Suppressing\nHalide Segregation in Wide-Band-Gap Mixed-Halide\nPerovskite Layers through Post-Hot Pressing

Abstract

Mixed-halide\nperovskites (MHPs) have attracted attention as suitable\nwide-band-gap candidate materials for tandem applications owing to\ntheir facile band-gap tuning. However, when smaller bromide ions are\nincorporated into iodides to tune the band gap, photoinduced halide\nsegregation occurs, which leads to voltage deficit and photoinstability.\nHere, we propose an original post-hot pressing (PHP) treatment that\nsuppresses halide segregation in MHPs with a band gap of 2.0 eV. The\nPHP treatment reconstructs open-structured grain boundaries (GBs)\nas compact GBs through constrained grain growth in the in-plane direction,\nresulting in the inhibition of defect-mediated ion migration in GBs.\nThe PHP-treated wide-band-gap (2.0 eV) MHP solar cells showed a high\nefficiency of over 11%, achieving an open-circuit voltage (<i>V</i>_oc) of 1.35 V and improving the maintenance\nof the initial efficiency under the working condition at AM 1.5G.\nThe results reveal that the management of GBs is necessary to secure\nthe stability of wide-band-gap MHP devices in terms of halide segregation.