Close

Search

Search Menu
Photonics Media Photonics Buyers' Guide Photonics Spectra BioPhotonics EuroPhotonics Vision Spectra Photonics Showcase Photonics ProdSpec Photonics Handbook
More News

Improving the Stability and Optical Properties of Perovskite Films

Facebook Twitter LinkedIn Email Comments
HONG KONG, Feb. 14, 2019 — A new approach to producing all-inorganic perovskite films — the result of a joint research effort by City University of Hong Kong (CityU) and Shanghai University — could further the development of high-color-purity, low-cost perovskite LEDs with a high operational lifetime.

The researchers developed an efficient fabrication approach leading to dense, smooth, pinhole-free CsPbBr3 perovskite films with high thermal stability. They introduced trifluoroacetate (TFA) anions to passivate surface defects and control the crystal growth. The interaction of the TFA anions with Pb2+ cations in a CsPbX3 precursor solution significantly improved the crystallization rate of the perovskite films and suppressed surface defects. Using cesium TFA as the cesium source in the one-step solution coating, instead of the commonly used cesium bromide (CsBr), enabled fast crystallization of small-grained CsPbBr3 perovskite crystals, leading to the formation of smooth and pinhole-free perovskite films.

Improving the stability and optical properties of perovskites films, City University of Hong Kong.

a) Device structure and a corresponding cross-sectional TEM image of the multilayer PeLEDs; b) schematic flat-band energy diagram of the PeLED; c) normalized photoluminescence spectrum of the CsPbBr3 film, and electroluminescence spectrum of the PeLED at an applied voltage of 5.5 V. Courtesy of the City University of Hong Kong.

The result was efficient, stable, green perovskite LEDs (PeLEDs) based on inorganic perovskite films, with a high current efficiency of 32.0 cd A-1, corresponding to an external quantum efficiency of 10.5 percent. According to the researchers, their all-inorganic perovskite LEDs demonstrated a record operational lifetime, with a half-lifetime of over 250 hours at an initial luminance of 100 cd/m−2 — a 17 times improvement in operational lifetime compared with CsBr-derived PeLEDs.

PeLEDs potentially offer low manufacturing costs, high-quality light, and energy efficiency. Metal halide (that is, compounds of metals with chlorine, bromine, or iodine) perovskites are a potentially valuable material for solution-processed LEDs, owing to optical properties that include saturated emission colors and easy color tunability.

The researchers say that perovskites based on inorganic cesium cations exhibit better thermal and chemical stability compared to organic-inorganic “hybrid” metal halide perovskites, and could provide the basis for high-performance LEDs with reasonable operational stability. They said that previous inorganic PeLEDs have exhibited relatively poor electroluminescence performance due to their large perovskite grain sizes.

“Our study suggests that the high color purity and low-cost all-inorganic lead halide perovskite films can be developed into highly efficient and stable LEDs via a simple optimization of the grain boundaries,” said professor Andrey Rogach at CityU. “I foresee significant application potential of such films, as they are easy to fabricate and can be easily deposited by printing to realize various optoelectronic devices.”

The research was published in Nature Communications (https://doi.org/10.1038/s41467-019-08425-5). 

Photonics.com
Feb 2019
GLOSSARY
optoelectronics
A sub-field of photonics that pertains to an electronic device that responds to optical power, emits or modifies optical radiation, or utilizes optical radiation for its internal operation. Any device that functions as an electrical-to-optical or optical-to-electrical transducer. Electro-optic often is used erroneously as a synonym.
Research & TechnologyeducationAsia-PacificCity University of Hong KongShanghai UniversityLEDslight sourcesmaterialsopticsoptical propertiesoptoelectronicsphotovoltaicsConsumerenergyenvironmentnanonanoscale materialsperovskitesall-inorganic perovskites

Comments
back to top
Facebook Twitter Instagram LinkedIn YouTube RSS
©2019 Photonics Media, 100 West St., Pittsfield, MA, 01201 USA, info@photonics.com

Photonics Media, Laurin Publishing
x We deliver – right to your inbox. Subscribe FREE to our newsletters.
We use cookies to improve user experience and analyze our website traffic as stated in our Privacy Policy. By using this website, you agree to the use of cookies unless you have disabled them.