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Spectroscopic Photovoltage Chracterization of PPV Thin Films Suitable for Pled Applications
Published online by Cambridge University Press: 15 February 2011
Abstract
We have studied photovoltage spectra of PPV thin films using both conventional single layer LED structure (ITO/PPV/Al), and capacitive structure consisting of ITO/Mica/PPV/ITO films. The photovoltage spectra for both types of devices have sharp features and are identical indicating that the features observed are primarily due to PPV material itself. We observed two sharp peaks in the energy range of 2.5 -2.7 eV (i.e. above HOMO-LUMO gap) in photovoltage spectrum. The lineshape of the peaks strongly suggests that the peaks are most probably associated with photoionization of excitons. Temperature dependence of spectral lineshape of photocurrent peaks has been studied in the range of 80K-300K. The magnitudes of photocurrent peaks are weakly dependent on temperature, while other spectral features such as peak position and peak width are nearly independent of temperature. On the basis of absorbance, photovoltage and PL spectra, we conclude that both polarons and photoionization of excitons contribute to steady state photovoltage spectra.
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- Copyright © Materials Research Society 2003