Applications of polymer nanocomposites as encapsulants for solar cells and LEDs: Impact of photodegradation on barrier and optical properties

Abstract

The search for higher efficiency organic materials and device architectures has been of greatest interest in the organic photovoltaic community, but the issue concerning the stability of devices has received little attention. The next generation of lighting industry, phosphor-converted white light-emitting diodes (LEDs) is becoming a mature technology which needs extended lifetime. As promising as the performances of a material are, long-term stability is just as important as initial efficiency. Organic Solar Cells (OSC) have to be encapsulated to overcome the problem of their sensitivity to oxygen and moisture. High quality encapsulation layers are then critical for improving the life span of OSC. To meet the encapsulation requirements, different approaches have been adopted such as single layer and multilayer encapsulation. A variety of materials have been developed to face the barrier issue, but the challenge is still to develop high gas barrier materials with required photostability.Recent research focused on nanocomposites is based on various kinds of nanofillers, such as phosphors or zeolites. Phosphor particles display an emission in the visible domain upon a UV excitation, and the luminescent polymer/phosphor nanocomposites can be used for eco-energetic lighting devices such as LEDs or as multifunctional coatings for Organic Solar Cells. Zeolites as nanofillers are expected to improve water barrier properties, which makes polymer/zeolite nanocomposites good candidates for encapsulation of organic solar cells. The photostability of the materials and the durability of the barrier properties are then challenging for developing new applications in this domain.