A universal solution processed interfacial bilayer enabling ohmic contact in organic and hybrid optoelectronic devices

Abstract
Optoelectronic devices typically require low-resistance Ohmic contacts between the optical active layers and metal electrodes. Failure to make such a contact often results in a Schottky barrier which inhibits charge extraction and, in turn, reduces device performance. Here, we introduce a universal solution processable metal-oxide/organic interfacial bilayer which forms a near-perfect ohmic contact between both organic and inorganic semiconductors and metals. This bilayer comprises a Nb-doped TiO2 metal oxide with enhanced electron mobility and reduced trap density compared to pristine TiO2, in combination with a metal-chelating organic molecule to make an intimate electrical contact with silver metallic electrodes. Using this universal interfacial bilayer, we demonstrate substantial efficiency improvements in organic solar cells (from 9.3% to 12.6% PCE), light emitting diodes (from 0.6 to 2.2 Cd W-1) and transistors (from 19.7 to 13.9 V threshold voltage). In particular, a boost in efficiency for perovskite solar cells (from 18.7% up to 20.7% PCE) with up to 83% fill factor is achieved with no-operational lifetime loss for at least 1000 hours under continuous, full-spectrum illumination.

Citation
Troughton, J. R., Neophytou, M., Gasparini, N., Seitkhan, A., Isikgor, F., Song, X., … Baran, D. (2019). A universal solution processed interfacial bilayer enabling ohmic contact in organic and hybrid optoelectronic devices. Energy & Environmental Science. doi:10.1039/c9ee02202c

Acknowledgements
L.T. acknowledges support for the computational time granted from GRNET in the National HPC facility – ARIS – under project STEM-2. D.B. acknowledges KAUST for financial support. Y.-H.L. and H.J.S. acknowledge the support from the UK Engineering and Physical Sciences Research Council (grant no. EP/M015254/2).

Publisher
Royal Society of Chemistry (RSC)

Journal
Energy & Environmental Science

DOI
10.1039/c9ee02202c

Additional Links
http://pubs.rsc.org/en/Content/ArticleLanding/2019/EE/C9EE02202C

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