Criteria for validating polaron pair dissociation in polymer-fullerene bulk heterojunction solar cells

Inche Ibrahim, Mohd Lukman (2016) Criteria for validating polaron pair dissociation in polymer-fullerene bulk heterojunction solar cells. Journal of Applied Physics, 19 (15). pp. 1-8. ISSN 0021-8979 E-ISSN 1089-7550

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Abstract

The dissociation of polaron pairs into free charge carriers in organic bulk heterojunction solar cells is a fundamental step in generating photocurrent and is still in debate. In this study, we propose two simple criteria that can be used to test the validity of any polaron pair dissociation model for polymer-fullerene bulk heterojunction solar cells. The first criterion states that the ratio of the bimolecular recombination current density to the maximum photocurrent density should increase as a function of applied voltage. The second criterion states that the ratio of the bimolecular recombination current density to the maximum photocurrent density at short circuit should not be larger than 1. We apply these criteria to test the validity of the widely used Onsager-Braun model by using the experimental current-voltage data of poly[2-methoxy-5-(30-70-dimethyloctyloxy)-p-phenylene vinylene] (OC1C10-PPV) and [6,6]-phenyl C61-butyric acid methylester (PCBM) based solar cells. We find that our numerical analysis is not suitable to employ these criteria. Our analytical analysis, on the other hand, clearly demonstrates that the Onsager-Braun model simply cannot fulfill the first criteria. The reason is because the polaron pair dissociation given by the Onsager-Braun model is too strongly influenced by the electric field (i.e., decreases too rapidly as the electric field decreases). The analysis provides a further evidence against the widely used Onsager- Braun model. The proposed criteria can help us to determine the correct model for polaron pair dissociation by serving as a guideline on how strongly the electric field is allowed to influence the polaron pair dissociation.

Item Type:	Article (Journal)
Additional Information:	7410/53677
Uncontrolled Keywords:	Charge transfer states, recombination, generation, separation, transport, mechanism, IONS.
Subjects:	Q Science > QC Physics T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK2896 Production of electricity by direct energy conversion T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK7800 Electronics. Computer engineering. Computer hardware. Photoelectronic devices
Kulliyyahs/Centres/Divisions/Institutes (Can select more than one option. Press CONTROL button):	Kulliyyah of Engineering > Department of Science
Depositing User:	Dr Mohd Lukman Inche Ibrahim
Date Deposited:	22 Dec 2016 16:25
Last Modified:	21 Oct 2017 06:36
URI:	http://irep.iium.edu.my/id/eprint/53677

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