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New Perovskite Solar Cell

polarons[source]

An interdisciplinary team of researchers has laid the foundations for an entirely new type of photovoltaic cell. In this new method, infrared radiation is converted into electrical energy using a different mechanism from that found in conventional solar cells. The mechanism behind the new solid-state solar cell made of the mineral perovskite relies on so-called polaron excitations, which combine the excitation of electrons and vibrations of the crystal lattice.

[phys.org] – Scientists lay foundations for new type of solar cell
[onlinelibrary.wiley.com] – Evolution of Hot Polaron States with a Nanosecond Lifetime in a Manganite Perovskite
[cleantechnica.com] – Holy Hot Polarons, Batman! New Perovskite Solar Cell Shows Promise

Forget everything you know about solar cells and check this out. A research team based at the University of Göttingen in Germany has come up with something they call an “entirely new” way to harvest energy from sunlight. In effect, the new solar cell puts the brakes on excited electrons, extending their lifetime. The result is a more efficient solar cell, with less energy lost in the form of heat and more energy converted to electricity.

[wikipedia.org] – Polarons

A polaron is a quasiparticle used in condensed matter physics to understand the interactions between electrons and atoms in a solid material. The polaron concept was first proposed by Lev Landau in 1933 to describe an electron moving in a dielectric crystal where the atoms move from their equilibrium positions to effectively screen the charge of an electron, known as a phonon cloud. This lowers the electron mobility and increases the electron’s effective mass.

The general concept of a polaron has been extended to describe other interactions between the electrons and ions in metals that result in a bound state, or a lowering of energy compared to the non-interacting system. Major theoretical work has focused on solving Fröhlich and Holstein Hamiltonians. This is still an active field of research to find exact numerical solutions to the case of one or two electrons in a large crystal lattice, and to study the case of many interacting electrons.

Experimentally, polarons are important to the understanding of a wide variety of materials. The electron mobility in semiconductors can be greatly decreased by the formation of polarons. Organic semiconductors are also sensitive to polaronic effects, which is particularly relevant in the design of organic solar cells that effectively transport charge. The electron phonon interaction that forms Cooper pairs in low-Tc superconductors (type-I superconductors) can also be modeled as a polaron, and two opposite spin electrons may form a bipolaron sharing a phonon cloud. This has been suggested as a mechanism for Cooper pair formation in high-Tc superconductors (type-II superconductors). Polarons are also important for interpreting the optical conductivity of these types of materials.

The polaron, a fermionic quasiparticle, should not be confused with the polariton, a bosonic quasiparticle analogous to a hybridized state between a photon and an optical phonon.

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