SPLTRAK Abstract Submission
Multiresonant Light Trapping in Ultra-thin Solar Cells with Transparent Quasi-random Structures
Eduardo Camarillo Abad, Hannah J. Joyce, Louise C. Hirst
University of Cambridge, Cambridge, United Kingdom

Ultra-thin solar cells offer advantages across different material systems such as cost reductions, flexible form factors and tolerance to absorber defects, but suffer from low absorption of incident photons. Advanced light management techniques beyond antireflection coatings and rear mirrors are needed to extend the optical path length in the absorber layer. Coupling incident illumination to waveguide modes by integrating a scattering structure can localise the field within the absorber layer and increase device performance. However, the thinnest device stacks have reduced modal structures and so introducing multiple waveguide resonances across the spectrum for maximal absorption enhancement is challenging in ultra-thin length-scales. We propose transparent (i.e. dielectric/high band gap semiconductor) quasi-random scattering structures as multiresonant light-trapping textures for ultra-thin devices, offering key advantages: i) richer device modal structure as a consequence of unhindered field propagation within the light trapping layer, effectively making the solar cell a thicker waveguide than with a metallic texture, and ii) richer scattering profile compared to ordered photonic crystals that can fully exploit the available modal structure, yield broadband absorption enhancement and be more tolerant to design variability. By performing an in-depth study of the available parameter space for QR structures, we provide design guidelines for optimal performance that can maximise these advantages across different material systems.