title: Influence of void-free perovskite capping layer on the charge recombination process in high performance CH3NH3PbI3 perovskite solar cells.
abstract: The stunning rise of methylammonium lead iodide perovskite material as a light harvesting material in recent years has drawn much attention in the photovoltaic community. Here, we investigated in detail the uniform and void-free perovskite capping layer in the mesoscopic perovskite devices and found it to play a critical role in determining device performance and charge recombination process. Compared to the rough surface with voids of the perovskite layer, surface of the perovskite capping layer obtained from sequential deposition process is much more uniform with less void formation and distribution within the TiO2 mesoscopic scaffold is more homogeneous, leading to much improved photovoltaic parameters of the devices. The impact of void free perovskite capping layer surface on the charge recombination processes within the mesoscopic perovskite solar cells is further scrutinized via charge extraction measurement. Modulation of precursor solution concentrations in order to further improve the perovskite layer surface morphology leads to higher efficiency and lower charge recombination rates. Inhibited charge recombination in these solar cells also matches with the higher charge density and slower photovoltage decay profiles measured.
authors.affiliation: Energy Research Institute @ NTU (ERI@N), Nanyang Technological University, Research Techno Plaza, 50 Nanyang Drive, 637553, Singapore and School of Materials Science and Engineering, Nanyang Technological University, Block N4.1, 50 Nanyang Avenue, 639798, Singapore. nripan@ntu.edu.sg lydiawong@ntu.edu.sg.
authors.forename: Kunwu
authors.initials: K
authors.lastname: Fu
authors.affiliation: Singapore-Berkeley Research Initiative for Sustainable Energy, 1 Create Way, 138602, Singapore and Molecular Foundry at Lawrence Berkeley National Laboratory, One Cyclotron Rd, NCEM Bldg. 72, University of California Berkeley, California 94720, USA.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Nelson
authors.affiliation: Singapore-Berkeley Research Initiative for Sustainable Energy, 1 Create Way, 138602, Singapore and Molecular Foundry at Lawrence Berkeley National Laboratory, One Cyclotron Rd, NCEM Bldg. 72, University of California Berkeley, California 94720, USA.
authors.forename: Mary Cooper
authors.initials: MC
authors.lastname: Scott
authors.affiliation: Singapore-Berkeley Research Initiative for Sustainable Energy, 1 Create Way, 138602, Singapore and Molecular Foundry at Lawrence Berkeley National Laboratory, One Cyclotron Rd, NCEM Bldg. 72, University of California Berkeley, California 94720, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Minor
authors.affiliation: Energy Research Institute @ NTU (ERI@N), Nanyang Technological University, Research Techno Plaza, 50 Nanyang Drive, 637553, Singapore and School of Materials Science and Engineering, Nanyang Technological University, Block N4.1, 50 Nanyang Avenue, 639798, Singapore. nripan@ntu.edu.sg lydiawong@ntu.edu.sg and Singapore-Berkeley Research Initiative for Sustainable Energy, 1 Create Way, 138602, Singapore.
authors.forename: Nripan
authors.initials: N
authors.lastname: Mathews
authors.affiliation: Energy Research Institute @ NTU (ERI@N), Nanyang Technological University, Research Techno Plaza, 50 Nanyang Drive, 637553, Singapore and School of Materials Science and Engineering, Nanyang Technological University, Block N4.1, 50 Nanyang Avenue, 639798, Singapore. nripan@ntu.edu.sg lydiawong@ntu.edu.sg.
authors.forename: Lydia Helena
authors.initials: LH
authors.lastname: Wong