title: Amino-Acid-Induced Preferential Orientation of Perovskite Crystals for Enhancing Interfacial Charge Transfer and Photovoltaic Performance.
abstract: Interfacial engineering of perovskite solar cells (PSCs) is attracting intensive attention owing to the charge transfer efficiency at an interface, which greatly influences the photovoltaic performance. This study demonstrates the modification of a TiO2electron-transporting layer with various amino acids, which affects charge transfer efficiency at the TiO2/CH3NH3PbI3interface in PSC, among which the l-alanine-modified cell exhibits the best power conversion efficiency with 30% enhancement. This study also shows that the (110) plane of perovskite crystallites tends to align in the direction perpendicular to the amino-acid-modified TiO2as observed in grazing-incidence wide-angle X-ray scattering of thin CH3NH3PbI3perovskite film. Electrochemical impedance spectroscopy reveals less charge transfer resistance at the TiO2/CH3NH3PbI3interface after being modified with amino acids, which is also supported by the lower intensity of steady-state photoluminescence (PL) and the reduced PL lifetime of perovskite. In addition, based on the PL measurement with excitation from different side of the sample, amino-acid-modified samples show less surface trapping effect compared to the sample without modification, which may also facilitate charge transfer efficiency at the interface. The results suggest that appropriate orientation of perovskite crystallites at the interface and trap-passivation are the niche for better photovoltaic performance.
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University, Taipei, 10617, Taiwan.|Center for Condensed Matter Sciences, National Taiwan University, Taipei, 10617, Taiwan.
authors.forename: Yen-Chen
authors.initials: YC
authors.lastname: Shih
authors.affiliation: Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, 10617, Taiwan.
authors.forename: Yu-Bing
authors.initials: YB
authors.lastname: Lan
authors.affiliation: Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, 10617, Taiwan.|Department of Electrical Engineering, National Taiwan University, Taipei, 10617, Taiwan.
authors.forename: Chia-Shuo
authors.initials: CS
authors.lastname: Li
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University, Taipei, 10617, Taiwan.|Center for Condensed Matter Sciences, National Taiwan University, Taipei, 10617, Taiwan.|Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan.
authors.forename: Hsiao-Chi
authors.initials: HC
authors.lastname: Hsieh
authors.affiliation: Center for Condensed Matter Sciences, National Taiwan University, Taipei, 10617, Taiwan.
authors.forename: Leeyih
authors.initials: L
authors.lastname: Wang
authors.affiliation: Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, 10617, Taiwan.|Department of Electrical Engineering, National Taiwan University, Taipei, 10617, Taiwan.
authors.forename: Chih-I
authors.initials: CI
authors.lastname: Wu
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University, Taipei, 10617, Taiwan.
authors.forename: King-Fu
authors.identifier: 0000-0002-4187-9424
authors.initials: KF
authors.lastname: Lin
keywords: GIWAXS; amino acids; charge transfer; crystalline orientation; perovskite solar cells