單晶混合陽離子鈣鈦礦的合成與分析

Synthesis and Analysis of Mixed Cation Perovskite Single Crystal

鄧克頎(Ko-Chi. Teng)

指導教授 ： 衛子健

國立清華大學/工學院/化學工程學系/碩士(2018年)

摘要

鹵化有機金屬鈣鈦礦因具有相當優異的光吸收係數、載子壽命、電子與電動遷移率等特性，而受到了學術界的矚目，開始被應用於太陽能電池中，作為高效吸光層材料。但截至目前為止，幾乎所有的鈣鈦礦太陽能電池中的鈣鈦礦材料皆屬多晶薄膜，其晶界容易導致載子的再結合，是影響其光電轉換效率與元件穩定性的瓶頸之一。相較於多晶薄膜，單晶鈣鈦礦因晶界與表面缺陷相當稀少，因此具有更優異的光電性質與穩定性，若能以其作為光吸收層將有機會獲得更高的光電轉換效率。
但目前研究最廣泛的鈣鈦礦MAPbI3由於陽離子MA+平均半徑值較小而導致晶體成為不穩定的扭曲結構，水氣等外在因子容易造成晶體結構的瓦解。因此為了同時解決多晶MAPbI3晶界導致載子再結合和MAPbI3材料不穩定的問題，本研究利用升溫析晶法在溶液中合成出不同FA+((NH2)2CH+)/MA+比例的單晶混合陽離子鈣鈦礦FAXMA(1-X)PbI3，並利用多種儀器進行性質分析，我們發現當單晶FAXMA(1-X)PbI3對於濕度有較好的穩定性，代表其更適合做為長效鈣鈦礦太陽能電池中的吸光材料。
另外，溶液中合成出的單晶鈣鈦礦因為厚度的因素限制了其應用光伏元件的發展性，為了取得單晶鈣鈦礦薄片，本研究另設計出可以簡易合成厚度為0.17mm單晶MAPbI3 wafer的培養槽。並結合FAXMA(1-X)PbI3前驅液與wafer培養槽，合成單晶FAXMA(1-X)PbI3 wafer並量測其電性，並與MAPbI3做比較。

關鍵字

單晶鈣鈦礦 ； 升溫析晶法 ； 單晶混合陽離子鈣鈦礦 ； 單晶鈣鈦礦薄片

並列摘要

The organic-inorganic hybrid perovskites have been receiving considerable attention in various optoelectronic applications due to its superior characteristics including high absorption coefficient, direct bandgap, long carrier lifetime, and high hole and electron mobility. However, current perovskite solar cells are all based on polycrystalline perovskite thin films, which contain plenty of grain boundaries and surface defects, rendering noticeable carrier loss and device instability. It was reported that single crystalline perovskite possesses superior optoelectronic properties and stability due to less grain boundaries and surface defects.
However, the widely explored MAPbI3 is still unstable due to its distorted crystal structure caused by small MA+ ions. It was found that the crystal structure is weak against moisture. Herein we added formamidinium ions (FA+) ions in the MA+ incubation solution and successfully synthesized MAXFA(1-X)PbI3 single crystal by means of inverse temperature crystallization. We examined the mixed cation single crystals by several instruments and found they possess better stability under high humidity.
In addition, the applications on MSCs are limited by the thickness of crystals. Herein, we designed a incubating tank to synthesize large area MAPbI3 wafer with 0.17mm in thickness. We also synthesized MAXFA(1-X)PbI3 wafer and measured its electrical properties comparing to MAPbI3.

並列關鍵字

perovskite single crystal ； inverse temperature crystallization ； mixed cation perovskite single crystal FAXMA(1-X)PbI3 ； perovskite single crystal wafer

參考文獻

[1] International Energy Statistics-Total Electricity Net Consumption. Available: http://www.eia.gov/cfapps/ipdbproject/iedindex3.cfm?tid=2&pid=2&aid=2&cid=ww,&syid=2004&eyid=2011&unit=BKWH

[2] Global Energy Flows in watts / m2 / sec. Available: http://www.hydrogenambassadors.com/background/global-energy-flows.php

[3] B. O'regan and M. Grätzel, "A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO 2 films," nature, vol. 353, pp. 737-740, 1991.

[4] S. Mathew, A. Yella, P. Gao, R. Humphry-Baker, B. F. Curchod, N. Ashari-Astani, et al., "Dye-sensitized solar cells with 13% efficiency achieved through the molecular engineering of porphyrin sensitizers," Nature chemistry, vol. 6, pp. 242-247, 2014.

[5] A. Kojima, K. Teshima, Y. Shirai, and T. Miyasaka, "Organometal halide perovskites as visible-light sensitizers for photovoltaic cells," Journal of the American Chemical Society, vol. 131, pp. 6050-6051, 2009.