Research Article


2019, 12(1): 77–84


Surface molecular doping of all-inorganic perovskite using zethrenes molecules

Arramel1 (*), Hu Pan2, Aozhen Xie3,4,5, Songyan Hou3,4, Xinmao Yin1,6, Chi Sin Tang1,6,7, Nguyen T. Hoa3, Muhammad D. Birowosuto3, Hong Wang3,4, Cuong Dang3,4,5 (*), Andrivo Rusydi1,6,8, Andrew T. S. Wee1,9,10, and Jishan Wu2 (*)

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1 Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
2 Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
3 CINTRA UMI CNRS/NTU/THALES 3288, Research Techno Plaza, 50 Nanyang Drive, Level 6, Border X Block, Singapore 637553, Singapore
4 School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
5 Energy Research Institute @NTU (ERI@N), Nanyang Technological University, Research Techno Plaza, X-Frontier Block, Level 5, 50 Nanyang Drive, Singapore 637553, Singapore
6 Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 1176033, Singapore
7 NUS Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore, Singapore 117456, Singapore
8 NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore
9 Institute of Materials Research & Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
10 Centre for Advanced 2D Materials, National University of Singapore, Block S14, Level 6, 6 Science Drive 2, Singapore 117546, Singapore

Keywords: zethrene, photoelectron spectroscopy, perovskite, near edge X-ray absorption fine structure and molecular doping
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  • Abstract
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We present an optical and photoelectron spectroscopic study to elucidate the interfacial electronic properties of organic-inorganic semiconductor heterojunctions formed in a kinetically blocked heptazethrene triisopropylsilyl ethynylene (HZ-TIPS) and its homologue, octazethrene (OZ-TIPS) on an all-inorganic perovskite cesium lead bromide (CsPbBr3) surface. The photoluminescence behavior of the underlying perovskites upon differing molecular doping conditions was examined. It turns out that the charge transfer dynamics of thermally-evaporated OZ-TIPS molecule exhibited a faster average lifetime than that of the HZ-TIPS case suggesting the importance of the biradical state in the former molecule. An interfacial dipole was formed at the interface due to the competing interaction between the dispersion force of the bulky TIPS-substituent group and the attractive van der Waals interaction at the first few layers. Photoemission spectroscopy of the physisorbed HZ-TIPS shows chemical shifts, which indicates electron transfer from HZ-TIPS molecules to the CsPbBr3 perovskite single crystal. In contrast, the adsorbed OZ-TIPS molecular layer on CsPbBr3 demonstrates the opposite trend indicating a hole transfer process. The average molecular orientation as determined by near edge X-ray absorption fine structure (NEXAFS) suggests that the HZ-TIPS molecular plane is generally lifted with respect to the perovskite surface. We suggest that the nature of the closed-shell electronic ground state of HZ-TIPS could contribute to the formation of interfacial dipole at the molecule/perovskite interface.
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Surface molecular doping of all-inorganic perovskite using zethrenes molecules. Nano Res. 2019, 12(1): 77–84

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