離子化合物之修飾以提升鈣鈦礦太陽能電池光電轉換效率之應用

鈣鈦礦太陽能電池因為其具備良好的特性，例如適當的能隙大小、在可見光波段擁有高吸收係數、可溶液製備以降低生產成本等優點而成為近年來太陽能領域中一個熱門的研究題目，且有望能取代現今廣泛使用的矽晶太陽能電池。然而，鈣鈦礦太陽能電池中的缺陷對於元件的最終表現會有決定性的影響。太多的缺陷密度將會大大的降低元件的表現。有鑑於此，對鈣鈦礦太陽能電池中的電子傳輸材料做修飾將會是一個可行的解決辦法，因為它可以在填補缺陷的同時也提高電子傳輸材料的導電性。在本篇研究中，我們透過在二氧化錫膠體溶液內添加不同濃度的氯化鈉做修飾，並利用修飾過的二氧化錫作為鈣鈦礦太陽能電池中的電子傳輸層材料。透過研究電子傳輸層的表面形貌、透光性、導電性；利用XRD及SEM探討沉積在電子傳輸層上的鈣鈦礦層的結晶性、表面形貌；以及透過PL和TRPL了解鈣鈦礦層到電子傳輸層的電子傳遞效率，我們從實驗結果發現以25 mM的氯化鈉來修飾二氧化錫可以得到最好的元件性能提升。電子傳輸層的電性提升來自於薄膜的緻密性及均勻性。鈣鈦礦層中缺陷的減少歸功於部分氯化鈉溶於鈣鈦礦溶液內，提升鈣鈦礦晶體的結晶性，以及導致適量殘留的碘化鉛來鈍化鈣鈦礦晶體的晶粒邊界。電子從鈣鈦礦層傳遞到電子傳輸層的效率也因此有了大幅的提升。實際做成鈣鈦礦太陽能電池並在AM1.5G的標準測試條件下，在光電轉換效率的表現上與未經修飾的二氧化錫相比，平均而言效率從9.23 ± 1.12%上升到11.86 ± 0.44%，有2.63%顯著的提升。而最高效率的比較上，經過25 mM的氯化鈉修飾之後，光電轉換效率從10.26%來到12.39%，也有2.13%的提升。利用氯化鈉修飾二氧化錫作為電子傳輸材料並應用在鈣鈦礦太陽能電池上的確具有良好的效果，期望這樣一個簡單可行的方法能夠幫助未來鈣鈦礦太陽能電池的商業化。

關鍵字

氯化鈉；鈣鈦礦太陽能電池；二氧化錫修飾

並列摘要

Perovskite solar cell is an emerging solar cell technology due to its excellent properties such as suitable bandgap, high absorption coefficient in the visible region and low-cost solution process. The possibility of replacing the extensively used silicon based solar cell nowadays by perovskite solar cell has triggered a surge of interest in researching this unprecedented photovoltaics. Defects in perovskite solar cell plays a crucial role in determining the final performance of device. Large defect density in perovskite solar cell has a destructive effect on device performance and modification of electron transport material is therefore considered as a feasible solution to this problem since it can not only passivate defects but also enhance the electrical property of electron transport material. Herein, a facile ionic compound modification was applied where different amount of sodium chloride was physically blended in tin oxide colloid solution. The sodium chloride modified tin oxide was utilized as electron transport material to fabricate perovskite solar cell. The as-spun sodium chloride modified tin oxide layer was carefully studied in terms of morphology, transmittance and conductivity. The perovskite layer deposited on different concentrations of sodium chloride modified tin oxide layer was attentively investigated through XRD and SEM. The electron transfer efficiency from perovskite layer to electron transport layer was examined by PL and TRPL spectra. Throughout the experiment we found that 25 mM sodium chloride modified tin oxide as electron transport layer could considerably enhance the performance of device compared to the pristine tin oxide. The conductivity of as-spun sodium chloride modified tin oxide layer was enhanced because of its dense and well-distributed film quality. Defect density in perovskite layer was also reduced due to the enlarged perovskite crystal and suitable amount of non-reacted lead iodide passivating grain boundaries of perovskite crystal when a portion of sodium chloride was dissolved in perovskite precursor solution. Both the enhanced conductivity of electron transport layer and reduced defect density in perovskite layer led to a significantly promoted electron transfer efficiency from perovskite layer to electron transport layer. The power conversion efficiency of perovskite solar cell displayed a 2.63% remarkable improvement from 9.23 ± 1.12% to 11.86 ± 0.44% on average and a 2.13% improvement from 10.26% to 12.39% in champion devices when 25 mM sodium chloride modified tin oxide as electron transport layer was used in comparison with pristine tin oxide. This facile sodium chloride modification strategy to tin oxide had achieved a great success and may provide an opportunity of realizing the commercialization of perovskite solar cell.