The Nanospec project

Motivation

Silicon solar cells lose more than 20% of the energy incident from the sun because photons with an energy below the bandgap are transmitted straight through the device. Upconversion of these photons aims at increasing the efficiency of solar cells, by making also these photons useful. An upconverter generates one high-energy photon out of at least two low energy photons. These high energy photons can than be used by the solar cell.

Approach

The upconverter NaYF4:Er3+ illuminated with invisible infrared laser radiation shines bright in the visible. This is the effect of upconversion.

To achieve these goals, this project created significant progress in the science and technology of nanostructures and nanotechnology-based materials. The following detailed list of objectives were pursued:

• The theoretical modelling and simulation of the important dynamics and processes.

• Development of highly efficient, near-infrared emitting luminescent nanocrystalline quantum dots (NQD).

• Development of highly efficient upconversion phosphors.

• Development of highly energy selective, high reflection, high transmission photonic structures for photon management.

• The implementation of upconverters and nanocrystals in new matrix materials.

• The development of both crystalline and thin-film silicon solar cells that are highly efficient adapted to the use of upconverted light.

• The integration of all components into one system and testing these systems outdoors integrated into a concentrator module.

• To ensure the impact of the project in the European photovoltaic industry, a roadmap for the further exploitation was developed. Furthermore, the abundance of the involved materials was investigated and a life-cycle analysis performed.

An upconverter system with all these features was realized in the Nanospec project.

Key results