Real-Time Observation of the Diffusion Mechanism Progression from Liquid to Solid State of Transition Metal Complexes

Journal Article · 22 January 2020 · ACS Energy Letters

DOI: https://doi.org/10.1021/acsenergylett.9b02677 · OSTI ID:1596083

Kim, Tea-Yon  ^[1]; Wang, Yujue ^[2]; Raithel, Austin L. ^[2]; Hamann, Thomas W.  ^[2]

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1. Michigan State Univ., East Lansing, MI (United States); Michigan State University
2. Michigan State Univ., East Lansing, MI (United States)

Copper complexes have recently shown remarkable performance upon conversion from liquid-based to solid-state hole transport materials (HTMs) in mesoscopic solar cells; however, the diffusion mechanism is not clear. Here, we apply an in situ solidification analysis of the charge diffusion and find that the dominant mechanism of [Cu(dmbpy)₂]^2+/+ (dmbpy = 6,6'-dimethyl-2,2'-bipyridine) changes from ionic to electronic diffusion. Through use of the modified Dahms–Luff equation, a fast self-exchange rate constant of hole-hopping in the HTM of 8.3 × 10⁸ (±5 × 10⁷) M^–1 s^–1 is calculated, which indicates a small reorganization energy of 0.47 eV. These findings present a new methodology to analyze the transport mechanism of solids, reveal the mechanism of charge transport in molecular-based HTMs, and offer insight into ways to control the flow of charge in optoelectronic systems

• Research Organization: Michigan State Univ., East Lansing, MI (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
• Grant/Contract Number: SC0017342
• OSTI ID: 1596083
• Journal Information: ACS Energy Letters, Journal Name: ACS Energy Letters Journal Issue: 2 Vol. 5; ISSN 2380-8195
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English