By direct numerical solution of Maxwell's equations and the semiconductor drift-diffusion equations, we demonstrate solar power conversion efficiencies in the 29%−30% range in crystalline-silicon photonic-crystal solar cells. These 3 − 12 µm thick photonic crystals, consisting of wavelength-scale inverted-pyramid arrays, absorb sunlight considerably in excess of the Lambertian limit due to wave-interference based light-trapping. It is suggested that the resulting optimized balance between bulk-Auger recombination and solar absorption occurs for a silicon thickness of 10 µm, in contrast to previous estimates of over 100 µm. Optimized n + pp + doping profiles involving low p−doping throughout most of the bulk and thin n + and p + −doping at the emitter and base regions yield ideal electronic response. For solar absorption restricted to the 300 − 1100 nm range, we obtain a short circuit current of 42.5 mA/cm 2 , an open circuit voltage of nearly 0.8 V and a fill-factor of about 87%, provided that the surface recombination velocities are below 100 cm/s. Including solar absorption in the 1100 − 1200 nm range through electronic bandgap narrowing and the Urbach optical absorption edge, our wave-interference-based light-trapping enables an additional photo-current density of 1.09 mA/cm 2 for an overall power conversion efficiency of 30%. It is shown that under solar concentration by factors of 20 and 150, the power conversion efficiencies are enhanced to 32.5% and 33.5%, respectively.

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