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In Situ Characterization of Lifetime and Morphology in Operating Bulk Heterojunction Organic Photovoltaic Devices by Impedance Spectroscopy
Author(s) -
Leever Benjamin J.,
Bailey Christopher A.,
Marks Tobin J.,
Hersam Mark C.,
Durstock Michael F.
Publication year - 2012
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201100357
Subject(s) - materials science , dielectric spectroscopy , heterojunction , photovoltaic system , optoelectronics , analytical chemistry (journal) , spectroscopy , conductivity , dielectric , equivalent circuit , open circuit voltage , electrical impedance , organic solar cell , electrode , voltage , composite material , electrical engineering , organic chemistry , polymer , chemistry , physics , quantum mechanics , electrochemistry , engineering
Time‐dependent charge transport in operating poly(3‐hexylthiophene):[6,6]‐phenyl‐C 61 ‐butyric acid methyl ester (P3HT:PCBM) bulk heterojunction organic photovoltaic (OPV) devices has been characterized with impedance spectroscopy. Devices with varied composition and morphology were measured over a range of illumination intensities ranging from dark conditions to 1 sun and applied bias voltages ranging from 0.0 V to 0.75 V. Using an equivalent circuit model, materials properties such as dielectric constant and conductivity were determined and found to be in agreement with values measured by other methods. Average carrier lifetimes were also extracted from the model and found to correlate with measured power conversion efficiencies. At the short circuit condition and ∼1 sun illumination, the average electron lifetime was found to vary from 7.8 to 22 μs for devices with power conversion efficiencies ranging from 2.0 to 2.5%. These results suggest that impedance spectroscopy is an effective tool for predicting how processing parameters can impact device performance in organic bulk heterojunction photovoltaic devices.