雙缺陷鈍化劑提升鈣鈦礦太陽能電池之光伏特性及穩定性

Abstract

鈣鈦礦太陽能電池因具備高光電轉換效率、低製備成本與製程簡易等優勢，成為近年來備受矚目的研究領域。然而，其商業化發展仍受限於材料缺陷所造成的穩定性問題與性能衰退。缺陷可分為材料本體的內部缺陷與界面層間的界面缺陷，兩者皆可能導致非輻射復合增加、載子壽命縮短與能量損耗，進而降低元件效能。本研究提出雙缺陷鈍化策略，透過在主動層中同時引入界面活性劑辛基三甲基溴化銨(octadecyltrimethylammonium bromide, 8CTMAB)與五氟苯甲酸(5-fluorobenzoic acid, PFBA)，分別針對界面與內部缺陷進行鈍化，以提升鈣鈦礦太陽能電池之光電轉換效率與穩定性。研究之太陽能電池元件以平面型p-i-n結構為基礎，使用 ITO/P3HT-COOH/Perovskite/PCBM/PEI/Ag之元件架構進行製作與分析。經實驗發現，PFBA的加入有助於鈍化晶格內部缺陷並促進大晶粒生成，而8CTMAB則藉由其陽離子長碳鏈結構排列於鈣鈦礦表面，改善界面能階匹配並減少界面缺陷。研究結果亦證實雙添加劑可有效延長載子壽命、降低陷阱密度及增加電荷再結合阻抗。因此，雙添加劑元件相較於pristine對照元件，可同時提升短路電流密度、開路電壓與填充因子，其PCE最高可達22.21%。在穩定性部分，本研究於65 °與85 °C氮氣環境下進行長時間加熱測試，雙添加劑元件在加熱1000多小時後仍維持其初始效率，顯示其熱穩定性大幅提升。同時，於6500 K LED光源及100 lx照度下，光電轉換效率可達51.99%，展現其優異的室內光應用潛力。此外，XPS與FTIR證實PFBA中的F與COOH官能基及8CTMAB的Br離子可有效鈍化鈣鈦礦膜之缺陷。綜合上述，本研究提出的雙缺陷鈍化策略，不僅能有效降低鈣鈦礦太陽能電池的內部與界面缺陷，進而提升元件光伏性能，同時亦增強其操作與環境穩定性，為高效能、長壽命鈣鈦礦太陽能電池的開發提供極具潛力的材料工程方向。

Perovskite solar cells (PSCs) have become a significant focus of research due to their high power conversion efficiency (PCE), cost-effective fabrication techniques, and simple processing methods. However, commercialization is hindered by stability issues and performance degradation caused by material defects. These defects can be categorized as bulk defects within the material and interfacial defects at the layer boundaries. Both types of defects contribute to elevated non-radiative recombination, reduced carrier lifetimes, and energy losses, thereby adversely affecting device performance. This study presents a dual-defect passivation strategy that incorporates octadecyltrimethylammonium bromide (8CTMAB) and 5-fluorobenzoic acid (PFBA) into the active layer. 8CTMAB improves interfacial defects, while PFBA addresses bulk defects, aiming to improve the efficiency and stability of PSCs.Solar cell devices were constructed and assessed using a planar p-i-n architecture with the configuration ITO/P3HT-COOH/perovskite/PCBM/PEI/Ag. Experimental results showed that adding PFBA passivated bulk defects and promoted the growth of larger perovskite grains. The long alkyl chain of 8CTMAB facilitates its self-assembly on the perovskite surface, thereby enhancing interfacial energy level alignment and mitigating interfacial defects. Subsequent analyses have verified that employing dual passivation agents extends carrier lifetime, reduces trap density, and increases charge recombination resistance effectively. Consequently, in comparison to cells manufactured from pristine perovskite, the dual-additive devices demonstrated improved short-circuit current density, open-circuit voltage, and fill factor, achieving a maximum PCE of 22.21%.Thermal aging tests were conducted under nitrogen at temperatures of 65 °C and 85 °C. The dual-additive devices retained their initial efficiency after over 1000 hours of exposure to elevated temperatures, indicating enhanced thermal stability. Moreover, under conditions of low indoor illumination with a 6500 K LED light bulb at 100 lx, an outstanding PCE of 51.99% was achieved, demonstrating the devices' significant potential for indoor photovoltaic applications. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) confirmed that the fluorine atoms and carboxyl functional groups in PFBA, along with the bromide ions in 8CTMAB, effectively passivated defects in the perovskite film.In conclusion, the dual-defect passivation strategy presented in this study effectively addresses both bulk and interfacial defects in perovskite solar cells, thereby enhancing their photovoltaic performance and improving operational and environmental stability. This research offers a promising avenue in materials engineering for the development of high-efficiency and long-lifetime PSCs.