Highly absorbing and high lifetime tapered silicon microwire arrays as an alternative for thin film crystalline silicon solar cells

Abstract

We report cryogenic inductively coupled plasma reactive ion etching (ICPRIE) etched tapered silicon microwires are ideal light trapping structures with extremely low (1.08% between 400 nm-1100 nm under normal incidence) reflectivity. We show that these tapered microwire arrays absorb 90.12% of incident light under normal incidence in an effectively 20 μm thick silicon when embedded in a polymer and peeled off the substrate, making them an attractive alternative for achieving high efficiency in thin film crystalline silicon solar cells. We show that microwave photoconductivity decay measurements as a simple quick way to measure carrier lifetimes in etched microwires under various liquid surface passivation techniques to estimate surface recombination velocities. The etched structures demonstrate >1 μs lifetimes.