Charge Trapping in Photovoltaically Active Perovskites and Related Halogenoplumbate Compounds.
Halogenoplumbate perovskites (MeNH3PbX3, where X is I and/or Br) have emerged as promising solar panel materials. Their limiting photovoltaic efficiency depends on charge localization and trapping processes that are presently insufficiently understood. We demonstrate that in halogenoplumbate materials the holes are trapped by organic cations (that deprotonate from their oxidized state) and Pb(2+) cations (as Pb(3+) centers), whereas the electrons are trapped by several Pb(2+) cations, forming diamagnetic lead clusters that also serve as color centers. In some cases, paramagnetic variants of these clusters can be observed. We suggest that charge separation in the halogenoplumbates resembles latent image formation in silver halide photography. Electron and hole trapping by lead clusters in extended dislocations in the bulk may be responsible for accumulation of trapped charge observed in this photovoltaic material.
†Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Ave, Argonne, Illinois 60439, United States.
Ilya A
IA
Shkrob
†Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Ave, Argonne, Illinois 60439, United States.|‡Chemistry Department, Benedictine University, 5700 College Road, Lisle, Illinois 60532, United States.
Timothy W
TW
Marin
charge transport and trapping; electron paramagnetic resonance; ionic liquids; perovskites; photovoltaic materials