Hyperspectral guided-mode quantum efficiency: A novel characterization technique for thin-film photovoltaics

We present a novel and comprehensive technique to measure the internal quantum efficiency of light absorbed as a guided-mode in a thin-film photovoltaic (TPV) over a broad range of wavelengths. Evanescent prism coupling is utilized to selectively excite individual guided-modes at a given wavelength and polarization across a broad spectrum. The Guided-Mode Quantum Efficiency (GIQE) provides a direct quantitative method to design TPVs which can optimize light trapping through guided-modes for higher power conversion efficiency. Furthermore, using theoretical photocarrier generation profile and GIQE of a specific guided-mode, we can probe the spatially dependent charge extraction in the active layer in a direction normal to the substrate. Therefore this technique enables the identification of regions of poor performance due to recombination and trapping within the active layer in a TPV device.