Understanding the Space-Charge Layer in SnO2for Enhanced Electron Extraction in Hybrid Perovskite Solar Cells

Sarah Su O. Youn, Jihyun Kim, Junhong Na, William Jo, Gee Yeong Kim

Research output: Contribution to journalArticlepeer-review


Tin oxide (SnO2) has been widely used as an n-type metal oxide electron transport layer in perovskite solar cells (PSCs) owing to its superior electrical and optical properties and low-temperature synthesis process. In particular, the interfacial effect between indium tin oxide (ITO) and SnO2is an important parameter that controls the charge transport properties and device performance of the PSCs. Therefore, understanding the interfacial effect of ITO/SnO2and its role in PSCs is crucial, but it is not studied intensively. Herein, we investigated the space-charge effect at the interface of ITO/SnO2using transfer length measurement and conductive atomic force microscopy as a function of SnO2thickness. Moreover, optical, morphologic, and device measurements were performed to determine the optimal SnO2thickness for PSCs. The space-charge effect was identified in ITO/SnO2when the SnO2layer was very thin due to electron depletion near the interface. Interestingly, a critical kink point was observed at approximately 10 nm SnO2thickness, indicating the electron depletion and weak charge transfer behavior of the device. Thus, a thickness around 20 nm was favorable for the best PSC performance because charge transport behavior in the thin SnO2layer was depressed by electron depletion. However, when the thickness of SnO2exceeded 50 nm, the device performance deteriorated due to increased series resistance. This study provides a strategy to tune the electron transport layer and boost the charge transport behavior in PSCs, making important contributions to optimizing SnO2-based PSCs.

Original languageEnglish
Pages (from-to)48229-48239
Number of pages11
JournalACS Applied Materials and Interfaces
Issue number42
StatePublished - 26 Oct 2022


  • electron depletion
  • interface
  • ITO
  • lead halide perovskite
  • perovskite solar cell
  • SnO
  • space-charge layer


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