The Nature of Ion Conduction in Methylammonium Lead Iodide: A Multimethod Approach

Abstract

By applying a multitude of experimental techniques including 1H, 14N, 207Pb NMR and 127I NMR/NQR, tracer diffusion, reaction cell and doping experiments, as well as stoichiometric variation, conductivity, and polarization experiments, iodine ions are unambiguously shown to be the mobile species in CH3NH3PbI3, with iodine vacancies shown to represent the mechanistic centers under equilibrium conditions. Pb2+ and CH3NH3 + ions do not significantly contribute to the long range transport (upper limits for their contributions are given), whereby the latter exhibit substantial local motion. The decisive electronic contribution to the mixed conductivity in the experimental window stems from electron holes. As holes can be associated with iodine orbitals, local variations of the iodine stoichiometry may be fast and enable light effects on ion transport.

Achieving Long‐Term Operational Stability of Perovskite Solar Cells with a Stabilized Efficiency Exceeding 20% after 1000 h

“…[1] Despite such high PCEs, poor long-term stability of mp-TiO 2 based PSCs is a problematic issue for commercialization. [14,15] It has also been demonstrated that oxygen induces photodegradation of methylammonium lead iodide (MAPbI 3 ). [13] The long-term operational stability of 1000 h in BaSnO 3 -based PSCs was realized only in a laminate cell.…”

Control over Self‐Doping in High Band Gap Perovskite Films

“…Since the distance between the HaP incorporated in the TiO 2 and the TiO 2 nanoparticles is very small, more strongly doped materials such as MAPbBr 3 (Cl) and CsPbBr 3 should have a stronger net electric field compared to the more intrinsic materials (MAPbBr 3 , (FA,MA,Cs)PbBr 3 ). [39,40] If these two properties, alone or together, are the ones that are responsible for the observed hysteresis in MAPbI 3 -based devices [and in (FA,MA,Cs)PbBr 3 as seen in Figure 1], it can indicate that ion migration is more dominant in the mixed cation layers than in the single cation devices, possibly because of a less closely packed lattice in the former (where a c = 6.00 Å) than in the MAPbBr 3 (cf. To visualize this, we plot in Figure 4 the normalized EBIC collection efficiency versus the mp-TiO 2 \HaP area for the four different HaP devices that were considered in Figure 2.…”

Tracking Dynamic Phase Segregation in Mixed‐Halide Perovskite Single Crystals under Two‐Photon Scanning Laser Illumination

“…Optoelectronic properties of perovskites, including large absorption coefficient, long diffusion length, long carrier lifetimes, and high tolerance of defects, have been confirmed to influence halide‐based perovskite device performance . Since perovskite is a mixed carrier‐ionic conductor, perovskite‐based devices are significantly affected by the dynamics of mobile ions . Mixed‐halide perovskites with tunable bandgaps enable bandgap engineering in tandem solar cells and multiple‐color LED .…”