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

Abstract

By applying amultitude of experimental techniques including

Fractional deviations in precursor stoichiometry dictate the properties, performance and stability of perovskite photovoltaic devices

“…While it is often claimed that iodine vacancies are the most abundant defects in perovskite films, 42,43 recent reports suggest that under non-equilibrium conditions (taking into account the growth conditions and precursor stoichiometry), iodine and MA interstitials and lead vacancies exhibit the smallest formation energies, especially at the surface. [44][45][46][47] We also note that recent experiments by Hawash et al showed that evaporating thin MAI layers on top of pristine perovskite films similarly results in an increase of the VB position of their samples.…”

Substrate-Dependent Photoconductivity Dynamics in a High-Efficiency Hybrid Perovskite Alloy

“…Many of these defects are mobile under the application of electric field and/or light, with iodine species and vacancies considered to be most mobile species. [14][15][16][17][18][19][20][21][22] Moreover, recent reports by Maier and coworkers show that the concentration of mobile iodine vacancies depends on illumination intensity. 19 This effect, which is expected from defect-energy calculations, 1,3,9 needs to be considered in addition to the established effects of light on charge motion and polarization when trying to understand light-related hysteresis phenomena.…”

“…19 This effect, which is expected from defect-energy calculations, 1,3,9 needs to be considered in addition to the established effects of light on charge motion and polarization when trying to understand light-related hysteresis phenomena. 15,20,[23][24][25][26][27][28][29] Here we study a high-performing material with precursor solution stoichiometry (FA 0.79 MA 0.16 Cs 0.05 ) 0.97 Pb(I 0.84 Br 0.16 ) 2. 97 (hereafter referred to as FAMACs) grown over four different substrates -TiO 2 , SnO 2 , ITO, and NiO.…”

Short-range ion dynamics in methylammonium lead iodide by multinuclear solid state NMR and127I NQR

“…[6][7][8] In addition, the interaction of the organic cations with the inorganic framework through hydrogen bonding 9 has been suggested to contribute to the stabilization of the structure, 10 while also influencing the optical and electronic properties of the materials. 11,12 Therefore, the goal of the present study is to probe such short-range ion dynamics in the archetypal halide perovskite MAPbI 3 via solid-state NMR ( 1 H, 13 C, 14 N, 15 N and 207 Pb) and Nuclear Quadrupolar Resonance ( 127 I NQR), with particular attention to the rotational motion of the methylammonium (MA) cation, as well as to the interaction between MA and the inorganic lattice. Long-range ion dynamics, that gives rise to a significant iodine conductivity in MAPbI 3 , was studied by our group in a previous work.…”

“…Long-range ion dynamics, that gives rise to a significant iodine conductivity in MAPbI 3 , was studied by our group in a previous work. 13 Owing to its unsurpassed sensitivity to short-range interactions, NMR spectroscopy is very effective to study dynamic processes, [14][15][16][17][18] and its first applications to the investigation of halide perovskites go back as early as 1985. [19][20][21][22] In these studies, reorientation of the organic moiety was observed in all crystalline phases of MAPbI 3 (but also MAPbBr 3 and MAPbCl 3 ) through 1 H, 2 H and 14 N spinlattice relaxation times (T 1 ) measurements.…”