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Interfacial Electron Transfer Barrier at Compact TiO 2 /CH 3 NH 3 PbI 3 Heterojunction
Author(s) -
Xing Guichuan,
Wu Bo,
Chen Shi,
Chua Julianto,
Yantara Natalia,
Mhaisalkar Subodh,
Mathews Nripan,
Sum Tze Chien
Publication year - 2015
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201403719
Subject(s) - materials science , heterojunction , optoelectronics , planar , electron transfer , photoluminescence , rectangular potential barrier , electron , hysteresis , nanotechnology , chemistry , photochemistry , computer science , physics , quantum mechanics , computer graphics (images)
Low‐temperature solution‐processed CH 3 NH 3 PbI 3 interfaced with TiO 2 has recently been demonstrated as a highly successful type‐II light harvesting heterojunction with ≈20% efficiency. Therefore, an efficient ultrafast photoexcited electron transfer from CH 3 NH 3 PbI 3 to TiO 2 is expected. However, by probing the photoexcited charge carrier dynamics in CH 3 NH 3 PbI 3 /quartz, CH 3 NH 3 PbI 3 /TiO 2 (compact), and CH 3 NH 3 PbI 3 /PCBM in a comparative study, an electron transfer potential barrier between CH 3 NH 3 PbI 3 and the compact TiO 2 (prepared with the spray pyrolysis method) formed by surface states is uncovered. Consequently, the CH 3 NH 3 PbI 3 photoluminescence intensity and lifetime is enhanced when interfaced to compact TiO 2 . The electron accumulation within CH 3 NH 3 PbI 3 needed to overcome this interfacial potential barrier results in the undesirable large current–voltage hysteresis observed for CH 3 NH 3 PbI 3 /TiO 2 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.