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Theoretical Study on Electronic Structure of Bathocuproine: Renormalization of the Band Gap in the Crystalline State and the Large Exciton Binding Energy
Author(s) -
Yanagisawa Susumu,
Hatada Shinnosuke,
Morikawa Yoshitada
Publication year - 2016
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.201500379
Subject(s) - chemistry , exciton , band gap , binding energy , density functional theory , organic solar cell , electronic structure , molecular physics , electronic band structure , absorption (acoustics) , condensed matter physics , atomic physics , computational chemistry , optics , physics , organic chemistry , polymer
Bathocuproine (BCP) is a promising organic material of a hole blocking layer in organic light‐emitting diodes or an electron buffer layer in organic photovoltaic cells. The nature of the unoccupied electronic states is a key characteristic of the material, which play vital roles in the electron transport. To elucidate the electronic properties of the molecular or crystalline BCP, we use the GW approximation for calculation of the crystalline band gap, and the long‐range corrected (LC) density functional theory (DFT) for the molecular optical absorption. It is found that the band gap of the crystalline BCP is 4.39 eV, in agreement with the recent low‐energy inverse photoemission spectroscopy measurement. The polarization energy is estimated to be 1.05 eV, demonstrating the large polarization effects induced by the electronic clouds sur‐ rounding the injected charge. The theoretical optical absorption energy is 3.68 eV, and the exciton binding energy is estimated to be 0.71 eV, implying the large binding in the eletron‐hole pair distributed around the small part of the molecular region.