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  • 學位論文

共軛高分子於鈣鈦礦太陽能電池之應用研究

Applications Research in Perovskite Solar Cell with Conjugated Polymers

指導教授 : 戴子安
共同指導教授 : 王立義

摘要


鈣鈦礦太陽能電池被認為是下個世代最具潛力的替代能源,目前這類太陽能電池都是使用小分子當作其電洞傳導層,如spiro-OMeTAD,但是spiro-OMeTAD價格昂貴、不易合成、成膜性差。本論文分為兩部份,分別在尋找合適的共軛高分子來取代spiro-OMeTAD當作電洞傳導層。 第一部分,我們使用二維共軛高分子PBDTDTTPD當作電洞傳導層,製備出以CH3NH3PbI3鈣鈦礦為吸光材料的太陽能電池其元件效率達11.24 % 比一般常用的聚己基噻吩 ( P3HT ) 還要高 ( 8.11% ),我們利用2-D WAXS分析高分子在垂直方向有 ( 020 )晶面產生,表面功函數分析 ( AC-2 ) 得知其HOMO能階,時間解析光激螢光 ( TRPL ) 分析得知電洞注入高分子的效率,電化學阻抗頻譜 ( EIS ) 得知元件內部的各界面電荷傳遞的情形。我們發現由於BDT與DTTPD單體都有很好的平面性使其共軛高分子主鏈有很好的π - π堆疊造成比P3HT還要高的電洞遷移率且較低的HOMO能階,提升了短路電流、填充因子和開環電壓。我們還發現將元件做退火處理能大幅的提升元件效率,我們利用TRPL和EIS分析發現退火不只有幫助PBDTDTTPD因結晶強度提升使電荷傳遞更快進而提升填充因子,還能減少界面電阻使電洞更容易注入進而提升短路電流。 第二部分,我們使用側鏈只有四個碳的聚丁基噻吩 ( P3BT ) 當作電洞傳導層,雖然它在傳統高分子太陽能電池效率表現不是很理想,但是由於其本質的電洞遷移率比P3HT高很多,所以我們希望它能進一步的增加元件的光電流,我們製備了以CH3NH3PbI3鈣鈦礦為吸光材料的太陽能電池其元件效率達11.94 % 比P3HT還要高,我們利用TRPL和 EIS等圖譜去觀察各界面電荷轉移現象,我們發現較短的側鏈能有效地降低界面間的電阻進而提升電洞注入的能力以提升短路電流。

並列摘要


Perovskite solar cells are novel alternatives for next-generation solar cells, this solar cells generally use small molecules as its hole transporting layer, such as spiro-OMeTAD, but spiro-OMeTAD is expensive, difficultly synthesized, and poor film coverage. This study is divided into two parts, namely looking for a suitable conjugated polymer to replace spiro-OMeTAD as hole transporting layer. The first part, we use a two-dimensional conjugated polymers as hole transporting layer, called PBDTDTTPD, incorporated into CH3NH3PbI3 perovskite-based the solar cell, reaching efficiency of 11.24 % higher than the well-known poly(3-hexylthiophene) ( P3HT ) ( efficiency of 8.11% ). We use 2-D WAXS to analyze polymer crystalline state, surface work function measurement ( AC-2 ) to investigate HOMO energy level, time-resolved photoluminescence ( TRPL ) to analyze the polymer hole injection efficiency, electrochemical impedance spectroscopy ( EIS ) to explore the charge transfer at the interface. We found that BDT and DTTPD monomer with a large planar structure make conjugated polymer backbone has great face-on π-π stacking causing hole mobility of PBDTDTTPD even higher than that of P3HT and low-lying HOMO energy level to improve the short-circuit current, fill factor, and open-circuit voltage. In addition, we also found that the devices with annealing can has significantly enhanced cell efficiency. We used TRPL and EIS to analyze the devices with annealing. Annealing procedure not only enhanced the charge transporting for PBDTDTTPD by intensified crystallinity to increase fill factor, but also reduced the charge transfer resistance at the interface making it easier for hole injection to enhance the short-circuit current. The second part, we use poly(3-butylthiophene) ( P3BT ) as hole conducting layer. Although his performance in the conventional polymer solar is not attractive, but due to its nature hole mobility higher than P3HT, so we would expect that it can further increase the photocurrent. We prepared P3BT-based CH3NH3PbI3 perovskite as the light absorber solar cell, reaching efficiency of 11.94 % higher than P3HT. Then, we used TRPL and EIS spectra to observe the interface charge transfer phenomenon. We found that the shorter side chain can effectively reduce the resistance at the interface to enhance capacity of hole injection to improve short-circuit current.

參考文獻


Chapter 1
1. Würfel, P. Physics of Solar Cells, Wiley-VCH Verlag GmbH Co. HGaA: Weinheim, Germany 2003.
2. Hamakawa, Y. Thin-film Solar Cells: Next Generation Photovoltaics and its Application, Springer Science Business Media, Germany 2004.
3. Grätzel, M. Inorganic Chemistry 2005, 44, 6841.
4. Chapin, D. M.; Fuller, C. S.; Pearson, G. L. Journal of Applied Physics 1954, 25, 676.

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