dc.description.abstract | Solar cells based on polymer materials have attracted a great deal of attention due to their low cost and potential for large-scale fabrication, through solution processes at low temperature. For commercial applications, the efficiency of polymer solar cells (PSC) must exceed 10%. But currently, most PSC devices remain far from that level of efficiency. For this reason, a number of researchers have focused on improving the electrical and physical characteristics of such devices through the development of new materials and the structural optimization. To meet the market demand for portable products, functional circuitry must be designed for low power consumption operating on self-contained power supplies. With this in mind, designing a conductor-insulator-semiconductor (CIS) structure that combines polymer solar cells (PSC) with polymer thin film transistors (TFTs) working at low voltage is the primary objective behind this thesis. The advantages of such integration would be the simplification of circuitry and the simplification of the fabrication process. Propress made in this study show possibility for the development of thin, lightweight products in the future.
In chapter 2, we study a conductor/insulator/conductor (CIC) multi-layer electrode as a replacement for those traditional ones used in PSCs. The work function of this multi-layer electrode was improved by the dipole effect on the surface of the electrode, thereby influencing the internal electric field, and to enhancing the efficiency of the solar cells. In chapter 3, the thickness of the insulator in the structure of the CIS can be controlled through thermal treatment after spin-coated onto the organic electrode. With this controlled technique, the efficiency and the lifespan of the PSC is enhanced. In chapter 4, a low voltage polymer TFT is fabricated with a CIS structure using a poly(3-hexylthiophene) (P3HT) semiconductor, and us electrical characteristic are discussed. The P3HT semiconductor is difficult to apply as a polymer TFT due to low conductivity. Enhancing the conductivity of polymer OTFTs by annealing is well known, but difficult to apply on a plastic substrate, due to low heat tolerance. For this reason, we propose a bias annealing technique with the advantages of rapid heating and highly localized heat radiation. A high input current can be obtained using polymer TFTs by bias annealing of the active layer, the principle of which is discussed later. In chapter 5, we focus on integrating the PSC and polymer TFTs on the same substrate, through the use of the CIS structural concept mentioned previously. This integrated device is given both the characteristic of PSC and polymer TFTs by forming the active layer through drop coating. In chapter 6, the experiment results mentioned previously are concluded, with suggestions for improving the integration of the structure in future studies.
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