Optical absorption by defect states in organic solar cells

Organic bulk heterojunction solar cells enjoy a well established reputation, reaching conversion efficiencies up to 4% at present. Information on electronic states in the gap, whether or not connected with defects, that can influence the power conversion efficiency, are still lacking. A photoelectri...

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Bibliographic Details
Published in:Journal of non-crystalline solids 2006-06, Vol.352 (9-20), p.1656-1659
Main Authors: Goris, L., Poruba, A., Purkrt, A., Vandewal, K., Swinnen, A., Haeldermans, I., Haenen, K., Manca, J.V., Vaněček, M.
Format: Article
Language:English
Subjects:
Absorption
Applied sciences
Band structure
Composition
Defects
Energy
Exact sciences and technology
FTIR measurements
Nano-composites
Natural energy
Optical spectroscopy
Photovoltaic conversion
Photovoltaics
Polymers and organics
Solar cells
Solar cells. Photoelectrochemical cells
Solar energy
STEM/TEM
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Summary:Organic bulk heterojunction solar cells enjoy a well established reputation, reaching conversion efficiencies up to 4% at present. Information on electronic states in the gap, whether or not connected with defects, that can influence the power conversion efficiency, are still lacking. A photoelectrical study of the optical absorption processes in encapsulated cells is presented. Fourier-transform photocurrent spectroscopy is used to measure the transitions connected with free charge carrier generation. The dynamic range obtained with this method reaches over at least eight orders of magnitude. Measurements on solar cells with an active layer of MDMO-PPV:PCBM (1:4 weight ratio) enabled a study of the intrinsic defect generation due to UV-illumination. Temperature annealing effects in P3HT:PCBM (1:2 weight ratio) cells and the induced morphological changes are related with the changes in absorption spectrum. These morphological changes were separately probed with optical and transmission electron microscopy.
ISSN:0022-3093
1873-4812
DOI:10.1016/j.jnoncrysol.2005.09.053