High visible luminescence of hybrid ZnO quantum dots assembled in mesosphere for photovoltaic applications
Résumé
An innovative approach to improve the performance of thin film photovoltaic (PV) cells is based on light capture enlargement due to the introduction of energy down-shifting (DS) layer that are supposed to convert high-energy photons (UV light) into low-energy ones (visible light), which are more efficient in the PV conversion process . For this purpose, 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 scaleup process are expected for industrial photovoltaic applications. Li-doping 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 multi-step reactions are the main issues for industrial implementation. Herein, we present a quick and convenient chemical solution approach to get unique mesospheric self-assembly hybrid ZnO system with intense (PLQY = 40 - 75 %) and stable visible emissions. We also demonstrate that the use of mixture of commercial polyacrylic acid-based 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. We will then address the effects of the ZnO NPs surface functionalization - such as nature, molecular weight, concentration, ratio of the PAA-based polymers - on the enhancement of the efficiency of DS layers in solar cells technology.