title: Crystal Engineering for Low Defect Density and High Efficiency Hybrid Chemical Vapor Deposition Grown Perovskite Solar Cells.
abstract: Synthesis of high quality perovskite absorber is a key factor in determining the performance of the solar cells. We demonstrate that hybrid chemical vapor deposition (HCVD) growth technique can provide high level of versatility and repeatability to ensure the optimal conditions for the growth of the perovskite films as well as potential for batch processing. It is found that the growth ambient and degree of crystallization of CH3NH3PbI3(MAPI) have strong impact on the defect density of MAPI. We demonstrate that HCVD process with slow postdeposition cooling rate can significantly reduce the density of shallow and deep traps in the MAPI due to enhanced material crystallization, while a mixed O2/N2carrier gas is effective in passivating both shallow and deep traps. By careful control of the perovskite growth process, a champion device with power conversion efficiency of 17.6% is achieved. Our work complements the existing theoretical studies on different types of trap states in MAPI and fills the gap on the theoretical analysis of the interaction between deep levels and oxygen. The experimental results are consistent with the theoretical predictions.
authors.affiliation: Department of Electronic and Information Engineering, The Hong Kong Polytechnic University , Hong Kong, P.R. China.
authors.forename: Annie
authors.initials: A
authors.lastname: Ng
authors.affiliation: Department of Electronic and Information Engineering, The Hong Kong Polytechnic University , Hong Kong, P.R. China.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Ren
authors.affiliation: Department of Electronic and Information Engineering, The Hong Kong Polytechnic University , Hong Kong, P.R. China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Shen
authors.affiliation: Department of Physics, Hong Kong Baptist University , Hong Kong, P.R. China.
authors.forename: Sin Hang
authors.initials: SH
authors.lastname: Cheung
authors.affiliation: Department of Electronic and Information Engineering, The Hong Kong Polytechnic University , Hong Kong, P.R. China.
authors.forename: Huseyin Cem
authors.initials: HC
authors.lastname: Gokkaya
authors.affiliation: Department of Physics, Hong Kong Baptist University , Hong Kong, P.R. China.
authors.forename: Shu Kong
authors.initials: SK
authors.lastname: So
authors.affiliation: Department of Physics, University of Hong Kong , Hong Kong, P.R. China.
authors.forename: Aleksandra B
authors.initials: AB
authors.lastname: Djurišić
authors.affiliation: Hefei National Laboratory of Physical Sciences at the Microscale, Synergetic Innovation Center of Quantum Information and Quantum Physics, CAS Key Laboratory of Materials for Energy Conversion, and Department of Materials Science and Engineering, University of Science and Technology of China , Hefei, Anhui 230000, P.R. China.
authors.forename: Yangyang
authors.initials: Y
authors.lastname: Wan
authors.affiliation: Hefei National Laboratory of Physical Sciences at the Microscale, Synergetic Innovation Center of Quantum Information and Quantum Physics, CAS Key Laboratory of Materials for Energy Conversion, and Department of Materials Science and Engineering, University of Science and Technology of China , Hefei, Anhui 230000, P.R. China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Wu
authors.affiliation: Department of Electronic and Information Engineering, The Hong Kong Polytechnic University , Hong Kong, P.R. China.
authors.forename: Charles
authors.initials: C
authors.lastname: Surya
keywords: cooling rates; crystallization; defects; growth ambient; hybrid chemical vapor deposition; passivation; perovskites; solar cells