Double Charged Surface Layers in Lead Halide Perovskite Crystals

作者：Sarmah Smritakshi P; Burlakov Victor M; Yengel Emre; Murali Banavoth; Alarousu Erkki; El Zohry Ahmed M; Yang Chen; Alias Mohd S; Zhumekenov Ayan A; Saidaminov Makhsud I; Cho Namchul; Wehbe Nimer; Mitra Somak; Ajia Idris; Dey Sukumar; Mansour Ahmed E; Abdelsamie Maged; Amassian Aram; Roqan Iman S; Ooi Boon S; Goriely Alain; Bakr Osman M; Mohammed Omar F

来源：Nano Letters, 2017, 17(3): 2021-2027.

DOI：10.1021/acs.nanolett.7b00031

• Nanometer surface layers
• lead halide perovskite crystal
• one vs two-photon excitation
• ion migration
• defects

Understanding defect chemistry, particularly ion migration, and its significant effect on the surface's optical and electronic properties is one of the major challenges impeding the development of hybrid perovskite-based devices. Here, using both experimental and theoretical approaches, we demonstrated that the surface layers of the perovskite crystals may acquire a high concentration of positively charged vacancies with the complementary negatively charged halide ions pushed to the surface. This charge separation near the surface generates an electric field that can induce an increase of optical band gap in the surface layers relative to the bulk. We found that the charge separation, electric field, and the amplitude of shift in the bandgap strongly depend on the halides and organic moieties of perovskite crystals. Our findings reveal the peculiarity of surface effects that are currently limiting the applications of perovskite crystals and more importantly explain their origins, thus enabling viable surface passivation strategies to remediate them.

• 出版日期2017-3