Effect of Band Bending and Energy Level Alignment at the Donor/Acceptor Interface on Open-Circuit Voltage in Organic Solar Cells

• Published in: The journal of physical chemistry letters Vol. 9; no. 11; pp. 2914 - 2918
• Main Authors: Izawa, Seiichiro, Shintaku, Naoto, Hiramoto, Masahiro
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 07.06.2018
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.8b01134

Open-circuit voltage (V OC) is a key parameter governing the power conversion efficiency of organic solar cells. We clarified the effect of band bending in organic semiconductor films on the V OC of phthalocyanine (H2Pc)/fullerene (C60) planar heterojunction (PHJ) OSCs. The V OC was significantly affected by the H2Pc layer thickness, varying from 0.20 V at 2 nm to 0.49 V at 100 nm thickness. The large V OC change is due to the band bending in the H2Pc layer, where the difference in H2Pc layer thickness led to significant changes in the degree of the vacuum-level shift in the C60 layer because of the Fermi level (E F) difference between the H2Pc and C60 layers. This result demonstrated that a new influential factor affecting the V OC is the position of the E F that is dependent on band bending in organic semiconductor films.