Nanowires for energy: A review

Abstract

Semiconductor nanowires (NWs) represent a new class of materials and a shift from conventional two-dimensional bulk thin films to three-dimensional devices. Unlike thin film technology, lattice mismatch strain in NWs can be relaxed elastically at the NW free surface without dislocations. This capability can be used to grow unique heterostructures and to grow III-V NWs directly on inexpensive substrates, such as Si, rather than lattice-matched but more expensive III-V substrates. This capability, along with other unique properties (quantum confinement and light trapping), makes NWs of great interest for next generation optoelectronic devices with improved performance, new functionalities, and reduced cost. One of the many applications of NWs includes energy conversion. This review will outline applications of NWs in photovoltaics, thermoelectrics, and betavoltaics (direct conversion of solar, thermal, and nuclear energy, respectively, into electrical energy) with an emphasis on III-V materials. By transitioning away from bulk semiconductor thin films or wafers, high efficiency photovoltaic cells comprised of III-V NWs grown on Si would improve performance and take advantage of cheaper materials, larger wafer sizes, and improved economies of scale associated with the mature Si industry. The thermoelectric effect enables a conversion of heat into electrical power via the Seebeck effect. NWs present an opportunity to increase the figure of merit (ZT) of thermoelectric devices by decreasing the thermal conductivity (κ) due to surface phonon backscattering from the NW surface boundaries. Quantum confinement in sufficiently thin NWs can also increase the Seebeck coefficient by modification of the electronic density of states. Prospects for III-V NWs in thermoelectric devices, including solar thermoelectric generators, are discussed. Finally, betavoltaics refers to the direct generation of electrical power in a semiconductor from a radioactive source. This betavoltaic process is similar to photovoltaics in which photon energy is converted to electrical energy. In betavoltaics, however, energetic electrons (beta particles) are used instead of photons to create electron-hole pairs in the semiconductor by impact ionization. NWs offer the opportunity for improved beta capture efficiency by almost completely surrounding the radioisotope with semiconductor material. Improving the efficiency is important in betavoltaic design because of the high cost of materials and manufacturing, regulatory restrictions on the amount of radioactive material used, and the enabling of new applications with higher power requirements.

Photodetecting properties of single CuO–ZnO core–shell nanowires with p–n radial heterojunction

“…These lead to an increase of the light confinement and photosensitivity 6 , features essential for applications such as photodetectors 7 , lasers 8 , solar cells 9 , photocatalysis 10 , etc. Additionally, the progress made in tuning the material properties during their synthesis led to the development of heterostructure nanowires with different architectures, such as axial, radial or branched 11 – 13 . Amidst them, radial core–shell heterostructure nanowires obtained using two semiconductors arranged in a type II (staggered gap) band alignment augmenting the charge carrier separation efficiency.…”

A methodological review on material growth and synthesis of solar-driven water splitting photoelectrochemical cells

“…Unlike thin-lms, the strain relaxation of nanostructures hinders defect formation because of their low dimensionality. 29 A large surface-to-volume ratio is also another advantage of nanostructures when it comes to PEC cells due to the increased surface area which can enhance light absorption and surface reactions. Faqrul A. Chowdhury et al recently reported on a PEC cell with vertically aligned InGaN nanosheets grown by MBE ( Fig.…”

Nanoarchitectonics for Wide Bandgap Semiconductor Nanowires: Toward the Next Generation of Nanoelectromechanical Systems for Environmental Monitoring

“…A considerable number of review papers are available on the incredibly rapid progress of such semiconductor nanowires and their diverse applications. [54][55][56][57] However, very few of them have considered the current status of WBG nanowires-based sensing devices with an emphasis placed on environmental monitoring applications. On the basis of these observations, this article provides a comprehensive review of the research activities focusing on the use of WBG semicon-ductor nanowires of SiC, group III-nitrides, and diamond for environmental monitoring applications.…”