LAKE WALES, Fla—A popular photovoltaic material called "perovskites" can rival graphene when grown in hybrid monolayers one atom thin, according to Department of Energy (DoE) funded researchers. This high energy material is easier to grow than graphene and can be doped to make the various varieties of ionic semiconductors needed to beat other two-dimensional (2-D) materials with tunable electronic/photonic properties.
"The high-quality 2D crystals exhibit efficient photoluminescence, and color tuning could be achieved by changing sheet thickness as well as composition via the synthesis of related materials," the researchers said in Science.
Perovskite with a pen for scale, collected by A.E. Foote from Magnet Cove, Arkansas for a mineral collection at Bringham Young University's Department of Geology, Provo, Utah. (Source: Bringham Young University)
The U.S. DoE's Office of Basic Energy Sciences funded the discovery with the help of its National Center for Electron Microscopy and Molecular Foundry (using a transmission electron microscopy and cathodoluminescence microscopy) and its Advanced Light Source (a grazing-incidence wide-angle x-ray scattering machine) at the DoE's Office of Science User Facilities and the National Institute for Health, using x-ray crystallography.
2-D nanomaterials are already the subject of intense research throughout the semiconductor industry because they mark the end-of-the-road in semiconductor scaling, being just a single atom thin. Also 2-D materials exhibit electronic properties that are unique and multiplied exponentially, in some cases, over thin-films just a few atomic layers thick.
As a result, the DoE decided to investigate the electronic properties of atomically thin hybrid organic-inorganic perovskite sheets as an easier-to-fabricate alternative to graphene and other more exotic material formulations. Since PVs are light sensitive, hybrid 2-D perovskites are not only a potential successor to silicon solar cells, according to the DoE, but could also be used in optoelectronic applications, such as photodetectors, light-emitting diodes and lasers.
Vacancy defects in an atomically thin monolayer can "dope" it to achieve desired electronic or photovoltaic properties. https://en.wikipedia.org/wiki/Monolayer#/media/File:MoS2_antisites%26vacancies.jpg
(Source: Jinhua Hong et. al.)
Scientists created these new forms of hybrid organic-inorganic perovskites in atomically thin 2D sheets and first showed how they hold promise as semiconductor materials for photovoltaic applications. Next they showed how they could serve as an alternative to other 2D semiconductors that are widely studied as potential successors to silicon in future electronic devices. In other words, hybrid organic-inorganic perovskite sheets could also stand-in for graphene, boron nitride, and molybdenum disulfide—all widely studied potential successors to silicon.
Grown at room temperature from solution its crystals measured about 10-microns. As they they relaxed during crystallization their band gap changed. By controlling the speed of crystallization, the DoE hopes to harness the changeable band gap property to control the color of emission, detection and other advanced electronic and photonic properties.
Scientists made a promising material for photovoltaics into atomically thin sheets that could be used both solar and many other electronic applications. The 2D hybrid perovskite sheets emit light (labeled as PL (photoluminescence) Intensity in the graph) whose color (wavelength) is tunable by changing sheet thickness and composition (i through vi).
Get all the details in Atomically thin two-dimensional organic-inorganic hybrid perovskites.
Besides the DoE, funding was also provided by the David and Lucile Packard Fellowship, the National Science Foundation the Alfred P. Sloan Research Fellowship, the Camille and Henry Dreyfus Foundation and the Suzhou Industrial Park.
— R. Colin Johnson, Advanced Technology Editor, EE Times