A Theoretical Model for Organic Bulk-Heterojunction Solar Cells
Date Issued
2011
Date
2011
Author(s)
Chang, Nai-Yung
Abstract
In this work, we established a mathematical model for the description of bulk-heterojunction solar cells. This model considers detailed mechanisms of the photovoltaic and the charge transport phenomenon, including the photon absorption, exciton diffusion, dissociation of charge transfer states, free charge transport and thermionic emission at the interface between the active layer and electrode. By solving the equation numerically, we obtain the profile of potential and free charge concentration, thus the photocurrent under the specific applied voltage. In additions, we also studied the details of the cells under 3 important conditions─short circuit(zero applied voltage), maximum power point and open circuit.
In this study, firstly we simulate the I-V curve for the OC1C10-PPV: PCBM and obtain a set of parameters. By using those parameters, we can then predict the external quantum efficiency with the experiment in a good agreement. Besides, our result shows that the model can also predict the change in short circuit current due to the changes in illumination intensity and operation temperature. Although the prediction for open circuit voltage is not perfect, it can still simulates the tendency of Voc at high temperature region without the use of dark current model.
Secondly, we simulate the I-V curve and obtain another set of parameters for P3HT:PCBM. By using the same set of parameters and only changing the absorption coefficient and mobility from the experiment, the performance of cells after thermal annealing can be well predicted. These results prove that this model can simulate the illumination intensity、 temperature、optical properties and mobility effects on the device. We believe that this model can really help tone in the design of high efficient bulk- heterojunction solar cells in a low cost and time saving manner.
Subjects
Organic bulk-heterojunction solar cells
Optical interference model
Extension Onsager theory
Numerical modeling
Optimization
SDGs
Type
thesis
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