Bracesco Andrea E A, Jansen Jarvi W P, Xue Haibo, Zardetto Valerio, Brocks Geert, Kessels Wilhelmus M M, Tao Shuxia, Creatore Mariadriana
Plasma & Materials Processing, Department of Applied Physics and Science of Education, Eindhoven University of Technology (TU/e), P.O. Box 513, Eindhoven 5600 MB, Netherlands.
Materials Simulation & Modelling, Department of Applied Physics and Science of Education, Eindhoven University of Technology (TU/e), P.O. Box 513, Eindhoven 5600 MB, Netherlands.
ACS Appl Mater Interfaces. 2023 Aug 9;15(31):38018-38028. doi: 10.1021/acsami.3c05647. Epub 2023 Jul 28.
Perovskite photovoltaics has achieved conversion efficiencies of 26.0% by optimizing the optoelectronic properties of the absorber and its interfaces with charge transport layers (CTLs). However, commonly adopted organic CTLs can lead to parasitic absorption and device instability. Therefore, metal oxides like atomic layer-deposited (ALD) SnO in combination with fullerene-based electron transport layers have been introduced to enhance mechanical and thermal stability. Instead, when ALD SnO is directly processed on the absorber, i.e., without the fullerene layer, chemical modifications of the inorganic fraction of the perovskite occur, compromising the device performance. This study focuses on the organic fraction, particularly the formamidinium cation (FA), in a CsFAPb(I,Br) perovskite. By employing in situ infrared spectroscopy, we investigate the impact of ALD processing on the perovskite, such as vacuum level, temperature, and exposure to half and full ALD cycles using tetrakis(dimethylamido)-Sn(IV) (TDMA-Sn) and HO. We observe that exposing the absorber to vacuum conditions or water half-cycles has a negligible effect on the chemistry of the perovskite. However, prolonged exposure at 100 °C for 90 min results in a loss of 0.7% of the total formamidinium-related vibrational features compared to the pristine perovskite. Supported by density functional theory calculations, we speculate that FA deprotonates and that formamidine desorbs from the perovskite surface. Furthermore, the interaction between TDMA-Sn and FA induces more decomposition of the perovskite surface compared to vacuum, temperature, or HO exposure. During the exposure to 10 ALD half-cycles of TDMA-Sn, 4% of the total FA-related infrared features are lost compared to the pristine perovskite. Additionally, IR spectroscopy suggests the formation and trapping of -triazine, i.e., a decomposition product of FA. These studies enable to decouple the effects occurring during direct ALD processing on the perovskite and highlight the crucial role of the Sn precursor in affecting the perovskite surface chemistry and compromising the device performance.
通过优化吸收层及其与电荷传输层（CTLs）的界面的光电性能，钙钛矿光伏电池已实现26.0%的转换效率。然而，常用的有机电荷传输层会导致寄生吸收和器件不稳定性。因此，诸如原子层沉积（ALD）的SnO等金属氧化物与基于富勒烯的电子传输层相结合，以提高机械和热稳定性。相反，当ALD SnO直接在吸收层上处理时，即没有富勒烯层时，钙钛矿的无机部分会发生化学改性，从而损害器件性能。本研究聚焦于CsFAPb(I,Br)钙钛矿中的有机部分，特别是甲脒阳离子（FA）。通过采用原位红外光谱，我们研究了ALD处理对钙钛矿的影响，例如真空度、温度，以及使用四（二甲基氨基）锡（IV）（TDMA-Sn）和HO进行半周期和全周期ALD处理的情况。我们观察到，将吸收层暴露于真空条件或水半周期对钙钛矿的化学性质影响可忽略不计。然而，与原始钙钛矿相比，在100℃下长时间暴露90分钟会导致与甲脒相关的总振动特征损失0.7%。在密度泛函理论计算的支持下，我们推测FA去质子化且甲脒从钙钛矿表面解吸。此外，与真空、温度或HO暴露相比，TDMA-Sn与FA之间的相互作用会导致钙钛矿表面更多分解。在暴露于TDMA-Sn的10个ALD半周期期间，与原始钙钛矿相比，与FA相关的总红外特征损失了4%。此外，红外光谱表明形成并捕获了-三嗪，即FA的分解产物。这些研究能够区分直接ALD处理钙钛矿过程中发生的各种影响，并突出了Sn前驱体在影响钙钛矿表面化学性质和损害器件性能方面的关键作用。
