Effect of Organically-Modified Titania Nanoparticles on the Performance of Poly(3-hexythiophene): PCBM Bulk Heterojuncti
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Effect of Organically-Modified Titania Nanoparticles on the Performance of Poly(3hexythiophene): PCBM Bulk Heterojunction Solar Cells Sun Young Park, Haeng Hee Ahn, Jiyeon Yoon, Sang Yong Kim, Bora Hwang, Tae Gi Yoon and Yong Ku Kwon* Department of Polymer Science and Engineering, Inha University, Incheon, 402-751, Korea ABSTRACT The modified TiO2 nanoparticles were incorporated into the Bulk heterojunction system of P3HT:PCBM to improve the performance of P3HT:PCBM bulk heterojunction organic solar cells. The organically-modified TiO2 nanoparticle compounds were synthesized in aqueous media at room temperature. These TiO2 compounds in various solution concentrations were deposited on the top of the P3HT:PCBM active layer by spin coating. The performance of organic solar cells was carefully investigated in the respect of the scattering and the localized surface plasmon resonance (LSPR) that couple strongly to the incident light. In addition to the device, P3HT:PCBM solar cells with the use of the TiO2 nanoparticles, enhanced Fill Factor (FF) due mainly to improved shunt resistance (Rsh). The TiO2 plays a critical role in improving the interface between P3HT:PCBM active layer and Al electrode. INTRODUCTION Polymer solar cells (PSC) have attracted a lot of interest due to many advantages including low production cost, light weight, good processability and flexibility. Several low bandgap polymers have been designed and used in PSCs to harvest more sunlight. Poly(3hexylthiophene)s (P3HT)s are presently among the most promising material for use in PSCs as an electron donor material due to their strong absorption in the visible and near-infrared region and the high charge carrier mobility. Due to high power conversion efficiency, the binary blends of P3HT and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are extensively employed as an active layer in PSCs. However, the photovoltaic performance of the bulk heterojunction (BHJ) solar cells of P3HT: PCBM is still limited as compared with the materials obtained from inorganic solar cells due to the insufficient charge carrier mobility and the narrow absorption range of donor polymers, as well as the relatively short exciton diffusion length of only a few nanometers. They also show limited device stability because oxygen can diffuse into the active layer leading to its degradation. In order to overcome these limitations and improve the photovoltaic performance, the electron-transporting interfacial layers of metal oxides, e.g. TiO2 and CuO have been introduced between the active layers and the electrodes. These metal oxides harvest electrons from many of the electron acceptor components of PSCs and block holes and limit surface recombination at the contact. It is also reported that the interfacial interlayer of these metal oxides located between the active layer and the electrode acts as optical spacer to shift the maximum of light intensity which increase the exciton generation rate and improve the performance of PSCs.
EXPERIMENT To modify the surfaces of TiO2NPs, 1g o
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