Organic Cation Size-Dependent Defect Tolerance to Intolerance in “Hollow” Tin Perovskites

Abstract

Tin(II)-based hybrid halide perovskites suffer from intrinsic self-doping, yielding metallic-like dark conductivities that limit semiconductor applications. Building on our recent demonstration that ethylenediammonium incorporation into CH3NH3SnI3 suppresses carrier concentration via ionic compensation, we extend this strategy to 1,3-diammonium propane, 1,4-diammonium butane, and 1,5-diammonium pentane. Mechanochemical synthesis yields MA1–x(A)xSn1–0.7xI3–0.4x (x = 0.02–0.09) isostructural to α-CH3NH3SnI3, with solubility limited to x ≲ 0.10 and progressive microstrain broadening with cation size. All three substitutions reduce dark conductivity below 10 S m–1, indicating vacancy-mediated ionic compensation generalizes across the diammonium series. However, the real permittivity declines more steeply with x than the conductivity, which is consistent with the substitution-induced inhibition of (di)polar dynamics. Photocarrier mobility is greatly suppressed across all 3C–5C compositions, attributed to rapid trapping by structural disorder and vacancy-cation defect complexes absent from the intrinsic vacancy landscape. These results demonstrate that vacancy-mediated conductivity suppression and photocarrier dynamics are independently governed by cation identity.