Photovoltaic-thermal solar energy collectors based on optical tubes

In this work, we examine the use of oil filled tubular optical concentrators coupled with a model organic bulk heterojunction photovoltaic: poly-3-hexathiophene-[6,6]-phenyl-C61-butyric-acid methyl-ester (P3HT:PCBM) to create a photovoltaic-photothermal hybrid solar collector. The organic photovoltaic cells were fabricated onto one half of a tubular light pipe and then silicone oil was flowed inside the pipe. This allows solar energy in the visible wavelengths to be effectively converted into electricity by photocell while simultaneously; the silicone oil captures the infrared radiation (IR) part of the spectrum as heat energy. The VIS-IR power conversion efficiency for this model organic system, under normally incident AM1.5G illumination was found to be: PCE ∼ 28%, which is combined by the photovoltaic efficiency (PCE ∼ 2%) and the photothermal efficiency (PCE ∼ 26%). We further show that the oil filled tube, acts as a passive optical element that concentrates the light onto the photovoltaic and thereby increases its overall efficiency but also the range of incident angles in which the light is efficiently captured.