title: Intrinsic and Extrinsic Stability of Formamidinium Lead Bromide Perovskite Solar Cells Yielding High Photovoltage.
abstract: We report on both the intrinsic and the extrinsic stability of a formamidinium lead bromide [CH(NH2)2PbBr3= FAPbBr3] perovskite solar cell that yields a high photovoltage. The fabrication of FAPbBr3devices, displaying an outstanding photovoltage of 1.53 V and a power conversion efficiency of over 8%, was realized by modifying the mesoporous TiO2-FAPbBr3interface using lithium treatment. Reasons for improved photovoltaic performance were revealed by a combination of techniques, including photothermal deflection absorption spectroscopy (PDS), transient-photovoltage and charge-extraction analysis, and time-integrated and time-resolved photoluminescence. With lithium-treated TiO2films, PDS reveals that the TiO2-FAPbBr3interface exhibits low energetic disorder, and the emission dynamics showed that electron injection from the conduction band of FAPbBr3into that of mesoporous TiO2is faster than for the untreated scaffold. Moreover, compared to the device with pristine TiO2, the charge carrier recombination rate within a device based on lithium-treated TiO2film is 1 order of magnitude lower. Importantly, the operational stability of perovskites solar cells examined at a maximum power point revealed that the FAPbBr3material is intrinsically (under nitrogen) as well as extrinsically (in ambient conditions) stable, as the unsealed devices retained over 95% of the initial efficiency under continuous full sun illumination for 150 h in nitrogen and dry air and 80% in 60% relative humidity (T = ∼60 °C). The demonstration of high photovoltage, a record for FAPbBr3, together with robust stability renders our work of practical significance.
authors: Neha
authors: N
authors: Arora
authors: M Ibrahim
authors: MI
authors: Dar
authors: Cavendish Laboratory, Department of Physics, University of Cambridge , JJ Thomson Avenue, Cambridge, CB3 0HE United Kingdom.
authors: Mojtaba
authors: M
authors: Abdi-Jalebi
authors: Fabrizio
authors: F
authors: Giordano
authors: Max Planck Institute for Solid State Research , Heisenbergstraße 1, 70569 Stuttgart, Germany.
authors: Norman
authors: N
authors: Pellet
authors: Gwénolé
authors: G
authors: Jacopin
authors: Cavendish Laboratory, Department of Physics, University of Cambridge , JJ Thomson Avenue, Cambridge, CB3 0HE United Kingdom.
authors: Richard H
authors: RH
authors: Friend
authors: Shaik Mohammed
authors: SM
authors: Zakeeruddin
authors: Michael
authors: M
authors: Grätzel
keywords: Perovskite solar cells; charge recombination; interface passivation; mesoporous TiO2; photovoltage; stability