Chemically Unique Hybrid Substance Could Redefine Semiconductor Effectiveness
Lane Long posted on March 26, 2018 |
Georgia Tech graduate research assistant Felix Thouin in a lab where laser light is used to measure materials qualities. (Image courtesy of Allison Cater, Georgia Tech.)
Georgia Tech graduate research assistant Felix Thouin in a lab where laser light is used to measure materials qualities. (Image courtesy of Allison Cater, Georgia Tech.)

A study spearheaded by scientists at Georgia Tech has found that an obscure class of crystal could improve the way we light and power our world. The subatomic behavior of these crystals is fluid, dynamic and, frankly, bewildering in the context of some established laws of quantum physics. However, this latest study, completed early this month, shows that weirdness doesn’t necessarily mean ineffectiveness. In fact, the substance could be the key to more efficient electric lighting—perhaps even across a full rainbow of colors.

HOIPs

Hybrid organic-inorganic perovskites, or HOIPs, are not a recently discovered phenomenon. While they have been known to science for many years, their remarkable potential for use as semiconductors has only begun to be explored. HOIPs are cheap to produce en masse, require low energy inputs to make, and are highly efficient in both absorbing and emitting all wavelengths of light. Until now, however, most physicists believed that HOIPS were unsuitable as semiconducting materials. The molecular foundation of HOIPs is three dimensional, whereas traditional semiconducting options like silicone and graphene are rigidly flat. In addition, the atomic lattice of the crystals is in constant motion at room temperature, resulting in a molecular scene that more closely resembles tiny boats tossed about by a raging ocean than the still and stable sheet-like appearance of conventional materials. 

A Particle Party

The other feature that makes HOIPs unique at the nanoscale involves the behavior of their electrons. In all semiconductors, electrons are free to “escape” from their normal orbit to pursue other positively charged energy levels. This leaves a positively charged void in the form of the usual orbit—which, of course, is constantly attracted to the negatively charged electron roaming freely at other energy levels. The result is a kind of subatomic dance, wherein the orbital voids and the electrons move around each other constantly. The collective term for this formation is an “exciton.”

What separates HOIPs from silicon and graphene is the fact that their excitons themselves pair off, forming biexcitons at an abnormally high rate. Biexcitons have extremely desirable energetic properties, including the ability to both absorb and emit very high percentages of the total light to which they’re exposed. Further, altering the exact chemical makeup of the HOIP will adjust the width of the biexcition states, thus making it possible to give off any desired wavelength of light.

Powering the Future?

In the long term, a total switch to these hybrid semiconductors could come with a long list of advantages. First, the same amount of energy can be used to manufacture far more HOIP semiconductors than silicone- or graphene-based iterations. In addition to the obvious environmental benefits, this manufacturing process also makes these semiconductors cheap. They are also extremely effective in transmitting light, which means that their use could reduce the total power needed to light up existing fixtures. Further, they have the potential to be the most efficient power-converting material ever used in solar panels. Even with relatively little optimization, HOIPs have shown the ability to cross a remarkably high threshold in photovoltaic conversion efficiency. And, of course, it doesn’t hurt that they’re capable of throwing off light in pretty colors, either.

For more interesting semiconductor research, check out how Graphene Could Reduce the Cost of Semiconductor Wafers.

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