I will discuss two applications of luminescent nanoparticles: perovskite nanoparticles for phosphors and light-emitting diodes (LEDs), and lead sulfide semiconductor nanoparticles for luminescent downconverters in photovoltaics.
Cesium lead halide perovskite nanoparticles can give efficient emission in LEDs, but mixing these nanoparticles to give white light emission is problematic due to rapid halide exchange between nanoparticles of different compositions. I will show how mixtures of certain nanoparticle compositions can be stabilised, and will discuss the physics of energy transfer in the mixed films. I will also present measurements of defect-state emission in 2-d perovskite structures.
The efficiency of photovoltaic devices could be improved beyond the Shockley-Queisser limit if it were possible to convert higher-energy photons in the solar spectrum into two bandgap-energy photons. The process of singlet exciton fission in organic semiconductors is a promising route to achieve this, but the challenge is to achieve photon emission from both of the triplet excitons generated. Triplet energy transfer into emissive lead sulfide nanoparticles has been demonstrated, with the potential to achieve a “photon multiplier film” than could be applied to the front surface of a silicon solar cell. I will present recent progress in this area, aiming to achieve highly luminescent nanoparticles whilst still allowing triplet excitons to tunnel easily onto the particles from a surrounding singlet fission material.