title: Interfacial Electron Transfer Barrier at Compact TiO2 /CH3 NH3 PbI3 Heterojunction.
abstract: Low-temperature solution-processed CH3 NH3 PbI3 interfaced with TiO2 has recently been demonstrated as a highly successful type-II light harvesting heterojunction with ≈20% efficiency. Therefore, an efficient ultrafast photoexcited electron transfer from CH3 NH3 PbI3 to TiO2 is expected. However, by probing the photoexcited charge carrier dynamics in CH3 NH3 PbI3 /quartz, CH3 NH3 PbI3 /TiO2 (compact), and CH3 NH3 PbI3 /PCBM in a comparative study, an electron transfer potential barrier between CH3 NH3 PbI3 and the compact TiO2 (prepared with the spray pyrolysis method) formed by surface states is uncovered. Consequently, the CH3 NH3 PbI3 photoluminescence intensity and lifetime is enhanced when interfaced to compact TiO2 . The electron accumulation within CH3 NH3 PbI3 needed to overcome this interfacial potential barrier results in the undesirable large current-voltage hysteresis observed for CH3 NH3 PbI3 /TiO2 planar heterojunctions. The findings in this study indicate that careful surface engineering to reduce this potential barrier is key to pushing perovskite solar cell efficiencies toward the theoretical limit.
authors.affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore.
authors.forename: Guichuan
authors.initials: G
authors.lastname: Xing
authors.affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore.
authors.forename: Bo
authors.initials: B
authors.lastname: Wu
authors.affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore.
authors.forename: Shi
authors.initials: S
authors.lastname: Chen
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore.|Energy Research Institute @NTU (ERI@N), Research Techno Plaza, X-Frontier Block, Level 5, 50 Nanyang Drive, Singapore, 637553, Singapore.
authors.forename: Julianto
authors.initials: J
authors.lastname: Chua
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore.|Energy Research Institute @NTU (ERI@N), Research Techno Plaza, X-Frontier Block, Level 5, 50 Nanyang Drive, Singapore, 637553, Singapore.
authors.forename: Natalia
authors.initials: N
authors.lastname: Yantara
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore.|Energy Research Institute @NTU (ERI@N), Research Techno Plaza, X-Frontier Block, Level 5, 50 Nanyang Drive, Singapore, 637553, Singapore.
authors.forename: Subodh
authors.initials: S
authors.lastname: Mhaisalkar
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798, Singapore.|Energy Research Institute @NTU (ERI@N), Research Techno Plaza, X-Frontier Block, Level 5, 50 Nanyang Drive, Singapore, 637553, Singapore.
authors.forename: Nripan
authors.initials: N
authors.lastname: Mathews
authors.affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore.
authors.forename: Tze Chien
authors.initials: TC
authors.lastname: Sum
keywords: CH3NH3PbI3; band bending; electron transfer; heterojunctions; hysteresis; interfacial barriers; ultrafast spectroscopy