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Analytical model for the photocurrent-voltage characteristics of bilayer MEH-PPV/TiO2 photovoltaic devices.

Chen C, Wu F, Geng H, Shen W, Wang M - Nanoscale Res Lett (2011)

Bottom Line: An analytical model is developed for the photocurrent-voltage characteristics of the bilayer polymer/TiO2 photovoltaic cells.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, PR China. mtwang@ipp.ac.cn.

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.

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The calculated ηCT as a function of applied voltage V with deferent l (a), d (b) and various illumination intensities (c).
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Figure 5: The calculated ηCT as a function of applied voltage V with deferent l (a), d (b) and various illumination intensities (c).

Mentions: Note that, all the following theoretical curves were obtained by considering the experimentally determined compensation voltage V0. As shown by the solid lines in Figure 4, the excellent fits to the photocurrent-voltage characteristics of three types devices are obtained using the parameters described above. During the calculations, we use different k0/v0 values to fit the photocurrent-voltage characteristics of the differently structured devices (Figure 4a,b,c) and the same cell under the varied illumination intensities (Figure 4c,d,e). In Figure 4, it can be seen that the photocurrent increases as the applied voltage turns from reverse to forward direction, and subsequently tends to saturate at higher forward voltages. This phenomenon can be attributed to the dependence of the exciton dissociation efficiency ηCT on the internal electric field (Equation 14), since the efficiency ηED of exciton dissociation by charge transfer at the D/A interface is constant and the efficiency ηCC of charge collection at electrodes is equal to 1 (Equation 4) [39]. As suggested from Figure 3a, the exciton dissociation efficiency at the D/A interface increases with increasing the forward electric field strength (i.e., the forward applied voltage), and finally approach unit when the forward electric field strength is large enough. In order to examine the dependence of ηCT on the applied voltage V, the TiO2 and polymer film thicknesses and illumination intensity, we plot the expression ηCT from Equation 14 for all devices, as shown in Figure 5.


Analytical model for the photocurrent-voltage characteristics of bilayer MEH-PPV/TiO2 photovoltaic devices.

Chen C, Wu F, Geng H, Shen W, Wang M - Nanoscale Res Lett (2011)

The calculated ηCT as a function of applied voltage V with deferent l (a), d (b) and various illumination intensities (c).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211440&req=5

Figure 5: The calculated ηCT as a function of applied voltage V with deferent l (a), d (b) and various illumination intensities (c).
Mentions: Note that, all the following theoretical curves were obtained by considering the experimentally determined compensation voltage V0. As shown by the solid lines in Figure 4, the excellent fits to the photocurrent-voltage characteristics of three types devices are obtained using the parameters described above. During the calculations, we use different k0/v0 values to fit the photocurrent-voltage characteristics of the differently structured devices (Figure 4a,b,c) and the same cell under the varied illumination intensities (Figure 4c,d,e). In Figure 4, it can be seen that the photocurrent increases as the applied voltage turns from reverse to forward direction, and subsequently tends to saturate at higher forward voltages. This phenomenon can be attributed to the dependence of the exciton dissociation efficiency ηCT on the internal electric field (Equation 14), since the efficiency ηED of exciton dissociation by charge transfer at the D/A interface is constant and the efficiency ηCC of charge collection at electrodes is equal to 1 (Equation 4) [39]. As suggested from Figure 3a, the exciton dissociation efficiency at the D/A interface increases with increasing the forward electric field strength (i.e., the forward applied voltage), and finally approach unit when the forward electric field strength is large enough. In order to examine the dependence of ηCT on the applied voltage V, the TiO2 and polymer film thicknesses and illumination intensity, we plot the expression ηCT from Equation 14 for all devices, as shown in Figure 5.

Bottom Line: An analytical model is developed for the photocurrent-voltage characteristics of the bilayer polymer/TiO2 photovoltaic cells.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, PR China. mtwang@ipp.ac.cn.

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.

No MeSH data available.


Related in: MedlinePlus