The effect of hole-polaron charging at a hole-injection/hole-transport interface within a functioning organic diode was investigated by single molecule spectroscopy and associated modeling. Efficient quenching of both singlet and triplet excitons by hole polarons is observed at high forward bias due to a buildup of interfacial polaron density. Additionally, for some diodes, an unexpected quenching process was observed at reverse bias, which is ascribed to hole charging of the interface due to the leakage current.

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