Journal article

Reduced Recombination and Capacitor-like Charge Buildup in an Organic Heterojunction

Kyra N Schwarz, Paul B Geraghty, Valerie D Mitchell, Saeed-Uz-Zaman Khan, Oskar J Sandberg, Nasim Zarrabi, Bryan Kudisch, Jegadesan Subbiah, Trevor A Smith, Barry P Rand, Ardalan Armin, Gregory D Scholes, David J Jones, Kenneth P Ghiggino

Journal of the American Chemical Society | AMER CHEMICAL SOC | Published : 2020

Abstract

Organic photovoltaic (OPV) efficiencies continue to rise, raising their prospects for solar energy conversion. However, researchers have long considered how to suppress the loss of free carriers by recombination-poor diffusion and significant Coulombic attraction can cause electrons and holes to encounter each other at interfaces close to where they were photogenerated. Using femtosecond transient spectroscopies, we report the nanosecond grow-in of a large transient Stark effect, caused by nanoscale electric fields of ∼487 kV/cm between photogenerated free carriers in the device active layer. We find that particular morphologies of the active layer lead to an energetic cascade for charge car..

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Grants

Awarded by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences Solar Photochemistry program


Awarded by U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering


Awarded by National Science Foundation Graduate Research Fellowship


Funding Acknowledgements

K.N.S. would like to acknowledge Matthew Menke and Lee Richter for helpful discussions and Simone Gelinas for contributions to developing the genetic algorithm software. This work was made possible by support from the Australian Renewable Energy Agency, which funds the project grants within the Australian Centre for Advanced Photovoltaics. K.N.S acknowledges the Australian Renewable Energy Agency for a postgraduate scholarship. G.D.S and K.N.S. acknowledge support by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences Solar Photochemistry program under Award Number DE-SC0015429. S.U.Z.K. and B.P.R. acknowledge funding from the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award Number DE-SC0012458. A.A. is a Ser Cymru II Rising Star Fellow supported by the European Regional Development Fund, Welsh European Funding Office, and Swansea University strategic initiative in Sustainable Advanced Materials. B.K. acknowledges support by the National Science Foundation Graduate Research Fellowship under Grant Number DGE-1656466.