Analysis of degradation mechanisms in donor–acceptor copolymer based organic photovoltaic devices using impedance spectroscopy

Srivastava, S.B., Sonar, P., & Singh, S.P. (2016) Analysis of degradation mechanisms in donor–acceptor copolymer based organic photovoltaic devices using impedance spectroscopy. Materials Research Express, 3(9), Article no. 096202.

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The stability of organic photovoltaic (OPV) devices in ambient conditions has been a serious issue which needs to be addressed and resolved timely. In order to probe the degradation mechanism in a donor–acceptor polymer PDPP-TNT: PC71BM bulk heterojunction based OPV devices, we have studied current density–voltage (J–V) behavior and impedance spectroscopy of fresh and aged devices. The current–voltage characteristic of optimized fresh devices exhibit a short circuit current density (J sc) of 8.9 mA cm−2, open circuit voltage (V oc) of 0.79 V, fill factor (FF) of 54.6%, and power conversion efficiency (PCE) of 3.8%. For aged devices, J sc, V oc, FF, and PCE were reduced to 57.3%, 89.8%, 44.3% and 23.7% of its initial value, respectively. The impedance spectra measured under illumination for these devices were successfully fitted using a CPE-based circuit model. For aged devices, the low-frequency response in impedance spectra suggests an accumulation of the photo-generated charge carriers at the interfaces which leads to a significant lowering in fill factor. Such degradation in device performance is attributed to the incorporation of oxygen and water molecules in devices. An increase in the recombination resistance indicates a deterioration of free charge carrier generation and conduction in devices.

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ID Code: 99802
Item Type: Journal Article
Refereed: Yes
Keywords: charge transport, charge carrier lifetime, degradation mechanism, impedance spectroscopy, organic solar cell
DOI: 10.1088/2053-1591/3/9/096202
ISSN: 2053-1591
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2016 IOP Publishing Ltd
Copyright Statement: This is an author-created, un-copyedited version of an article accepted for publication/published in Materials Research Express. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at
Deposited On: 11 Oct 2016 23:56
Last Modified: 25 Oct 2016 04:44

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