This research is to synthesize polyaniline (PANI) thin film for polymer solar cells as a hole transport layer by using potentiostatic deposition of electrochemical method. In our previous studies, we have shown that the power conversion efficiencies of the solar cell device were improved for the slow polymerization rate. We choose the potentiostatic deposition method to improve the polymerization rate of PANI for the application in industry. In this study, we investigated optical transmittance, absorption spectrum, Highest Occupied Molecular Orbital (HOMO), surface roughness, and surface morphology of the PANI thin film by changing voltages and to discuss the factors on device efficiency. Then, we compared the device structures with hole transport layer PEDOT: PSS by spin-coating process. We found PANI thin films synthesized from different voltages, and the transmittance measurement results were similar. In addition, we found HOMO, surface roughness, and surface morphology of PANI thin film that varies with different voltages. The power conversion efficiencies of the device mainly were affected by the surface roughness and morphology of PANI thin film surface. Comparing to other parameters, PANI thin film polymerized at 0.8V owns the most appropriate surface roughness and surface morphology. The power conversion efficiency was up to 1.52% under AM 1.5G illumination based on ITO (150 nm) / PANI (75 nm) / P3HT: PCBM (100 nm) / Al (200 nm), and the device area of 0.16 cm2.

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This research is to synthesize PANI (polyaniline) thin film for polymer organic solar cells as a hole transport layer on the top of ITO substrate by using electrochemical (cyclic voltammetry) method. The device structure is ITO (150 nm) / PANI (50 nm) / P3HT: PCBM (100 nm) / Al (200 nm). We investigated surface morphology, conductivity, and light transmission of the PANI thin film from different aniline monomer concentration and studied the factors on device efficiency, also compared with the device structured with hole transport layer PEDOT:PSS. In this study, we found PANI thin films synthesized with different aniline monomer concentration, their light transmission over 80% at the range of 450 nm ~ 650nm wavelength and the conductivity up to 0.6 S/cm. It shows that PANI thin film suitably act as hole transport layer. In addition, we found morphology of PANI thin film that varied with different aniline monomer concentration. The power conversion efficiency of the device mainly affected by morphology with different aniline monomer concentration. Comparing to other parameters of concentration, the 0.3M aniline monomer concentration polymerized PANI thin film owned the most appropriate surface morphology, and the power conversion efficiency up to 1.76%.

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第19829号 / エネ博第335号 / 新制||エネ||67(附属図書館) / 32865 / 京都大学大学院エネルギー科学研究科エネルギー応用科学専攻 / (主査)教授 松田 一成, 教授 佐川 尚, 教授 大垣 英明 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DGAM

abstract: The inexorable upsurge in world’s energy demand has steered the search for newer renewable energy sources and photovoltaics seemed to be one of the best alternatives for energy production. Among the various photovoltaic technologies that emerged, organic/polymer photovoltaics based on solution processed bulk-heterojunctions (BHJ) of semiconducting polymers has gained serious attention owing to the use of inexpensive light-weight materials, exhibiting high mechanical flexibility and compatibility with low temperature roll-to-roll manufacturing techniques on flexible substrates. The most widely studied material to date is the blend of regioregular P3HT and PC61BM used as donor and acceptor materials. The object of this study was to investigate and improve the performance/stability of the organic solar cells by use of inexpensive materials. In an attempt to enhance the efficiency of organic solar cells, we have demonstrated the use of hexamethyldisilazane (HMDS) modified indium tin oxide (ITO) electrode in bulk heterojunction solar cell structure The device studies showed a significant enhancement in the short-circuit current as well as in the shunt resistance on use of the hexamethyldisilazane (HMDS) layer. In another approach a p-type CuI hole-transport layer was utilized that could possibly replace the acidic PEDOT:PSS layer in the fabrication of high-efficiency solar cells. The device optimization was done by varying the concentration of CuI in the precursor solution which played an important role in the efficiency of the solar cell devices. Recently a substantial amount of research has been focused on identifying suitable interfacial layers in organic solar cells which has efficient charge transport properties. It was illustrated that a thin layer of silver oxide interfacial layer showed a 28% increase in power conversion efficiency in comparison to that of the control cell. The optoelectronic properties and morphological features of indium-free ZnO/Ag/MoOx electrodes was also studied. Organic solar cells on these composite electrodes revealed good optical and electrical properties, making them a promising alternative indium free and PEDOT:PSS-free organic solar cells. Lastly, inverted solar cells utilizing zinc oxide and yttrium doped zinc oxide electron transport was also created and their device properties revealed that optimum annealing conditions and yttrium doping was essential to obtain high efficiency solar cells. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2015

The search for renewable energy resources and ways to harvest them has become a global mainstream topic among researchers nowadays, with solar cells and thermoelectric generators among the energy harvesting technologies currently being researched in vast. CZTS (Cu2ZnSnS4), a p-type semiconducting material initially researched to replace copper indium gallium selenide (CIGS) as the light absorbing layer in thin film solar cells, was studied in this doctoral work for alternative uses in energy harvesting. This work aims to systemically investigate the prospects of CZTS to be used as hole transport layers and thermoelectric generators. CZTS thin film was successfully fabricated using a versatile approach involving hot-injection synthesis of CZTS nanoparticles ink followed by spin coating and thermal treatment. Results obtained revealed the possibility to fine control CZTS thin film fabrication based on ink concentration and spin. Besides that, thermal treatment temperature was found to affect the film’s overall properties, where an increase in thermal treatment temperature improved the degree of crystallinity and electrical properties. In addition, a phase change going from less stable cubic and wurtzite structures to a more stable tetragonal structure was also observed. Furthermore, CZTS was found to be a good candidate to replace the commonly used organic hole transport layer in perovskite solar cells, with potentials in improving performance and stability. In addition, CZTS also possessed good transport properties to be a potential p-type material in a thermoelectric generator, with the preliminary performance of fabricated CZTS/AZO thermoelectric generator showing a maximum power output of ~350 nW at ~170 KΔT. These findings provide new perspectives for CZTS in energy harvesting applications, despite the struggle in its development as the absorber layer in thin film solar cells. Besides providing a deeper understanding of CZTS and its vast possibilities in energy harvesting applications, promising future research stemming from this work is also limitless, reinventing ways in material studies, in search of alternative applications which may be of benefit.