Sol-gel processing of hybrid ZnO quantum dots mesospheres for LED applications
Résumé
An important economic improvement of white light emitting diode is based on the use of lanthanidefree
phosphors that are supposed to convert UV light into visible one, thanks to downconversion (DS) process.
ZnO nanoparticles (NPs) have aroused an increasing interest since they possess a variety of intrinsic defects
that provide light emission in the visible range without the introduction of any additional impurity . However ,
high photoluminescent quantum yield (PLQY), green/yellow emission, stable dispersion and easy scale–up
process are expected for industrial applications. Lidoping and polymer surface modifications of ZnO
nanoparticles are mainly used in order to reach high PLQY (>30%) but PLQY decay over few days, uses of
sophisticated polymers or multistep reactions are the main issues for industrial implementation.
Recently , we developed and patented an industrycapable (in terms of legislation concerns) and cost effective
chemical solution process to get unique mesospheric selfassembly hybrid ZnO system with intense (PLQY
= 4075%) and stable visible emission. This hierarchical structure revealed to be efficient
scatterer , resulting in a significant increase of the lightharvesting capability . W e also demonstrate that the
use of mixture of commercial polyacrylic acidbased polymers can provide scalable amounts of ZnO NPs
clear water suspensions that can be dried and dispersed again in water without compromising the functional
performance (e.g. transparency and PLQY) of the final DS layer.
Herein, we will address the effects of the ZnO NPs surface functionalization such as nature, molecular
weight, concentration, ratio of the P AAbased polymers and selfassembly process but also the impacts of
transition metal dopings (nature and content) on the enhancement of the efficiency and on the control of the
emission colour light of DS thin films in LED technology . Some examples of LED prototypes will also be
presented.