Project

Discipline

semiconductors; growth; sustainability; molecular beam epitaxy; earth abundant elements

Lead
Ce projet porte sur la recherche sur des semiconducteurs faits à base d'éléments abondants sur la coute terrestre pour des applications en energies renouvelables.
Lay summary
La génération d’électricité à partir des sources renouvelables est un sujet qui a gagné et gagnera beaucoup d’importance dans les décennies à venir. Ce genre de technologie sera seulement soutenable pourvu que les matériaux employés sont composés d’éléments abondants et faciles d’extraire de la croute terrestre. Nous proposons d’explorer des matériaux semiconducteurs basés sur le phosphur de zinc dans ses deux stoichiometries : le Zn3P2 et le ZnP2. Le phosphor et le zinc sont des éléments abondants et de facile extraction. Les Zn3P2 et le ZnP2 ont des seuils d’absorption respectivement à 1.5 et 1.9eV, ce qui les rend idéales pour la fabrication de cellules solaires. Ce projet a pour but de déterminer comment synthétiser ce matériau avec des excellentes propriétés optoélectroniques et comment changer la conductivité afin de pouvoir fabriquer des cellules solaires de haut rendement et très bas cout.

Direct link to Lay Summary

Last update: 17.02.2015

Active participation

Number	Title	Start	Funding scheme

Semiconductor materials have penetrated progressively into our daily life, rendering it safer, easier and more advanced through the integration of electronic circuits in any imaginable appliances. Semiconductors also provide renewable energy harvesting solutions through the thermoelectric and photovoltaic effect. In order to render a broad deployment of these technologies globally sustainable, the abundance of the materials needs to be taken into consideration. At the same time, nanoscale materials such as nanowires have already proven to provide both extremely efficient means for energy harvesting via e.g. improved light-conversion coefficients in solar-cell prototypes and improved thermoelectric figures of merit.This proposal goes beyond the state-of-the-art semiconductor technology in that semiconducting materials made from earth-abundant elements beyond Si are explored as novel and sustainable alternatives for energy harvesting applications. I focus on the zinc-phosphide compounds Zn3P2 and ZnP2 because of their abundance and promising optical, electronic and thermo-electrical properties. Though being extremely promising for a sustainable semiconductor technology, zinc-phosphide epitaxial thin films and filamentary single crystals (nanowires) have not yet been fully mastered. Sustained by my expertise in the synthesis of ultra-high-purity compound semiconductors and nanostructures, I aim at a similar technique for the synthesis of zinc-phosphide compounds. My team will untangle the synthesis of high quality crystals and related heterostructures at the thin film and nanoscale level, and determine the doping conditions for the tailored modification of the conductivity. In summary, we will tackle the following questions: oWhat are the fundamental aspects towards achieving single-crystals with minimized structural defects, including dislocations and vacancies? oHow is it possible to obtain both defect-free Zn3P2 and ZnP2 by epitaxial growth?oHow can we adapt the growth mechanisms to create Zn3P2 and ZnP2 nanowires in a self-organized manner?oWhat is the minimal concentration of P vacancies in thin films and in nanowires?oWhat are the incorporation mechanisms of donor and acceptor impurities in Zn3P2 and ZnP2 for the modulation of conductivity? What are corresponding carrier-density limits? oAre the doping mechanisms different in thin films and in nanowires? oWhat are the essential steps towards the synthesis of high quality heterostructures based on zinc-phosphide? Is there a difference between heterostructure growth in thin films and on nanowire facets? oWhat are the optical and electrical properties of Zn3P2 and ZnP2 epitaxially grown in an ultra-pure growth chamber either as thin films or nanowires?This project will substantiate a novel materials platform for the following applications: solar cells, photo-electrochemical generation of solar fuels and harvesting of waste heat by the thermoelectric effect. It will open a new path towards solid-state renewable energy harvesting applications made with earth-abundant compounds.