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Smoothing and coverage improvement of SnO2 electron transporting layer by NH4F treatment: Enhanced fill factor and efficiency of perovskite solar cells

Keshtmand, R ; Sharif University of Technology | 2021

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  1. Type of Document: Article
  2. DOI: 10.1016/j.solener.2021.09.068
  3. Publisher: Elsevier Ltd , 2021
  4. Abstract:
  5. Surface modification of SnO2 electron transporting layer (ETL) plays a critical role in the performance of SnO2-based planar perovskite solar cells (PSC). Here, we show how long-time NH4F-based water bath treatment of SnO2 layer makes smoothing and morphological improvements and enhances the device performance. Recently it was shown that short-time NH4F treatment (2 sec) with spin coating method reduces interface traps by improving surface chemistry. Here we observe the smoothing of SnO2 films as a result of long-time NH4F treatment, which could be a result of a slight etching-deposition process. Absorption and resistivity measurements indicate that SnO2 etching process is involved in morphology healing. This has led to considerably better FTO coverage and improved hole blocking, as evidenced by cyclic voltammetry measurements. Additionally, we observe the presence of F on the surface (X-ray photoelectron spectroscopy) and possibly inside the layer, as there is higher carrier density in NH4F treated films. Improvements in the PSC device performance are accompanied by higher recombination resistance, and better electron capturing properties, as evidenced by electrochemical impedance spectroscopy and photoluminescence quenching. © 2021
  6. Keywords:
  7. Cyclic voltammetry ; Electrochemical impedance spectroscopy ; Etching ; Morphology ; Perovskite ; Perovskite solar cells ; Surface chemistry ; X ray photoelectron spectroscopy ; Bath treatment ; Device performance ; Electron transporting layer ; Fill-factor ; Interfacial treatments ; Lows-temperatures ; Performance ; Planar perovskite solar cell ; Surface-modification ; Water baths ; Temperature ; Electron ; Energy efficiency ; Film ; Inorganic compound ; Solar power
  8. Source: Solar Energy ; Volume 228 , 2021 , Pages 253-262 ; 0038092X (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S0038092X21008252