Non-reciprocal meta-surfaces for nanophtonic light trapping: Optical isolators versus solar cells

Nano-photonic concept has been shown to be very effective for boosting solar cell conversion efficiency. In this work, the novel concepts of non-reciprocality and chiral meta-surface are demonstrated to be very useful for photovoltaics. The asymmetric chiral patterns are designed and optimized using genetic algorithm. The enhanced optical absorption is observed and it is attributed to the non-reciprocal nature of the solar cell front meta-surface. The asymmetric solar cell front surface enhances the anti-reflection and, at the same time, forbids the photon escape once it enters the devices. This concept is very similar to optical isolators where one-way transmission is intentionally designed for enhanced optical diode effect. Preliminary experimental results are supplied to confirm the superiority of asymmetric chiral design. The ongoing experimental effort is adjusting the PECVD deposition conditions to boost the efficiency on patterned substrates.