Chen et al. Nanoscale Research Letters 2011, 6:350 NANO EXPRESS Open Access Analytical model for the photocurrent-voltage characteristics of bilayer MEH-PPV/TiO2 photovoltaic devices Chong Chen1, Fan Wu1, Hongwei Geng1, Wei Shen1 and Mingtai Wang1,2* Abstract The photocurrent in bilayer polymer photovoltaic cells is dominated by the exciton dissociation efficiency at donor/acceptor interface. An analytical model is developed for the photocurrent-voltage characteristics of the bilayer polymer/TiO2 photovoltaic cells. The model gives an analytical expression for the exciton dissociation efficiency at the interface, and explains the dependence of the photocurrent of the devices on the internal electric field, the polymer and TiO2 layer thicknesses. Bilayer polymer/TiO2. | Chen et al. Nanoscale Research Letters 2011 6 350 http content 6 1 350 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Analytical model for the photocurrent-voltage characteristics of bilayer MEH-PPV TiO2 photovoltaic devices Chong Chen1 Fan Wu1 Hongwei Geng1 Wei Shen1 and Mingtai Wang1 2 Abstract The photocurrent in bilayer polymer photovoltaic cells is dominated by the exciton dissociation efficiency at donor acceptor interface. An analytical model is developed for the photocurrent-voltage characteristics of the bilayer polymer TiO2 photovoltaic cells. The model gives an analytical expression for the exciton dissociation efficiency at the interface and explains the dependence of the photocurrent of the devices on the internal electric field the polymer and TiO2 layer thicknesses. Bilayer polymer TiO2 cells consisting of poly 2-methoxy-5- 2-ethylhexyloxy -1 4-phenylenevinylene MEH-PPV and TiO2 with different thicknesses of the polymer and TiO2 films were prepared for experimental purposes. The experimental results for the prepared bilayer MEH-PPV TiO2 cells under different conditions are satisfactorily fitted to the model. Results show that increasing TiO2 or the polymer layer in thickness will reduce the exciton dissociation efficiency in the device and further the photocurrent. It is found that the photocurrent is determined by the competition between the exciton dissociation and charge recombination at the donor acceptor interface and the increase in photocurrent under a higher incident light intensity is due to the increased exciton density rather than the increase in the exciton dissociation efficiency. Introduction The polymer-based photovoltaic PV cells consisting of conjugated polymer as electron donor D and nanocrystals as electron acceptor A are of great interest due to their advantages over conventional Si-based cells such as low cost easy-processability and capability to make flexible devices 1-3 .
