Thermal solar absorber made of diamond-like carbon thin films

Solar photo-thermal collectors were prepared from pure diamond-like carbon (DLC) thin films on aluminum substrates. By only changing the deposition conditions (different bias voltage) of the DC PECVD process, coatings were fabricated consisting of five sublayers with the necessary optical parameters. As expected, absorption better then 0.9 was achieved already for submicrometer absorber thickness. Accelerated thermal ageing tests performed at 200°C and 300°C in air showed that the reflectance changes only slightly. Long operating life can, therefore, be expected of such absorbers.