Relation between charge carrier mobility and lifetime in organic photovoltaics

Vijila, Chellappan, Singh, Samarendra P., Williams, Evan, Sonar, Prashant, Pivrikas, Almantas, Philippa, Bronson, White, Ronald, Kumar, Elumalai Naveen, Sandhya, S. Gomathy, Gorelik, Sergey, Hobley, Jonathan, Furube, Akihiro, Matsuzaki, Hiroyuki, and Katoh, Ryuzi (2013) Relation between charge carrier mobility and lifetime in organic photovoltaics. Journal of Applied Physics, 114 (18). 184503. pp. 1-6.

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Abstract

The relationship between charge carrier lifetime and mobility in a bulk heterojunction based organic solar cell, utilizing diketopyrrolopyrole-naphthalene co-polymer and PC71BM in the photoactive blend layer, is investigated using the photoinduced charge extraction by linearly increasing voltage technique. Light intensity, delay time, and temperature dependent experiments are used to quantify the charge carrier mobility and density as well as the temperature dependence of both. From the saturation of photoinduced current at high laser intensities, it is shown that Langevin-type bimolecular recombination is present in the studied system. The charge carrier lifetime, especially in Langevin systems, is discussed to be an ambiguous and unreliable parameter to determine the performance of organic solar cells, because of the dependence of charge carrier lifetime on charge carrier density, mobility, and type of recombination. It is revealed that the relation between charge mobility (mu) and lifetime (tau) is inversely proportional, where the mu tau product is independent of temperature. The results indicate that in photovoltaic systems with Langevin type bimolecular recombination, the strategies to increase the charge lifetime might not be beneficial because of an accompanying reduction in charge carrier mobility. Instead, the focus on non-Langevin mechanisms of recombination is crucial, because this allows an increase in the charge extraction rate by improving the carrier lifetime, density, and mobility simultaneously.

Item ID: 31669
Item Type: Article (Research - C1)
ISSN: 1089-7550
Funders: A*STAR-JST Strategic International Cooperative Programme
Projects and Grants: A*STAR-JST Project No. 1021630071
Date Deposited: 26 Feb 2014 09:32
FoR Codes: 02 PHYSICAL SCIENCES > 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics > 020201 Atomic and Molecular Physics @ 80%
02 PHYSICAL SCIENCES > 0204 Condensed Matter Physics > 020405 Soft Condensed Matter @ 20%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970102 Expanding Knowledge in the Physical Sciences @ 100%
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