Dynamical Imaging of Surface Photopotentials in Hybrid Lead Iodide Perovskite Films under High Optical Irradiance and the Role of Selective Contacts. Issue 16 (9th June 2020)

• Record Type: Journal Article
• Authors: Pietralunga, Silvia Maria; Irde, Gabriele; Barker, Alex J.; Ball, James M.; Petrozza, Annamaria; Sala, Vittorio; Zani, Maurizio; Lanzani, Guglielmo; Tagliaferri, Alberto
• Is Part Of: Advanced materials interfaces. Volume 7:Issue 16(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-06-09
• Subjects: concentrated photovoltaics -- high optical irradiance -- hybrid lead‐halide perovskites -- surface polarization -- time‐resolved SEM; Materials science -- Periodicals; 620.11
• DOI: 10.1002/admi.202000297
• Languages: English
• ISSNs: 2196-7350

Abstract

Abstract: To leverage the outstanding photonic qualities of lead halide hybrid perovskites under high optical irradiance, their reliability and temporal stability must be assessed. Time‐resolved scanning electron microscopy unveils that when illuminating the free surface of methylammonium lead iodide (MAPbI3 ) films at 500 Sun in vacuum, a giant photopotential locally develops in tens of seconds, differently evolving depending on charge‐selective substrates. It is reversible on timescales of minutes in the case of hole‐transporting poly(3, 4‐ethylenedioxythiophene) polystyrene sulfonate, while more persistent effects occurs, on the timescale of hours, in the case of electron‐transporting TiO2 . In addition, films grown on TiO2 show irreversible decay of photoluminescence measured in situ and photoinduced alteration of the work function at some grain boundaries. Different responses at high irradiance are ascribable to contact‐dependent and light‐induced spatial redistribution of charged defects, either ions or localized dipoles. It is also clear that photoexcited charges play different roles in the photochemistry of systems, depending on selective contacts and they are likely to mediate diverse photoassisted redox reaction paths. The TiO2 layer may act as a photocatalyst, leading to MAPbI3 degradation and to irreversible polarization, which will hinder high‐irradiance applications. Abstract : Illumination of MAPbI3 thin films at 500 Sun may induce giant photopotentials at the free film surface. Their recovery dynamics crucially depends on the nature of selective contact at substrate. TiO2 contacts issue a permanent surface polarization effect, also suggesting a role of TiO2 as a catalyst for photoassisted redox reaction paths ultimately causing local degradation of the perovskite operated under high irradiance.