PL emission mapping of MA0.17FA0.83Pb(I0.5Br0.5)3 at the detection wavelength of 670 nm and 790 nm after local illumination for 1 h with a beam size of ~ 1 mm and density of 1 sun on the bare film, and over an annular aperture with a 1 mm diameter pinhole and a center obstruction target of 850 µm, respectively.
CREDIT: by Xiaoxiao Sun, Yong Zhang, Weikun Ge
Lead halide perovskites (e.g., MAPbI3) are an emerging family of semiconductor materials with excellent optoelectronic properties ideally suited for photovoltaic and light-emitting applications.
Significant ion migration has been reported in these materials and is one of the main mechanisms responsible for anomalous I-V hysteresis and poor stability in the perovskite solar cells. Particularly, mixed halide perovskites further exhibit photoinduced halide anion “segregation” under continuous above-bandgap illumination, and the process is reversible when the illumination is removed. This segregation phenomenon is commonly viewed as an adverse effect to the optoelectronic applications and should be suppressed. The most observed effect of the ion segregation is the red shift in photoluminescence (PL) peak from the expected wavelength for the alloy to that of a significantly higher composition of Iodine. It is generally asserted that a uniform alloy MAPbI1-xBrx would segregate into Iodine-rich and Bromine-rich domains within the illuminated area.
A number of microscopic mechanisms have been proposed to explain the phenomenon. However, none of them can unambiguously explain all the key aspects of the phenomenon. In fact, the chemical and structural characteristics of the so called “Br-rich” and “I-rich” regions are not yet well understood, although they are implicitly assumed to be simply Br-rich and I-rich alloys, respectively.
In a new paper published in Light Science & Application by scientists from Empa?Swiss Federal Laboratories for Materials Science and Technology, Switzerland, The University of North Carolina at Charlotte, USA, and Tsinghua University, China have discovered that the anion segregation in the mixed halide alloy is a nonlocal effect of which the ion redistribution may occur in a macroscopic or mesoscopic scale far beyond the illuminated area in a scale proportional to the illumination beam size, up to well over mm. This work offers a completely new perspective to the generally assumed photo-induced “on-site” anion segregation in mixed halide perovskite alloys.
The authors mentioned “Specifically, we find that under illumination, within the illumination area, the PL peak is red shifted from the initial position; while concurrently, outside the illuminated area, the alloy PL peak is strongly enhanced in a ring area circling the illuminated area. Furthermore, the process is reversible, but non-monotonically, exhibiting ultra-low-frequency damped oscillations between the ring and center in terms of PL intensity and position.”
“These surprising observations can be explained as that free Br ions are expelled from the illuminated area, resulting in a positively charged area, and concomitantly forming a negatively charged Br-rich ring, both being off stoichiometry from the original alloy. This phenomenon can be viewed as an ionic analogy of a mesoscopic PL ring formation away from the illuminated site in GaAs/AlGaAs quantum wells, resulting from the disparity in the electron and hole diffusion lengths and thus their spatial profiles”, they added.
The authors suggest that the peculiar oscillatory behavior could reflect an oscillation of ionic plasma or ionic plasmon, which has not been reported in solids. Besides the broader implications beyond the field of the halide perovskites, these findings offer new insights into the underlying mechanism of the ion segregation in the mixed halide alloys, which makes it not necessarily an adverse phenomenon to suppress but something potentially useful, e.g., for energy storage. As a promising demonstration, a voltage around 0.4 V being measured between the center and ring, pointing to the possibility of a battery that can be directly charged by light.
The Latest Updates from Bing News
Go deeper with Bing News on:
- Metro’s battery-powered buses come in a new, shocking palette
Hundreds of new battery-powered buses are expected to arrive on King County Streets between 2025 and 2035. They'll come with a new color scheme.
- New Battery Health Features Remain Limited to iPhone 15 Models on First iOS 17.1 Beta
All four iPhone 15 models have two new battery health features in the Settings app, including the ability to view the battery's cycle count ...
- Specialized's all-new Creo 2 is a battery-powered, gravel-devouring beast
Its precursor, the Specialized Turbo Creo SL, was an innovative machine. An all-electric, road-biased bike with a beautifully integrated electric propulsion system and the ability to venture off the ...
- Soelect launches institute for training workers for new-technology battery industry
So on Tuesday, Soelect, with the help of another green-technology enthusiast, North Carolina Gov. Roy Cooper, announced the launch of the Carolina Battery Institute, a non-profit organization intended ...
- A new battery recycling facility will deepen Kentucky's ties to the electric vehicle sector
A recycling facility will be built in Kentucky to shred electric vehicle batteries in a $65 million venture between American and South Korean companies that will supply material for a separate battery ...
Go deeper with Bing News on:
Light charged battery
- MilliMobile is a tiny, self-driving robot powered only by light and radio waves
Small mobile robots carrying sensors could perform tasks like catching gas leaks or tracking warehouse inventory. But moving robots demands a lot of energy, and batteries, the typical power source, ...
- 4,000-lumen Guard X bike light changes colors and thwarts thieves
While there are now a ton of high-tech bike headlights on the market, most of them are pretty similar to one another. The Guard X stands out, however, with features like an anti-theft alarm, ...
- Here's what all those dashboard warning lights mean
And the fact you're not moving anywhere, of course. When you're warned you've got low battery, that's the time to charge. Cut it too fine and you might see this little fella light up. This ...
- Convergent Energy and Power Partners with West Boylston Municipal Light Plant to Provide Cost-Reducing Battery Storage System
Convergent Energy and Power (Convergent), a leading provider of energy storage solutions in North America, announced today its plans to provide Massachusetts’s municipally-owned utility company West ...
- RWE gives green light for utility-scale battery storage project in the Netherlands
Highlights 35 MW storage systems to be installed at RWE biomass plant in Eemshaven Battery storage to be virtually coupled with RWE power plants in the Netherlands RWE to invest approxim. . .