Methods of accurate measurement of conventional polymer solar cells and study of zinc oxide based inverted polymer solar cells
Date Issued
2009
Date
2009
Author(s)
Liu, Meng-Yueh
Abstract
The research in this thesis can be separted into two parts. In the first part, methods of accurate measurement and improving the power conversion efficinecy of polymer solar cells are discussed. In the second part, sol-gel deposition of amorphous titanium oxide thin film on the poly(3-alkylthiophene) (P3HT)/ [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) substrate is demonstrated. In the first part, polymer-based organic solar cells with conventional and inverted structure are fabricated. For the converntional structure, the relationship between the performance and dimethyl sulfoxide (DMSO) modified poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) of polymer solar cells is investigated. The PEDOT:PSS is modified by adding DMSO into its aqueous solution, resulting in the enhancement of conductivity from 0.12 S/cm to 464.7 S/cm. However, the device with DMSO modified PEDOT:PSS has a short circuit current density of 35.5 mA/cm2, which is not physically possible. The unreasonable current density results form the improper collection by the extremely condutive DMSO modified PEDOT:PSS. We demonstrate that the performance is strongly related to the employment of modified PEDOT:PSS and it can be corrected by strict definition of illumination area while measuring. For the inverted structure, the polymer solar cells based on the zinc oxide (ZnO) thin film and ZnO nanorod are investigated. Interestingly, we find that the enhancement in the device performance can be achieved by placing the devices in the air. Meanwhile, we also find that the use of ZnO nanorod may be not a rewarding method for enhancing efficiency of the polymer solar cells. With placement and measurement in the air, our inverted polymer solar cells based on ZnO thin film and ZnO nanorod show efficiency of 3.6% at 6th day and 2.9% at 5th day without encapsulation. In the second part, sol-gel preparation of amorphous titanium oxide (TiOx) films with distinct morphological properties on the P3HT/PCBM coated substrate is obtained by solution spin coating. The TiOx film is deposited by three precursors using 2-methoxyethanol, isopropanol and mixture of 2-methoxyethanol and hexane as solvents. We demonstrate that the morphology of TiOx film is related to the employment of dissimilar solvent. TiOx film obtained from mixed 2-methoxyethanol/hexane is a superior choice for the preparation of TiOx on P3HT/PCBM substrate because of its good smoothness.
Subjects
polymer-based organic solar cell
measurement
Type
thesis
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