Fig. 2From: Fabrication of 20.19% Efficient Single-Crystalline Silicon Solar Cell with Inverted Pyramid MicrostructureSEM images of nanoporous silicon (cross section in insert) with different processing time. SEM images of nanoporous silicon: a as-fabricated and b–f nanoporous silicon and cross section in inset for 1, 2, 3, 4, and 5 min processing at 35 °CBack to article page