利用紫外光可交聯富勒烯衍生物改良二氧化鈦電子傳導層應用於鈣鈦礦太陽能電池

Abstract

本研究利用紫外光可交聯富勒烯衍生物改良低溫製程以及多孔性二氧化鈦電子傳導層，並將其應用於鈣鈦礦太陽能電池中。二氧化鈦的表面存在的缺陷以及氫氧基團，是造成電子在鈣鈦礦層與電子傳導層間傳遞的主要阻礙，我們希望透過紫外光可交聯富勒烯材料[6,6]-phenyl-C61-butyric oxetane dendron ester (PCBOD)中的oxetane基團，在照光下進行開環反應後，能夠與氫氧基團鍵結，減少氫氧基所造成的電子傳輸效率低落。從SEM中，首先能夠發現鈣鈦礦在已交聯的PCBOD（C-PCBOD）表面上，有較好的結晶型態；另外由於PCBOD其中含有的富勒烯結構有良好的電子親和力，能夠幫助將電子傳導至電子傳導層中，因此在EIS的測量結果，電子傳導電阻相較於未使用C-PCBOD的元件有明顯下降，除此之外，EIS的結果也證明C-PCBOD層能夠大幅降低電荷的再結合率，減少能量經由輻射途徑耗損，另外經由TRPL中載子的生命週期減小，可推斷C-PCBOD有助於電子電洞的拆解。本研究成功的利用紫外光可交聯富勒烯衍生物改良低溫二氧化鈦電子傳導層表面，將鈣鈦礦太陽能電池效率由12.3% 提升至15.9%。接著進一步將C-PCBOD應用至多孔性二氧化鈦之鈣鈦礦太陽能電池，將太陽能轉換效率從17.18 %提升至18.11 %，證明C-PCBOD在改善電子傳輸層與鈣鈦礦層介面的廣用性。

In this research, we use low-temperature TiO2 nanoparticles doped with gold nanoparticles as electron transport layer. To passivate the inefficiency in charge transferring caused by the hydroxyl groups on the surface of TiO2, we use a UV-crosslinkable fullerene derivative [6, 6]-phenyl-C61-butyric oxetane dendron ester (PCBOD) to modify the TiO2 electron transport layer. The oxetane groups on PCBOD will anchor the hydroxyl groups on the TiO2 surface in helps of photoacid generator and also form multi-layer cross-linked PCBOD (C-PCBOD). From the results of EIS, one can be informed that the contact resistance between TiO2 and perovskite layers was decreased after the insertion of C-PCBOD. Furthermore, the recombination resistance was elevated after C-PCBOD modification. Both are evidences of how C-PCBOD increases the Jsc of a perovskite solar cell. The TRPL results also indicate that the lifetime of charge carriers became longer in the device with C-PCBOD. We successfully improve the cell performance and enhance the PCE of perovskite solar cell from 12.3% to 15.9%. We also use C-PCBOD interfacial layer to modify the perovskite solar cell based on mesoporous TiO2 electron transporting layer and get an enhanced PCE from 17.18 % to 18.11 %, proving that the C-PCBOD interfacial layer can be widely used for modifying the interface between electron transporting layer and perovskite.