Thin film luminescent solar concentrators : new polymer matrices and organic fluorophores for improved device performance

Thin-film luminescent solar concentrator (LSC) devices were investigated in this thesis. In the first part of this work, alternative matrices based on fluoro-polymers were proposed with the aim of fabricating efficient and environmentally stable LSC devices to substitute state-of-the-art PMMA-based LSC devices. The first matrices examined are based on three different fluoro-polymers based on poly(vinylidenefluoride) each blended with PMMA. The second alternative system studied is a mono-component photo-crosslinkable polyurethane-based fluorophore matrix. An optimization of the photovoltaic (PV) performance of all these new fluorinated LSC devices was carried out by studying the effect of organic dye (Lumogen F Red 305) concentration and matrix thickness on the PV behaviour of the LSC. The effect of varying PMMA content in the fluorinated blends on the PV performances was also investigated, as well as the adhesion strength onto glass substrates. All the optimized LSCs were subjected to weathering tests for 1000 hours of continuous light exposure to highlight the effect of the host matrix system on LSC degradation. It was found that new fluorinated systems outperformed standard PMMA-based LSC devices in terms of long-term lifetime. Being their efficiency comparable to PMMA-based LSC’s, the new systems proposed may be employed as alternative host matrices to fabricate LSC devices with long-term durability and high PV efficiency. In the second part of this thesis, efficient thin-film LSCs were fabricated using tetracene-doped anthracene cocrystals as novel fluorescent systems dispersed in a PMMA matrix. The variation of the solvent system, of the processing temperature and PMMA:Ac:Tc weight ratio led to the observation of different cocrystal morphologies that influenced the performance of the corresponding LSC devices. The use of molecular cocrystals as novel fluorescent species in LSC devices opens up new strategies for the preparation of efficient fluorophores for LSC applications. In addition, due to the higher photostability of molecular crystals compared to common organic dyes, LSC device lifetime is also expected to benefit from their use.