Premium
Complete Demonstration of the Valence Electronic Structure Inside a Practical Organic Solar Cell Probed by Low Energy Photoemission
Author(s) -
Nakayama Yasuo,
Nguyen Thanh Luan,
Ozawa Yusuke,
Machida Shin'ichi,
Sato Tomoya,
Tokairin Hiroshi,
Noguchi Yutaka,
Ishii Hisao
Publication year - 2014
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.201301354
Subject(s) - materials science , ultraviolet photoelectron spectroscopy , organic solar cell , x ray photoelectron spectroscopy , electronic structure , photoemission spectroscopy , optoelectronics , inverse photoemission spectroscopy , solar cell , angle resolved photoemission spectroscopy , band gap , copper phthalocyanine , ultraviolet , computational chemistry , chemistry , nuclear magnetic resonance , physics , composite material , polymer
The complete electronic structure inside a practical organic photovoltaic (OPV) device consisting of a trilayer structure of copper‐phthalocyanine (CuPc), fullerene (C 60 ), and bathocuproine (BCP) is demonstrated using low‐energy ultraviolet photoelectron spectroscopy (LE‐UPS) and photoelectron yield spectroscopy (PYS). The molecular orbital energy alignment and electrostatic potential distribution throughout the entire device is illustrated based on the LE‐UPS results. A favorable potential gradient to carry the photogenerated holes and electrons is manifested to be built spontaneously in the CuPc and BCP layers, respectively. Furthermore, the ultrahigh sensitivity measurements of LE‐UPS clearly unveil the distributions of faint density‐of‐states in the energy‐gap region in the organic films. Substantially barrierless contacts to both electrodes are fulfilled by the existence of these gap states. The electronic structure under simulated sunlight illumination is examined for the purpose of elucidating the electronic structures inside the working devices in the open‐circuit condition. These results indicate experimentally the electronic functionalities of each organic material, in particular of the BCP buffer layer, on the cell efficiency.