  A method for determination of the bimolecular recombination constant in
working double-injection diodes such as organic light-emitting diodes (OLEDs)
and organic photovoltaics (OPVs) using impedance spectroscopy is proposed. The
proposed method is based on the theory that was developed to interpret the
negative capacitance that has previously been observed in both OLEDs and OPVs.
The determination of the bimolecular recombination constants is demonstrated
using working polymer light-emitting diodes based on
poly(9,9-dioctylfluorene-alt-benzothiadiazole). These impedance spectroscopy
measurements thus allow us to determine the required bimolecular recombination
coefficients along with the electron and hole drift mobilities in working
organic double-injection diodes.
