Reciprocal space engineering for photon management in ultrathin solar cells

Using the reciprocal space, two types of structures are simple to identify: simple periodic (photonic crystals), which have high diffractive efficiencies but sparse resonances (narrow-band), and random structures, with a continuous reciprocal space (broadband) but suffering from low diffraction efficiencies. A third type, quasirandom structures, lies in between; these provide high diffractive efficiency over a target wavelength range, which is broader than simple photonic crystals but narrower than a random structure. These structures are promising for ultrathin solar cells due to their broader nature. We present our numerical work towards evolving simple photonic crystals in quasirandom structures, and our fabrication approach based on polymer-blend lithography, with initial results on solar cells.