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- Bergqvist, Jonas, et al.
(author)
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Uniaxial Anisotropy in PEDOT:PSS Electrodes Enhances the Photocurrent at Oblique Incidence in Organic Solar Cells
- 2018
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In: ACS Photonics. - : AMER CHEMICAL SOC. - 2330-4022. ; 5:8, s. 3023-3030
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Journal article (peer-reviewed)abstract
- PEDOT:PSS is a well studied organic conductor, commonly used as a transparent electrode material in printed organic devices such as organic solar cells. PEDOT:PSS thin films are known to be uniaxially anisotropic and exhibit a lower extinction coefficient and lower refractive index in the out of plane direction. To determine the maximum attainable photocurrent in thin film solar cells, the optical power dissipation can be calculated by the transfer matrix method. However, until now the anisotropic properties of PEDOT:PSS films have not been included in the model. In this work we have included an uniaxial anisotropic treatment of PEDOT:PSS films. We investigate reversed and semitransparent solar cells, with aluminum and PEDOT:PSS respectively as the second electrode and PEDOT:PSS as the top electrode, as compared to devices with isotropic PEDOT:PSS electrodes. For p-polarized light at large oblique incidence the inclusion of anisotropy shows a gain of over 7% for the maximum photocurrent in reversed solar cells. In semitransparent solar cells the photocurrent enhancement reaches 4-5% for p-polarized light. However, an enhancement of optical power dissipation and thus photocurrent generation of close to 40% is calculated for wavelengths close to the absorber bandgap. This work shows that for correct calculations of optical power dissipation in devices with PEDOT:PSS electrodes anisotropy should be included in the optical model. This will be especially important to determine the daily energy output of organic solar cells as their expected first markets are on building facades and indoor applications with larger fractions of diffuse light at large oblique incidence.
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