官能化之噻吩並苯并噻二唑衍生物之合成及性質探討並於太陽能電池之應用

Abstract

本研究乃合成官能化之噻吩並苯并噻二唑(Thiophene-Benzothiadiazole)之一系列小分子化合物，透過在小分子化合物末端改質上具有拉電子能力的羧酸(Carboxylic acid, -COOH)及腈(Nitrile, -CN)官能基，使合成之小分子化合物與作為電子施體(Donor)的P3HT產生π-π堆疊(π-π Stacking)現象、同時與作為電子受體(Acceptor)的無機碳材(如PCBM、石墨烯)藉由末端官能基產生相互作用力，進一步扮演P3HT及碳材之間的橋梁，使電子能夠透過合成之小分子化合物順利地由P3HT導向作為電子受體的碳材，藉以提升太陽能電池元件的光電流(Photo-current)，並提高光電轉換效率(Power conversion efficiency, PCE)。 本研究利用熱重分析儀(Thermogravimetry analysis, TGA)及示差熱掃描分析儀(Differential scanning calorimetry, DSC)分析所合成之小分子化合物的熱性質，確保其能夠因應太陽能電池元件製作中的各種製程；利用紫外光/可見光分光光譜儀(UV/Visible spectroscopy, UV-vis)測量小分子在紫外光-可見光區的吸光範圍及強度，藉以瞭解小分子化合物之吸光範圍；利用螢光光譜儀(Fluorescence spectrometer, FL)測量P3HT及小分子化合物混摻導電碳材後的螢光放光情形，探討所合成之小分子化合物是否能夠有效地幫助電子-電洞分離、減少螢光放光；利用循環伏安儀(Cyclic voltammetry, CV)測量小分子的氧化電位以及能階，測試其能階是否落在P3HT及導電碳材之間。 太陽能電池元件部分，將P3HT與改質石墨烯混合後，加入不同比例之小分子化合物，探討小分子化合物對於元件效率的影響。當三者之間的重量比為P3HT：小分子化合物：改質石墨烯 = 1：4：4時有最好的元件效率，可達到4.13 %，比未添加小分子化合物的對照組提升了25.5 %。

In this study, a series of functionalized thiophene-benzothiadiazole derivatives are successfully synthesized. By modifying the synthesized small molecules with electron-withdrawing functional groups, carboxylic acid (-COOH), and nitrile (-CN), they are able to form good π-π stacking with the electron donor, P3HT, and at the same time build up combinations with the electron acceptor, like PCBM or graphene. Acting like a bridge, the small molecule can then help electrons be delivered from P3HT to carbon electron acceptors, which can be expected to lead to the increase of photocurrent and the power conversion efficiency of solar cells. To make sure the synthesized molecules can go through all the manufacturing process of organic solar cells, Thermogravimetry analysis (TGA) and Differential scanning calorimetry (DSC) are used to test the thermal stability of them. UV/Visible spectroscopy (UV-vis) helps us know their light-harvesting ability. Fluorescence spectrometer (FL) is used to measure the light-emitting situation after the mixture of P3HT, synthesized small molecules and electron-conducting materials are excited by photons. Cyclic voltammetry (CV) tells us the oxidation potential and the energy level of these compounds. For the part of solar cell device, P3HT and modified graphene are blended with different ratios of synthesized small molecules to find out their influence on efficiency. When the weight ratio of the three comes to 1: 4: 4 (P3HT: small molecule compound: modified graphene), the power conversion efficiency reaches the highest of 4.13 %, which is 25.5 % higher than the non-doped control one.