OPTOELECTRONIC TECHNIQUES FOR INVESTIGATION OF TRANSPORT AND RECOMBINATION IN ORGANIC PHOTOVOLTAICS
Lindsay C.C. Elliott, Kurt P. Pernstich, David J. Gundlach, Lee J. Richter, Dean M. DeLongchamp
Organic photovoltaics are an important subset of the solar cell industry and show promise in applications such as flexible and portable electronics, textiles, and coatings. Much research has been done to characterize the fundamental electronic properties of the solar cell active layer in order to facilitate better design and control of devices and products. Our work here extends progress in this area by combining the recently developed technique photo-induced charge extraction by linearly increasing voltage (photoCELIV) with newly improved fast photovoltage and fast photocurrent measurements. These three techniques were used to study transport and recombination characteristics in a series of bulk heterojunction devices with a common polymer-fullerene pair, poly(3-hexyl thiophene-2,5-diyl):[6,6]-phenyl-C61 butyric acid methyl ester (P3HT:PCBM61). We compare variations in film nanoscale morphology and microstructure to variations in charge carrier mobility and the rate of non-geminate recombination. Future studies will be carried out to include other polymer-fullerene pairs. These results may add insight into processing-structure-function relationships for organic photovoltaics that many researchers are pursuing.