Jump to main content
Jump to site search


The direct observation of electron backflow in an organic heterojunction formed by two n type materials

Abstract

Many physical processes such as exciton interfacial dissociation, exciton interfacial recombination, exciton-electron and exciton-hole interactions coexist at the interface of organic solar cells (OSC). In this study, the direction of free charge generation is defined as the direction from the interface to the side where free charges are left. For a p-n type device, the direction of free electron (hole) generation from exciton dissociation at donor/accepter (D/A) interface is the same as the subsequent transportation direction under the built-in electric field. However, the direction of free electron (hole) generation from exciton-excition recombination across the D/A interface is opposite to the direction of free charge transportation. Both free charges generated from exciton interfacial dissociation and recombination are contributed to the photocurrent for a p-n type device. In a device with heterojunction formed by two n type materials (here it is defined as n-n type device), the direction of free electron (hole) generation from exciton recombination across the interface is also the same as subsequent free charge transportation. At the same time, there are also some free electrons (free holes) generated by exciton interfacial dissociation. The direction of free charge generation from exciton dissociation for this n-n type device is also opposite to the direction of free charge transportation. However only free charges generated from exciton interfacial recombination are contributed to the photocurrent for a n-n type device. But so far there are no direct experimental evidences to prove the above theories. In this work, an NPB interfacial layer with high LUMO was introduced in an n-n type OSC to inhibit the backflowing of electrons, which are generated from exciton dissociation at the heterojunction formed by two n type materials, enhancing the device performance accordingly. This work is conducive to interfacial engineering in OSC to further improve its performance.

Back to tab navigation

Publication details

The article was received on 20 Nov 2017, accepted on 07 Feb 2018 and first published on 12 Feb 2018


Article type: Paper
DOI: 10.1039/C7CP07817J
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
  •   Request permissions

    The direct observation of electron backflow in an organic heterojunction formed by two n type materials

    P. Li, B. Wu, J. Xiang, X. D. Yang, H. S. Huang, G. D. Zhou and Q. L. Song, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C7CP07817J

Search articles by author

Spotlight

Advertisements