scott,
Yin Jun,
Li Hong,
Brédas JeanLuc,
Kahn Antoine
Publication year - 2018
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201703468
Subject(s) - perovskite (structure) , materials science , exciton , binding energy , valence (chemistry) , density functional theory , band gap , iodide , halide , electronic band structure , ionization energy , analytical chemistry (journal) , ionization , crystallography , condensed matter physics , atomic physics , inorganic chemistry , chemistry , computational chemistry , physics , ion , optoelectronics , organic chemistry , chromatography
This study presents a combined experimental and theoretical study of the electronic structure of two 2D metal halide perovskite films. Ultraviolet and inverse photoemission spectroscopies are performed on solution‐processed thin films of the n = 1 layered perovskite butylammonium lead iodide and bromide, BA 2 PbI 4 and BA 2 PbBr 4 , characterized by optical absorption and X‐ray diffraction, to determine their valence and conduction band densities of states, transport gaps, and exciton binding energies. The electron spectroscopy results are compared with the densities of states determined by density functional theory calculations. The remarkable agreement between experiment and calculation enables a detailed identification and analysis of the organic and inorganic contributions to the valence and conduction bands of these two hybrid perovskites. The electron affinity and ionization energies are found to be 3.1 and 5.8 eV for BA 2 PbI 4 , and 3.1 and 6.5 eV for BA 2 PbBr 4 . The exciton binding energies are estimated to be 260 and 300 meV for the two materials, respectively. The 2D lead iodide and bromide perovskites exhibit significantly less band dispersion and a larger density of states at the band edges than the 3D analogs. The effects of using various organic ligands are also discussed.