Nanotextured solar cells using aluminum as a catalyst and dopant

A black silicon solar cell fabricated using aluminum as both a catalyst and dopant is demonstrated. A nanowire/nanopyramid black silicon surface texture is grown via aluminum (Al)-catalyzed vapor-liquid-solid growth, and post-growth annealing diffuses the aluminum into the n-type substrate, forming a p-n junction. Devices with nanopyramid surface textures are found to have higher short-circuit currents and open-circuit voltages than nanowire surface textures grown at lower temperatures, and post-growth annealing times of 15-30 minutes are found to promote higher short-circuit current densities. External quantum efficiency measurements show that the highest photoconversion occurs in the red and IR regions for all devices, with low quantum efficiencies at shorter wavelengths even when the p-type silicon surface is passivated with alumina. The quantum efficiency spectra imply that the devices are limited by recombination on the illuminated side of the device. Based on these results and previous data on Al-catalyzed wires and pyramids, excess Al incorporation and Al cluster formation in the emitter are suggested as the primary factors currently limiting device performance.