Optical interference for the matching of the external and internal quantum efficiencies in organic photovoltaic cells

We demonstrate experimentally that an appropriate combination of the layer thicknesses in an inverted P3HT:PCBM cell leads to an optical interference such that the EQE amounts to 91% of IQE. We observe that reflectivity between layers is minimized in a wavelength range of more than 100nm. In that ra...

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Bibliographic Details
Published in:Solar energy materials and solar cells 2012-09, Vol.104, p.87-91
Main Authors: Betancur, Rafael, Martínez-Otero, Alberto, Elias, Xavier, Romero-Gómez, Pablo, Colodrero, Silvia, Miguez, Hernán, Martorell, Jordi
Format: Article
Language:English
Subjects:
Applied sciences
Direct energy conversion and energy accumulation
Electrical engineering. Electrical power engineering
Electrical power engineering
Energy
Exact sciences and technology
Interference
Mathematical models
Natural energy
Optical interference
Organic solar cells
Photoelectric conversion
Photons
Photovoltaic cells
Photovoltaic conversion
Photovoltaics
Reflectivity
Solar cells
Solar cells. Photoelectrochemical cells
Solar energy
Wavelengths
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Summary:We demonstrate experimentally that an appropriate combination of the layer thicknesses in an inverted P3HT:PCBM cell leads to an optical interference such that the EQE amounts to 91% of IQE. We observe that reflectivity between layers is minimized in a wavelength range of more than 100nm. In that range the EQE closely matches the IQE. The role played by the optical interference in improving the performance of the fabricated solar cells is confirmed by EQE calculated numerically using a model based on the transfer matrix method. Additionally, we observed that a similar cell with an active material 1.7 times thicker exhibited a lower PCE. The poor photon harvesting in the later cell configuration is attributed to an EQE that amounts only to 72% of the IQE. [Display omitted] ► Optical interference to match the EQE to the IQE in an organic solar cell. ► Device multilayer stack optimization to reduce sunlight reflection. ► This effect enables devices with active layers thinner than the absorption length.
ISSN:0927-0248
1879-3398
DOI:10.1016/j.solmat.2012.04.047