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Semiconductors are materials whose electrical conductivity is between that of an insulator (like rubber) and that of a conductor (like copper). Since they were first described in the first years of the twentieth century, these materials have come to be vitally important to modern life. This is due to two of their primary applications, diodes, and transistors, which enabled the information age.
Silicon—A Commonly Used Semiconducting Material
The most commonly used semiconducting materials today are silicon (Si), in which hundreds of thousands of electrical transistors (which can occupy a state of one or zero, and give a binary unit – bit – of information) are etched to build computers, and gallium arsenide (GaAs), used in energy-efficient light-emitting diode (LED) lighting, fast electronics, optical computing and the high-efficiency photovoltaic cells that make up solar panels.
Due to the high cost of silicon production, or the scarcity of so-called rare-earth semiconductors, researchers have been seeking a new generation of semiconductor materials. Some of these are naturally occurring materials, but most are hybrids of different elements chemically transformed into new semiconductor materials.
Benefits of Halide Organic-Inorganic Perovskites
One such hybrid is halide organic-inorganic perovskite (HOIP), and its quantum physics are being exploited by researchers at the Georgia Institute of Technology to produce optoelectronic properties that are unachievable for conventional semiconductor materials.
Unlike silicon, for instance, HOIP displays an unusual level of molecular flexibility. Where silicon’s molecular structure is that of a rigid lattice, HOIP’s can withstand changes and manipulation. This means that the molecules of the material are moved along with quantum particles like electrons, enabling researchers to measure the patterns this leaves in the material and compare them with the energy put into the HOIP.
This flexibility also means that HOIP can contain numerous, diverse movements of quantum particles – governed by eccentric laws of quantum physics such as quantum superpositioning and quantum entanglement. The undulation of spinning quantum particles through HOIP in groups gives the next-generation semiconductor material a unique ability to emit light, and, more importantly, a high level of efficiency in converting light to usable electricity.
In addition to these benefits, HOIP is relatively inexpensive and simple to produce compared to common semiconductors such as silicon. Georgia Tech chemist Carlos Silva says, “HOIPs are made using lower temperatures and processed in solution. It takes much less energy to make them than current semiconductors, and you can make big batches.”
HOIP’s highly desirable optoelectronic properties are not limited to their flexibility.
Dynamic Quantum Movement
In a quantum process, negatively charged electrons excited by an energy input leaves a positively charged electron-hole in its vacated orbit. Both the electron and the electron-hole can spin around one another to form a quasiparticle known as an exciton.
The attraction between the opposing force particles binding together again in an exciton produces a lot of energy, which means they can emit light at very high levels.
Excitons can be induced in common semiconductors. However they are hard to maintain. Only in extremely cold ambient temperatures can common semiconductors keep excitons stable enough for useful capture of the energy they can produce. In HOIP, on the other hand, excitons can be stabilized at normal room temperatures.
In addition to the dynamic quantum movement of excitons, the flexible structure of HOIP allows excitons to revolve around other excitons, forming another quasiparticle called biexcitons. Yet another quasiparticle is formed in this flexible semiconductor structure when excitons spin around the nuclei of the matter’s atoms; these are called polarons.
All of this dynamic quantum movement can be exploited in next-generation semiconductor materials like HOIP much more easily – and with less cost to manufacture – than common semiconductor materials in use today.
HOIP – and other next-generation semiconductors like the flexible carbon-based polymers researched by Malika Jeffries-EL of Boston University – allows chemists and physicists to exploit quantum properties in ways that common semiconductors could never achieve.