The open circuit voltage (Voc) of polymer photovoltaic cells suffers loss due to charge recombination at interfaces within the device. We control the molecular structure local to the donor-acceptor interface via insertion of Langmuir-Schaefer monolayers and multilayers. The multilayer spacer presents both a spatial and an energy barrier which affect charge transfer, separation, transport and recombination at the interface. The modified devices exhibit a stepwise increase in Voc from about 0.42 V to 0.9 V with increasing spacing. Analysis of dark J-V curves and the temperature and light intensity dependence of the Voc reveal that reduced recombination, changes in trap state occupation, and an increase in the polaron pair energy account for the changes in Voc.

Reduction of open circuit voltage loss in a polymer photovoltaic cell via interfacial molecular design

246th National Meeting (2013)

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