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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.

No MeSH data available.


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Current-voltage characteristics of ITO/TiO2/MEH-PPV/Au device. The solid line (JD) was recorded in the dark, and the dot line (JL) was measured under illumination at 470 nm with an intensity of 158.5 W/m2. The thickness of TiO2 layer was d = 65 nm, while that of the polymer layer was l = 220 nm. The inset shows the Jph as a function of bias, where the arrow indicates the compensation voltage (V0).
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Figure 2: Current-voltage characteristics of ITO/TiO2/MEH-PPV/Au device. The solid line (JD) was recorded in the dark, and the dot line (JL) was measured under illumination at 470 nm with an intensity of 158.5 W/m2. The thickness of TiO2 layer was d = 65 nm, while that of the polymer layer was l = 220 nm. The inset shows the Jph as a function of bias, where the arrow indicates the compensation voltage (V0).

Mentions: Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) (Avg. Mn = 40000-70000) was purchased from Aldrich (product of USA). Titanium tetraisopropoxide [Ti(Oi-Pr)4] (Acros, 98+%) was used as TiO2 precursor. The bilayer PV devices with a structure of ITO/TiO2/MEH-PPV/Au, as shown in Figure 1, were constructed by spinning down first a nanostructured titanium dioxide (TiO2) layer and then a MEH-PPV layer over indium tin oxide (ITO, ≤15 Ω/∀, Wuhu Token Sci. Co., Ltd., Wuhu, China) sheet glass, as described elsewhere [11]. The current-voltage (J-V) characteristics were measured on a controlled intensity modulated photo spectroscopy (CIMPS) (Zahner Co., Kronach, Germany) in ambient conditions. The devices were illuminated through ITO glass side by a blue light-emitting diode (LED) as light source (BLL01, λmax = 470 nm, spectral half-width = 25 nm, Zahner Co., Kronach, Germany). A reverse voltage sweep from 1 to -1 V was applied and the current density under illumination (JL) was recorded at 300 K. In order to determine the photocurrent, the current density in the dark (JD) was also recorded, and the experimental photocurrent is given by Jph = JL - JD [24,26,32], as shown in Figure 2. From the resulting Jph-V characteristics the compensation voltage (V0) was determined as the bias voltage where Jph = 0 (inset to Figure 2). During all measurements, the gold and ITO contacts were taken as negative and positive electrodes, respectively, and the effective illumination area of the cells was 0.16 cm2.


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)

Current-voltage characteristics of ITO/TiO2/MEH-PPV/Au device. The solid line (JD) was recorded in the dark, and the dot line (JL) was measured under illumination at 470 nm with an intensity of 158.5 W/m2. The thickness of TiO2 layer was d = 65 nm, while that of the polymer layer was l = 220 nm. The inset shows the Jph as a function of bias, where the arrow indicates the compensation voltage (V0).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Current-voltage characteristics of ITO/TiO2/MEH-PPV/Au device. The solid line (JD) was recorded in the dark, and the dot line (JL) was measured under illumination at 470 nm with an intensity of 158.5 W/m2. The thickness of TiO2 layer was d = 65 nm, while that of the polymer layer was l = 220 nm. The inset shows the Jph as a function of bias, where the arrow indicates the compensation voltage (V0).
Mentions: Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) (Avg. Mn = 40000-70000) was purchased from Aldrich (product of USA). Titanium tetraisopropoxide [Ti(Oi-Pr)4] (Acros, 98+%) was used as TiO2 precursor. The bilayer PV devices with a structure of ITO/TiO2/MEH-PPV/Au, as shown in Figure 1, were constructed by spinning down first a nanostructured titanium dioxide (TiO2) layer and then a MEH-PPV layer over indium tin oxide (ITO, ≤15 Ω/∀, Wuhu Token Sci. Co., Ltd., Wuhu, China) sheet glass, as described elsewhere [11]. The current-voltage (J-V) characteristics were measured on a controlled intensity modulated photo spectroscopy (CIMPS) (Zahner Co., Kronach, Germany) in ambient conditions. The devices were illuminated through ITO glass side by a blue light-emitting diode (LED) as light source (BLL01, λmax = 470 nm, spectral half-width = 25 nm, Zahner Co., Kronach, Germany). A reverse voltage sweep from 1 to -1 V was applied and the current density under illumination (JL) was recorded at 300 K. In order to determine the photocurrent, the current density in the dark (JD) was also recorded, and the experimental photocurrent is given by Jph = JL - JD [24,26,32], as shown in Figure 2. From the resulting Jph-V characteristics the compensation voltage (V0) was determined as the bias voltage where Jph = 0 (inset to Figure 2). During all measurements, the gold and ITO contacts were taken as negative and positive electrodes, respectively, and the effective illumination area of the cells was 0.16 cm2.

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