Polymer Bulk Heterojunction Diodes

For photovoltaic cells made with pure conjugated polymers, energy conversion efficiencies were typically 10 -10 %, too low to be used in practical applications [48, 63, 67]. Thus, photoinduced charge transfer across a donor/acceptor 

15 Conjugated Polymer Based Plastic Solar Cells 

In two-component charge transfer systems, such as in the bulk-heterojunction solar cells presented here, deviations of the Vgc from the results of pristine single layer or bilayer devices are expected for two reasons first, some part of the available difference in electrochemical energy is used internally by the charge transfer to a lower energetic position on the electron acceptor second, the rela- 

Recently, uniform fdms with high concentrations of Cgo were cast from 1,2-di-chlorobenzene solutions containing up to 1 4 weight ratio MEH-PPV Cgo [110]. For devices made from these high concentration blends, charge collection efficiencies around 7 =26% (electron/incident photon) and power conversion efficiencies around 7e = 2.5% (electrical power out/incident light power) have been realized. 

2 Conjugated Polymer/Conjugated Polymer Bulk Heterojunction Photodiodes 

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The observed experimental result that Voc decreases linearly for bulk heterojunction solar cells allows us to conclude that, at least in the high temperature range (T > 200 K), these solar cells may be described by a diode model with Ip exp(E/kT). Here E is a parameter analogous to Eg for conventional semiconductors. For conjugated polymer/fullerene bulk heterojunction solar cells, E should correspond to the energy difference between the HOMO level of the donor and the LUMO level of the acceptor components of the active layer [as also suggested by the extrapolated value of V oc(0 K)]. 

A. C. Morteani, P. K. H. Ho, R. H. Friend, and C. Silva. Electric field-induced transition from heterojunction to bulk charge recombination in bilayer polymer light-emitting diodes. Appl. Phys. Lett., 86 163501, 2005. 

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