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Nongeminate recombination and charge transport limitations in diketopyrrolopyrrole-based solution-processed small molecule solar cells

  • Charge transport and nongeminate recombination are investigated in two solution-processed small molecule bulk heterojunction solar cells consisting of diketopyrrolopyrrole (DPP)-based donor molecules, mono-DPP and bis-DPP, blended with [6,6]-phenyl-C71-butyric acid methyl ester (PCBM). While the bis-DPP system exhibits a high fill factor (62%) the mono-DPP system suffers from pronounced voltage dependent losses, which limit both the fill factor (46%) and short circuit current. A method to determine the average charge carrier density, recombination current, and effective carrier lifetime in operating solar cells as a function of applied bias is demonstrated. These results and light intensity measurements of the current-voltage characteristics indicate that the mono-DPP system is severely limited by nongeminate recombination losses. Further analysis reveals that the most significant factor leading to the difference in fill factor is the comparatively poor hole transport properties in the mono-DPP system (2 x 10(-5) cm(2) V-1 s(-1)Charge transport and nongeminate recombination are investigated in two solution-processed small molecule bulk heterojunction solar cells consisting of diketopyrrolopyrrole (DPP)-based donor molecules, mono-DPP and bis-DPP, blended with [6,6]-phenyl-C71-butyric acid methyl ester (PCBM). While the bis-DPP system exhibits a high fill factor (62%) the mono-DPP system suffers from pronounced voltage dependent losses, which limit both the fill factor (46%) and short circuit current. A method to determine the average charge carrier density, recombination current, and effective carrier lifetime in operating solar cells as a function of applied bias is demonstrated. These results and light intensity measurements of the current-voltage characteristics indicate that the mono-DPP system is severely limited by nongeminate recombination losses. Further analysis reveals that the most significant factor leading to the difference in fill factor is the comparatively poor hole transport properties in the mono-DPP system (2 x 10(-5) cm(2) V-1 s(-1) versus 34 x 10(-5) cm(2) V-1 s(-1)). These results suggest that future design of donor molecules for organic photovoltaics should aim to increase charge carrier mobility thereby enabling faster sweep out of charge carriers before they are lost to nongeminate recombination.show moreshow less

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Metadaten
Author:Christopher M. Proctor, Chunki Kim, Dieter NeherORCiDGND, Thuc-Quyen Nguyen
DOI:https://doi.org/10.1002/adfm.201202643
ISSN:1616-301X (print)
ISSN:1616-3028 (online)
Parent Title (English):Advanced functional materials
Publisher:Wiley-VCH
Place of publication:Weinheim
Document Type:Article
Language:English
Year of first Publication:2013
Year of Completion:2013
Release Date:2017/03/26
Tag:characterization tools; charge transport; organic electronics; photovoltaic devices; solar cells
Volume:23
Issue:28
Pagenumber:11
First Page:3584
Last Page:3594
Funder:Office of Naval Research; National Science Foundation-SOLAR program [DMR-1035480]; German Science Foundation; National Science Foundation [DGE-1144085]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie
Peer Review:Referiert