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Effect of the Molecular Structure of Fulleropyrrolidine on the Photovoltaic Behavior of Poly(3-hexylthiophene)-based Bulk Heterojunction Solar Cells
Date Issued
2011
Date
2011
Author(s)
Liu, Che-Liang
Abstract
This thesis consists of two parts concerning the use of new C60 derivatives as electron acceptor of polymer solar cells. In the first part, the effect of the alkyl moieties, including ethyl, isopropyl, and tert-butyl groups, of N-methyl-2-(4- alkylbenzenyl)-3,4-fulleropyrrolidine on the performance of poly(3-hexylthiophene) (P3HT)-based solar devices was investigated. XRD experiments showed that as the number of branch of alkyl group increased that raised its electron donating ability, the crystallinity of these molecules increased, thus resulting in the drop of solubility. Moreover, the ordered structure of fulleropyrrolidine lengthened the inter distance of fullerene balls that visibly reduced the electron mobility. In the thin film, however, the crystalline structure boosted the LUMO energy level of C60 derivatives and enhanced open circuit voltage. On the other hand, the TEM images demonstrated the presence of alkyl groups greatly improved the compatibility of C60 derivatives and P3HT, increasing the interfacial area of bulk heterojunction and the power conversion efficiency of devices. As a tert-butyl group was employed, the blend of P3HT and fulleropyrrolidine formed a morphology of nano-scaled bi-continuous interpenetrating network and the device based on this blending film exhibited an open circuit voltage of 670 mV and an power conversion efficiency of 3.47%.
In the second part, to overcome the low absorptivity of PCBM in visible region, a 2,2'':5'',2"-terthiophene (TT) substituted fullerene, abbreviated as TTC60, was utilized as acceptor to blend with P3HT to fabricate polymer solar cells. Photoluminence (PL) measurements indicated the photo-excited electrons generated in terthiophene units can be efficiently transferred to the neighbor C60 cage to produce free electron/hole pairs. The cells of P3HT/TTC60 processed from a solvent mixture of TCB and o-DCB at a volume ratio of 1:10 gave the best power conversion efficiency of 2.14%. Therefore, similar to the UV-vis absorption spectrum, the P3HT/TTC60 device exhibited higher IPCE than P3HT/PCBM device in the wavelength region of 350 to 400 nm.
In the second part, to overcome the low absorptivity of PCBM in visible region, a 2,2'':5'',2"-terthiophene (TT) substituted fullerene, abbreviated as TTC60, was utilized as acceptor to blend with P3HT to fabricate polymer solar cells. Photoluminence (PL) measurements indicated the photo-excited electrons generated in terthiophene units can be efficiently transferred to the neighbor C60 cage to produce free electron/hole pairs. The cells of P3HT/TTC60 processed from a solvent mixture of TCB and o-DCB at a volume ratio of 1:10 gave the best power conversion efficiency of 2.14%. Therefore, similar to the UV-vis absorption spectrum, the P3HT/TTC60 device exhibited higher IPCE than P3HT/PCBM device in the wavelength region of 350 to 400 nm.
Subjects
Polymer solar cells
fulleropyrrolidine
poly(3-hexylthiophene)
SDGs
Type
thesis
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Name
ntu-100-R98549029-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
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