Diffusion Enhancement in Highly Excited MAPbI₃ Perovskite Layers with Additives

Abstract

Carrier mobility is one of the crucial parameters determining the electronic device performance. We apply the light-induced transient grating technique to measure independently the carrier diffusion coefficient and lifetime, and to reveal the impact of additives on carrier transport properties in wet-cast CHNHPbI (MAPbI) perovskite films. We use the high excitation regime, where diffusion length of carriers is controlled purely by carrier diffusion and not by the lifetime. We demonstrate a four-fold increase in diffusion coefficient due to the reduction of localization center density by additives; however, the density dependence analysis shows the dominance of localization-limited diffusion regime. The presented approach allows us to estimate the limits of technological improvement-carrier diffusion coefficient in wet-cast layers can be expected to be enhanced by up to one order of magnitude.

Interface limited hole extraction from methylammonium lead iodide films

“…This shows that charge carriers could be extracted about twice as fast given the interfacial transfer rate was much faster. The high value of the diffusion coefficient is close to the values reported in single crystals 6 suggesting that film quality does not suffer much because of using a solution processing method rather than a more complicated single crystal growth method.…”

“…Many attempts at measuring and enhancing charge transport in the most popular perovskite, CH 3 NH 3 PbI 3 (MAPbI 3 or MAPI) have been published in the literature. [3][4][5][6] The reported values of the charge diffusion coefficient in solution processed MAPbI 3 films range from B10 À5 to 2.7 cm 2 s À1 spanning five orders of magnitude. 6 This can be partly explained by different material properties of the same stoichiometry perovskites depending on the synthesis, deposition method, post processing and substrate choice, but in addition different measurement techniques and experiment conditions can give different results.…”

“…[3][4][5][6] The reported values of the charge diffusion coefficient in solution processed MAPbI 3 films range from B10 À5 to 2.7 cm 2 s À1 spanning five orders of magnitude. 6 This can be partly explained by different material properties of the same stoichiometry perovskites depending on the synthesis, deposition method, post processing and substrate choice, but in addition different measurement techniques and experiment conditions can give different results. Transient grating technique has revealed weak dependence of the ambipolar carrier diffusion coefficient on carrier density in perovskites of high compositional quality whilst other films showed very strong dependence on carrier density which was attributed to trap filling.…”

Radiative Efficiency and Charge‐Carrier Lifetimes and Diffusion Length in Polycrystalline CdSeTe Heterostructures

“…Similar GB effects were reported for perovskites . Impact of carrier localization to D e reduction is also not excluded . Regardless of uncertainty in scattering mechanisms, we find comparable D e and μ in polycrystalline CdSe 0.2 Te 0.8 DHs and in CdTe single crystals, which indicates the low density of scattering centers.…”

Lack of Photon Antibunching Supports Supertrap Model of Photoluminescence Blinking in Perovskite Sub‐Micrometer Crystals

“…Note that inhomogeneity of PL spectrum of MAPbI 3 at room temperature was reported in some publications and was associated with a radiative recombination of shallowly trapped charges. [ 49 ] We did not observe this effect in our samples or at least the contribution of this emission (if it existed in our samples at all) did not change during the PL intensity fluctuations.…”