Influence of Organic-Cation Defects on Optoelectronic Properties of ASnI 3 Perovskites A=HC(NH 2 ) 2 , CH 3 NH 3 .

Tin organic-inorganic halide perovskites (tin OIHPs) possess a desirable band gap and their power conversion efficiency (PCE) has reached 14 %. A commonly held view is that the organic cations in tin OIHPs would have little impact on the optoelectronic properties. Herein, we show that the defective organic cations with randomly dynamic characteristics can have marked effect on optoelectronic properties of the tin OIHPs. Hydrogen vacancies originated from the proton dissociation from FA [HC(NH 2 ) 2 ] in FASnI 3 can induce deep transition levels in the band gap but yield relatively small nonradiative recombination coefficients of 10 -15  cm 3  s -1 , whereas those from MA (CH 3 NH 3 ) in MASnI 3 can yield much larger nonradiative recombination coefficients of 10 -11  cm 3  s -1 . Additional insight into the "defect tolerance" is gained by disentangling the correlations between dynamic rotation of organic cations and charge-carrier dynamics.