Towards high-efficiency ultra-thin solar cells with nanopatterned metallic front contact

Abstract

We propose a novel design using multi-resonant absorption to achieve efficient light-trapping in ultra-thin (< 100 nm) solar cells. It is based on a patterned metallic layer which i) strongly confines light in an ultra-thin and flat absorber layer and ii) plays the role of a front contact combining high optical transparency and good electrical conductivity. This versatile approach is applied to different solar cells materials (a-Si:H, GaAs) and geometries of the patterned film (1D or 2D). We demonstrate a theoretical conversion efficiency over 20 % using a 2D silver nanogrid to enhance absorption in a 25 nm-thick GaAs absorber layer. First demonstrators were fabricated and optically characterized. This work should pave the way towards highefficiency ultra-thin solar cells.

Pushing the limits of concentrated photovoltaic solar cell tunnel junctions in novel high‐efficiency GaAs phototransducers based on a vertical epitaxial heterostructure architecture

“…Furthermore, the output voltage is significantly greater than~5 times the~1.0 V expected for typical GaAs n/p diode with a 3.5 μm thick base. The voltage increase is therefore a combination of the higher voltage expected for the higher photon fluxes [7] and also for GaAs n/p diodes having a thinner base, yielding higher Voc's [8,9].…”

“…Also, in the field of CPV, such GaAs n/p junctions have been shown to be well suited for operating at high photon fluxes [7]. Furthermore, it has been demonstrated that thin single p-n junctions can be advantageous for obtaining higher open circuit voltages (Voc) [8][9][10][11][12]. However, a thin junction may not absorb all the input photons, and the reduction in short-circuit current (Isc) typically nullifies the gain in Voc unless complicated architectures or manufacturing processes are engineered.…”