以電化學聚合法製備聚（2,2-雙噻吩）/二氧化鈦 混成太陽能電池

Abstract

本研究中利用電化學聚合法製備一系列以聚（2,2-雙噻吩）/二氧化鈦為光敏感層之混成太陽能電池，其中無機二氧化鈦部份利用溶膠-凝膠法合成出粒徑大小均一之TiO2膠體溶液，經旋轉塗佈後製備出具奈米孔隙之TiO2薄膜，並作為本研究中元件系統之acceptor；再利用電化學聚合的方法，在固定之電流密度下將吸光層材料poly(2,2-bithiophene)成長於基材上，並作為本研究中元件系統之donor。實驗中我們藉由改變TiO2膠體溶液之濃度來調控TiO2薄膜之厚度，且成功地以電化學聚合法將主鏈剛硬無柔軟側鏈之poly(2,2-bithiophene)成長於其上，除了製程方便快速之外，電化學聚合法提供了可準確控制polymer沉積量之優點，因此我們得以固定TiO2厚度以外之實驗參數，對系統進行一致性的探討，研究中藉由各項儀器（UV-Vis-NIR Spectrometer、Photoluminescene Spectroscopy、Electrochmical Impedance Spectroscopy）搭配元件結果，探討TiO2厚度不同時對於系統各項性質之影響，實驗結果顯示，當acceptor厚度為165 nm時，元件之各項表現均最佳，在AM 1.5G 100 mW/cm2照光情況下元件之open-circuit voltage (Voc)、short-circuit current (Jsc)、fill factor (FF)及power conversion efficiency (η)分別為：420 mV、0.171 mA/cm2、0.48及3.44E-2 %；PL之quench效率為64.5 %，表示exciton的分離效率因為TiO2的加入而得到了提升。此外，本研究亦藉由導入2-thiophenecarboxylic acid將親水之TiO2表面改質為疏水性，以增加有機/無機介面處之親和性，實驗結果顯示，改質後元件之Voc、Jsc、FF及η分別為：470 mV、0.090 mA/cm2、0.48及2.02E-2 %，僅管改質後之結果並不如預期，但是由Voc的上升可知surface modifier對元件表現確有影響。

A series of novel organic/inorganic hybrids solar cells were fabricated and investigated. Various thicknesses of TiO2 films were coated on top of FTO glass by spin-casting using different concentrations of TiO2 colloids that synthesized by sol-gel method. This study developed an electrochemical polymerization route for preparing organic/inorganic hybrids for use as photoactive materials in photovoltaic devices. This new technique was benefited from the ability of using non-soluble conjugated polymers as major photoactive component in solar cells. Moreover, the monomer can be polymerized from the interstices of TiO2 matrices due to their much smaller size in comparison to the corresponding polymer, thus substantially increasing the donor-acceptor interface for exciton dissociation. The effect of titania film thickness on the performance of the photovoltaic cells constructed from these materials was examined. An approximate thickness of 165 nm of TiO2 exhibited an optimal cell performance with a short-circuit current, an open-circuit voltage, a fill factor and a power conversion efficiency of 0.171 mA/cm2, 0.42 V, 0.48 and 3.44E-2 %, respectively. Additionally, 2-thiophenecarboxylic acid was employed as a surface modifier to alter the TiO2 surface from hydrophilic to hydrophobic. The devices with 2-thiophenecarboxylic acid had an optimal short-circuit current, open-circuit voltage, fill factor and power conversion efficiency of 0.09 mA/cm2, 0.47 V, 0.48 and 2.02E-2 %, respectively. Although the cell performance was not improved, the Voc was slightly increased, revealing that surface modifier certainly ameliorated the interface properties of organic/inorganic.