Bandgap Science for Organic Solar Cells

Electronics

Masahiro Hiramoto¹  Masayuki Kubo¹  Yusuke Shinmura¹  Norihiro Ishiyama¹  Toshihiko Kaji¹  Kazuya Sakai³  Toshinobu Ohno² 

[1] Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan; E-Mails:;Osaka Municipal Technical Research Institute, 1-6-50 Morinomiya, Joto-ku, Osaka 536-8553, Japan; E-Mail:;Graduate School of Engineering, Osaka University, Yamadaoka, Suita, Osaka 565-0871, Japan; E-Mail:

关键词: organic solar cell;    doping;    bandgap science;    seven-nines purification;    phase-separation;    pn-control;    co-deposited film;    Kelvin band mapping;    carrier concentration;    ionization efficiency;    built-in potential design;    pn-homojunction;    metal/organic ohmic junction;    organic/organic ohmic homojunction;    tandem cell;   

DOI  :  10.3390/electronics3020351

来源: mdpi

【 摘 要 】

The concept of bandgap science of organic semiconductor films for use in photovoltaic cells, namely, high-purification, pn-control by doping, and design of the built-in potential based on precisely-evaluated doping parameters, is summarized. The principle characteristics of organic solar cells, namely, the exciton, donor (D)/acceptor (A) sensitization, and p-i-n cells containing co-deposited and D/A molecular blended i-interlayers, are explained. ‘Seven-nines’ (7N) purification, together with phase-separation/cystallization induced by co-evaporant 3^rd molecules allowed us to fabricate 5.3% efficient cells based on 1 µm-thick fullerene:phthalocyanine (C₆₀:H₂Pc) co-deposited films. pn-control techniques enabled by impurity doping for both single and co-deposited films were established. The carrier concentrations created by doping were determined by the Kelvin band mapping technique. The relatively high ionization efficiency of 10% for doped organic semiconductors can be explained by the formation of charge transfer (CT)-complexes between the dopants and the organic semiconductor molecules. A series of fundamental junctions, such as Schottky junctions, pn-homojunctions, p⁺, n⁺-organic/metal ohmic junctions, and n⁺-organic/p⁺-organic ohmic homojunctions, were fabricated in both single and co-deposited organic semiconductor films by impurity doping alone. A tandem cell showing 2.4% efficiency was fabricated in which the built-in electric field was designed by manipulating the doping.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.