Next generation of semiconductors set to revolutionise photovoltaics and lighting
The field of semiconductors has been going through a revolution, changing the way in which technology is used in various optoelectronic devices. These are crucial components for applications in light-emitting diode displays (in televisions, computers, mobile phones) and solar cells. In a recent study, researchers have offered new insights into the emerging class of hybrid organic-inorganic semiconductors that could transform lighting and energy harvesting. Partially supported by the EU-funded QUANTUM LOOP project, scientists have examined a class of semiconductors called halide organic-inorganic perovskite (HOIP). Their findings were published in the journal ‘Nature Materials’. According to a news release by the Georgia Institute of Technology, HOIPs are energy efficient and “easy to produce and apply.” In the same news release, Prof. Carlos Silva from Georgia Tech’s School of Chemistry and Biochemistry highlights the advantages of HOIPs, saying that they “are made using low temperatures and processed in solution.” He adds: “It takes much less energy to make them, and you can make big batches.” The news release further explains: “It takes high temperatures to make most semiconductors in small quantities, and they are rigid to apply to surfaces, but HOIPs could be painted on to make LEDs, lasers or even window glass that could glow in any color from aquamarine to fuchsia. Lighting with HOIPs may require very little energy, and solar panel makers could boost photovoltaics’ efficiency and slash production costs.” The news item refers to HOIP as “a sandwich of two inorganic crystal lattice layers with some organic material in between them.” Light emission processes Semiconductors in optoelectronic devices convert electrical energy into light and light into energy. The researchers have focused on the processes involved with light generation. “The trick to getting a material to emit light is, broadly speaking, to apply energy to electrons in the material, so that they take a quantum leap up from their orbits around atoms then emit that energy as light when they hop back down to the orbits they had vacated.” It states: “Established semiconductors can trap electrons in areas of the material that strictly limit the electrons’ range of motion then apply energy to those areas to make electrons do quantum leaps in unison to emit useful light when they hop back down in unison.” In the case of new hybrid semiconductors “excitonic properties are very stable at room temperature,” unlike traditional semiconductors where these properties “are only stable at extremely cold temperatures,” according to Prof. Silva. The news release explains: “An electron has a negative charge, and an orbit it vacates after having been excited by energy is a positive charge called an electron hole. The electron and the hole can gyrate around each other forming a kind of imaginary particle, or quasiparticle, called an exciton.” Prof. Silva emphasises that the binding energy, or the positive-negative attraction in an exciton, is “a very high-energy phenomenon, which makes it great for light emitting.” The news release also summarises the dynamics that lead to the formation of other quasiparticles, biexcitons and polarons. The QUANTUM LOOP (Quantum Light Spectroscopy of Polariton Lasers) project was set up to “develop the essential photo-physical knowledge-base through novel optical spectroscopies,” as stated on CORDIS. The project has “a long term perspective of creating industrially viable polariton lasers embodying perovskites.” For more information, please see: QUANTUM LOOP project
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