Next Article in Journal
SmartStep: A Fully Integrated, Low-Power Insole Monitor
Next Article in Special Issue
Bio-Organic Electronics—Overview and Prospects for the Future
Previous Article in Journal
Footwear and Wrist Communication Links using 2.4 GHz and UWB Antennas
Previous Article in Special Issue
Strong Coupling between Plasmons and Organic Semiconductors
Article Menu

Export Article

Open AccessReview
Electronics 2014, 3(2), 351-380; doi:10.3390/electronics3020351

Bandgap Science for Organic Solar Cells

1
Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan
2
JST, CREST, 5, Sanbancho, Chiyoda-ku, Tokyo 102-0075, Japan
3
Graduate School of Engineering, Osaka University, Yamadaoka, Suita, Osaka 565-0871, Japan
4
Osaka Municipal Technical Research Institute, 1-6-50 Morinomiya, Joto-ku, Osaka 536-8553, Japan
5
Department of Production System Engineering, Toyohashi University of Technology, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan
*
Author to whom correspondence should be addressed.
Received: 18 February 2014 / Revised: 28 April 2014 / Accepted: 26 May 2014 / Published: 11 June 2014
(This article belongs to the Special Issue Organic Semiconductors)

Abstract

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 3rd 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.
Keywords: 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 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
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

Scifeed alert for new publications

Never miss any articles matching your research from any publisher
  • Get alerts for new papers matching your research
  • Find out the new papers from selected authors
  • Updated daily for 49'000+ journals and 6000+ publishers
  • Define your Scifeed now

SciFeed Share & Cite This Article

MDPI and ACS Style

Hiramoto, M.; Kubo, M.; Shinmura, Y.; Ishiyama, N.; Kaji, T.; Sakai, K.; Ohno, T.; Izaki, M. Bandgap Science for Organic Solar Cells. Electronics 2014, 3, 351-380.

Show more citation formats Show less citations formats

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Electronics EISSN 2079-9292 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top