陽離子界面活性劑之抗衡離子對鈣鈦礦太陽能電池之效能影響探討

Abstract

鈣鈦礦太陽能電池因具備高光伏效率、製程簡便與成本低廉等優勢，已成為新世代太陽能技術的重要研究焦點。然而，其穩定性與缺陷問題仍是限制商業化應用的關鍵挑戰。本研究採用MA₀.₁₆Cs₀.₀₅FA₀.₇₉Pb(I₀.₉Br₀.₁)₃鈣鈦礦為太陽能電池元件之光作用層，佐以四級銨鹽型陽離子界面活性劑為添加劑，詳細探討界面活性劑之抗衡離子的種類對於電子之光伏特性的影響。首先，透過 SEM 觀察表面及橫截面形貌，確立不同抗衡離子對結晶顆粒及膜層厚度的影響，觀察到C8TMAI 結晶顆粒最小，且鈣鈦礦層之膜層厚度並無因添加劑的加入而有顯著差異；搭配 EDX 元素分佈分析，證實C8TMAI可有效擴散至膜層內部，達到最佳的缺陷鈍化效果。再以 XRD、AFM 分析結晶行為及表面粗糙度，觀察到添加 C8TMAI 可減小晶粒尺寸、改善表面平整性，利於載子傳輸。經 UV-Vis 量測，證實添加劑的加入並未影響其吸光能力，以及 PL/TRPL 載子壽命研究，確認不同抗衡離子對載子復合動力學之影響，其中 C8TMAI 可顯著降低缺陷密度、延長載子壽命。以 SCLC、EIS、XPS 測試，說明 C8TMAI 可有效減少缺陷密度、改善界面電荷傳輸及結合力。再者，在元件光伏性能比較下可觀察到，於AM1.5G之測試條件下，添加 C8TMAI有最佳光電轉換效率，可使元件 PCE 由15.28% 提升至20.64%。而在元件之長期熱穩定性的分析中，可觀察到在85 °C氮氣環境的加速老化條件下，在1100小時測試後，經XRD量測，未添加C8TMAI的樣品可明顯觀察到PbI2峰，而添加C8TMAI之鈣鈦礦膜可明顯發現PbI2繞射峰的強度明顯下降，顯示C8TMAI的加入可有效抑制鈣鈦礦的降解，使其不因PbI2的析出導致元件效率下降，在元件之測試性能下，也觀察到在經過1100小時後C8TMAI仍維持初始效率的100%。最後，在6500 K、100 lx 室內照明環境下，C8TMAI 之光電轉換效率更高達53.10%，結合前述AM1.5G的測試結果，證實 C8TMAI 在模擬太陽光與室內光源這兩種光源條件下，皆有最佳的光電轉換效率。本研究系統比較不同抗衡離子之界面活性劑對鈣鈦礦薄膜結構、缺陷鈍化及載子傳輸行為之影響，結果突顯 C8TMAI 在改善元件性能及穩定性之關鍵角色，提供後續設計更穩定、高效、並適用於室內照明之鈣鈦礦元件之明確方向及研究依據。Perovskite solar cells (PSCs) have emerged as a promising next-generation photovoltaic technology due to their high power conversion efficiency (PCE), low fabrication cost, and facile processing. However, issues related to device stability and intrinsic defects remain critical challenges that hinder their commercialization.In this study, we employed a mixed-cation perovskite composition of MA₀.₁₆Cs₀.₀₅FA₀.₇₉Pb(I₀.₉Br₀.₁)₃ as the active layer and used quaternary ammonium-based cationic surfactants as additives. The influence of different counterions on the photovoltaic performance of the device was systematically investigated.First, surface and cross-sectional SEM observations were conducted to investigate the effects of different counterions on grain morphology and film thickness. The results showed that the C8TMAI-treated perovskite film exhibited the smallest grain size, with no significant changes in film thickness caused by the additives. Complementary EDX elemental mapping confirmed that C8TMAI was effectively distributed throughout the film, achieving the best defect passivation. XRD and AFM analyses further revealed that the addition of C8TMAI reduced grain size and improved surface smoothness, facilitating charge transport. UV-Vis absorption measurements indicated that the additives had negligible influence on the optical absorption characteristics of the perovskite films. Meanwhile, PL and TRPL studies confirmed that the different counterions impacted charge carrier recombination dynamics, with C8TMAI yielding the lowest defect density and longest carrier lifetime. Moreover, SCLC, EIS, and XPS analyses demonstrated that C8TMAI effectively reduced defect densities, enhanced interfacial charge transport, and improved binding strength.In terms of device performance, under AM1.5G illumination, the device treated with C8TMAI achieved the highest power conversion efficiency (PCE), increasing from 15.28% (pristine) to 20.64%. In long term thermal stability analyses conducted at 85 °C under a nitrogen atmosphere, XRD measurements after 1,100 hours revealed a pronounced PbI₂ peak in the pristine sample, whereas the C8TMAI treated perovskite film exhibited significantly reduced PbI₂ diffraction intensity. This result indicates that the incorporation of C8TMAI effectively suppresses perovskite decomposition, thereby preventing efficiency loss caused by PbI₂ formation. Under the same device testing conditions, the C8TMAI based device retained 100% of its initial efficiency even after 1,100 hours, confirming its excellent thermal stability.Finally, under indoor illumination (6500 K, 100 lx), C8TMAI devices achieved a maximum efficiency of 53.10%. Together with the AM1.5G results, these findings confirm that C8TMAI delivers the best performance across both solar and indoor lighting conditions, providing a promising pathway for highly efficient, stable, and versatile perovskite solar cells.In summary, the physicochemical properties of counteranions play a crucial role in the depth distribution and defect passivation behavior within perovskite films. C8TMAI, in particular, exhibited outstanding performance by effectively passivating defects, boosting photovoltaic efficiency, and demonstrating excellent potential under low-light conditions. These findings provide a clear design strategy and material selection guideline for the development of stable, high-efficiency perovskite devices suitable for diverse applications, including indoor photovoltaics.