Back Mirror-Free Selective Light Absorbers for Thermoelectric Applications

Improving light absorption is essential for the development of solar thermoelectric generators. Most efficient light absorbers require a back mirror (a thick metal film) to reduce the reflectivity by promoting the interference between the incident and the reflected light. However, the presence of thick a continuous metal film supposes a limitation for thermoelectric applications, as it behaves like a shortcut of the Seebeck voltage. In this work, a back mirror-free selective light absorber is presented, designed for the fabrication of thermoelectric devices. The combination of a high and a low refractive index material covered by a semi-transparent electrode is optimized. As a difference to the back mirror, the semi-transparent electrode can be patterned to prevent the quenching of the Seebeck voltage. Thanks to this, the low refractive index material can be replaced by a transparent thermoelectric, enabling efficient heat-to-energy conversion with negligible loss of absorption performance.