Interfacial Dipole Layer Enables High-Performance Heterojunctions for Photoelectrochemical Water Splitting

Juwon Yun, Jeiwan Tan, Young Kwang Jung, Wooseok Yang, Hyungsoo Lee, Sunihl Ma, Young Sun Park, Chan Uk Lee, Wenzhe Niu, Jeongyoub Lee, Kyungmin Kim, S. David Tilley, Aron Walsh, Jooho Moon

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


TiO2has been widely used as an n-type overlayer, simultaneously serving as a protective layer for photocathodes. However, the photovoltage generated from a TiO2junction with p-type absorbers, such as p-Si, Sb2Se3, SnS, and Cu2O, is insufficient. We report a dipole reorientation strategy to overcome this limitation by inserting a polyethylenimine ethoxylated (PEIE) layer between a p-type absorber and TiO2. Furthermore, we demonstrate that the PEIE dipole orientation can be rearranged by increasing the layer thickness, leading to an upward shift of the TiO2band edge. The magnitude of band shift induced by the dipole effect depends on the TiO2layer thickness. Using this approach, the onset potential was significantly improved to 0.5 V versus the reversible hydrogen electrode (VRHE) in a p-Si/PEIE/TiO2/Pt device. The versatility of the effective dipole reorientation strategy was demonstrated by application to a range of TiO2-protected heterojunction photocathodes based on Sb2Se3, Cu2O, and SnS.

Original languageEnglish
Pages (from-to)1392-1402
Number of pages11
JournalACS Energy Letters
Issue number4
StatePublished - 8 Apr 2022

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