以原子層沉積法製備鈣鈦礦太陽能電池之氧化錫電子傳輸層

Atomic-layer-deposited SnOx films as electron-transporting and passivation layers for organic-inorganic hybrid perovskite solar cells

黃任賢(Jen-Hsien Huang)

指導教授 ： 蔡豐羽

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202200649

摘要

有機無機混合鈣鈦礦太陽能電池具有高效率與易量產的優勢，因此為近年來蓬勃發展的太陽能技術，但其實用性仍受限於其不穩定性。本研究使用原子層沉積技術(ALD)以低溫製備氧化錫(SnOx)薄膜，做為鈣鈦礦太陽能電池之電子傳輸層(ETL)並同時提供鈍化效果，透過沉積溫度、氧化劑前驅物種類、與表面前處理方式的調控，以同時達到高效率與增加穩定性的目標。
在本研究分析之60與80°C兩種低沉積溫度中，80°C沉積的SnOx因為反應完成度較高，所以薄膜本身導電度較佳；但做為鈣鈦礦電池之ETL層時，因為低溫製程有利於SnOx在鈣鈦礦/PCBM緩衝層表面的ALD成核，故以60°C沉積SnOx ETL之元件效率較高，空間電荷限制電流(SCLC)測量結果也指出60°C製備的元件缺陷密度較少。在本研究分析之水與雙氧水兩種不同氧化劑中，雙氧水製備的SnOx 薄膜可達較高反應完成度，使得薄膜本身導電度較佳；但應用於鈣鈦礦電池時，水製程SnOx薄膜製備的元件效率可達15.4%、而雙氧水製程製備的元件效率卻僅達6.1%。經過不同薄膜疊層的交叉比對，我們推測雙氧水製程所沉積之SnOx薄膜可能產生與銀電極之能階不匹配的問題，導致元件效率低下。另外，我們開發了以原位雙氧水前處理、搭配水製程SnOx ETL的元件製備方法，利用雙氧水蒸氣先與鈣鈦礦/PCBM緩衝層表面上的C=O反應而形成-OH官能基，以利接續之水製程SnOx ETL於PCBM表面均勻快速成核，其最高元件效率可達16.4%。在鈍化效果上，此ALD SnOx ETL可顯著提升元件於大氣下之穩定度，將元件於大氣中的效率劣化速率減緩達8.8倍。

關鍵字

原子層沉積技術 ； 鈣鈦礦太陽能電池 ； 氧化錫 ； 半導體薄膜 ； 表面處理

並列摘要

Organic-inorganic hybrid perovskite solar cells (PSCs) have the advantages of high efficiency and easy mass production, so they are a booming solar technology in recent years. However, commercialization of PSCs is still limited by their instability, necessitating development of effective passivation techniques. This work studies SnOx films fabricated by atomic layer deposition (ALD) at low processing temperatures as an electron transporting layer (ETL) with passivation function for PSCs, achieving high efficiency and improving the stability of PSCs through manipulating the ALD temperature, type of oxidant precursor, and surface pretreatment method.
Of the two ALD temperatures tested, 60 °C and 80 °C, 80 °C resulted in SnOx films with higher electron conductivity due to more complete reaction; however, in terms of ETL performance in PSCs, 60 °C-deposited SnOx yielded higher efficiency, because its lower deposition temperature allowed more complete nucleation of the SnOx ETL on the perovskite/[6,6]-Phenyl C61 butyric acid methyl ester (PCBM) buffer layer. A space charge-limited current (SCLC) analyze also indicated that the PSCs with SnOx deposited at 80 °C have less defect density. Of the two ALD oxidant tested, H2O and H2O2, H2O2 resulted in SnOx films with higher electron conductivity due to more complete reaction; however, in terms of ETL efficiency in PSCs, H2O-deposited SnOx yielded 15.4%, while H2O2-deposited SnOx only yielded 6.1%. After cross-comparison of different film stacks, we found that the H2O2-deposied SnOx film may have a problem of mismatching the energy level of the silver electrode, resulting in low efficiency. Moreover, we developed a device preparation method using in-situ H2O2 pre-treatment and H2O-deposited SnOx ETL, whose highest PCE can reach 16.4%. The mechanism is that H2O2 vapor reacts with C=O on perovskite/PCBM and forms -OH functional groups, and then H2O- SnOx can evenly and quickly nucleate on the PCBM. In terms of passivation effect, the ALD SnOx ETL can significantly improve the stability of the PSCs in the atmosphere, and slow down the degradation rate of the PSCs in the atmosphere by 8.8 times.

並列關鍵字

atomic layer deposition (ALD) ； organic-inorganic hybrid perovskite solar cells (PSCs) ； tin oxide ； semiconductor thin films ； surface treatment

參考文獻

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