Researchers at Universitat Jaume I (UJI) have shown that new semiconductor nanoplatelets synthesized in laboratories can improve the brightness of LEDs, lasers and LCD screens of computers or televisions because they allow to minimize energy losses compared to current semiconductor materials. The findings of the research developed by the UJI Quantum Chemistry Group, in collaboration with the Technical University of Berlin and the State University of Belarus, have just been published in Nature Nanotechnology and Nano Letters journals.
Conventional semiconductor materials, essential for modern optoelectronics, emit light in all directions and, as a result, many optical devices suffer loss of energy. To achieve greater directionality "filters are currently used and light that does not run through them is lost. This circumstance, in the case of LCD monitors, involves losses of almost 50% of the light," argues Juan Ignacio Climente, scientist of the Quantum Chemistry Group. The researcher adds that "since the new nanoplatelets emit already in the desired direction, they save the filter and associated losses."
Researchers have shown that this new class of semiconductor material, made with cadmium cells, has the ability to absorb both ultraviolet and visible light from any direction and reemit it, especially perpendicular to the surface. Climente explains that this unique behaviour "is due to the 2D geometry of these nanoscopic objects and provides very interesting qualities."
Next Generation of Semiconductors
"Colloidal nanocrystals with spherical shape are a mature technology, which entered the market about three years ago in screen displays of mobile phones, tablets and the so-called quantum dot TVs," explains Climente. "Colloidal nanoplatelets are the next generation of such objects, as their rectangular shape brings about several advantages, including brighter and purer colours and now -- as we have shown -- highly directed emission." The directional emission of the nanoplatelets has its origin in mechanical and electrostatic phenomena that take place in such small structures. Each of the nanoplatelets has a surface one billion times smaller than that of an A4 sheet.
The study also shows that absorption becomes strongly directional in so-called "biphotonic processes," in which the light of a given frequency is absorbed and subsequently re-emitted with twice the frequency. This opens up additional technological possibilities in biomarkers or non-linear optics, for example," according to the researchers.
The Quantum Chemistry Group of the School of Technology and Experimental Sciences of the Universitat Jaume I is specialized in the theoretical study of nanocrystals. Their researchers model these systems with quantum mechanics tools to understand and predict their physical behaviour.