Mobile Charge-Induced Fluorescence Intermittency in Methylammonium Lead Bromide Perovskite

Abstract

Organic-inorganic halide perovskite has emerged as a very promising material for solar cells due to its excellent photovoltaic enabling properties resulting in rapid increase in device efficiency over the last 3 years. Extensive knowledge and in-depth physical understanding in the excited state carrier dynamics are urgently required. Here we investigate the fluorescence intermittency (also known as blinking) in vapor-assisted fabricated CH3NH3PbBr3 perovskite. The evident fluorescence blinking is observed in a dense CH3NH3PbBr3 perovskite film that is composed of nanoparticles in close contact with each other. In the case of an isolated nanoparticle no fluorescence blinking is observed. The "ON" probability of fluorescence is dependent on the excitation intensity and exhibits a similar power rule to semiconductor quantum dots at higher excitation intensity. As the vapor-assisted fabricated CH3NH3PbBr3 perovskite film is a cluster of nanoparticles forming a dense film, it facilitates mobile charge migration between the nanoparticles and charge accumulation at the surface or at the boundary of the nanoparticles. This leads to enhanced Auger-like nonradiative recombination contributing to the fluorescence intermittency observed. This finding provides unique insight into the charge accumulation and migration and thus is of crucial importance for device design and improvement.

Triggering the Passivation Effect of Potassium Doping in Mixed‐Cation Mixed‐Halide Perovskite by Light Illumination

“…Figure 2 compares the consecutive FLIM images of 0 and 3.5 mol% K + perovskites to investigate the impact of light soaking, covering the time periods from the initial dark, bias light ON, and light OFF for recovery. [26,27] In contrast, the 3.5 mol% K + perovskite film exhibits a monotonic PL enhancement, ascribed to defect curing during light soaking. During light soaking (Stage 2), the dominant phenomena include the quenching effect of mobile ions activated by light illumination, and an enhancement effect due to defect curing.…”

“…[17] When covered by Spiro, efficient hole extraction dominates the carrier recombination and therefore significantly shortens the PL lifetime, [25] thus the grain morphologies are distinguishable in the FLIM images with grain sizes matching the SEM images ( Figure S1, Supporting Information). [26][27][28][29] The variations of PL intensity and PL lifetime depend on the competition between these effects. The scanning images of PL intensity (Figure 2a In the pre-illumination stage (Stage 1), PL intensities obtained from both 0 and 3.5 mol% K + perovskite films are homogeneously distributed over the whole detected area, as in Figure 1c,e.…”

Impact of Structural Dynamics on the Optical Properties of Methylammonium Lead Iodide Perovskites

“…[53,65,[84][85][86] Wen et al [86] fabricated CH 3 NH 3 PbBr 3 perovskite nanoparticles (NP) and films to investigate the PL blinking properties. In isolated CH 3 NH 3 PbBr 3 nanoparticles, there is no observation of PL blinking.…”

Different emissive states in the bulk and at the surface of methylammonium lead bromide perovskite revealed by two-photon micro-spectroscopy and lifetime measurements

“…It is often assumed that the PL is solely due to the radiative recombination of free carriers at the band-edge, and the reported lifetime of this recombination processes from sub-nanosecond to hundreds of nanoseconds. [18][19][20][21] Stranks et al 5 have used a general model including free carriers, excitons, and subgap states to describe the time traces of PL assuming that the PL from excitons (binding energy of about 15 meV) and free carriers at room temperature are indistinguishable. However, the PL spectrum at room temperature is rather broad, and Wehrenfennig et al 18 have considered the possible contribution of polaronic effects or "self-trapping" in the broadening of the spectrum.…”