Crystalline silicon thin film (c-Si TF) solar cells with an active layer thickness of a few micrometers may provide a viable pathway for further sustainable development of photovoltaic technology, because of its potentials in cost reduction and high efficiency. However, the performance of such cells is largely constrained by the deteriorated light absorption of the ultrathin photoactive material. Here, we report an efficient light-trapping strategy in c-Si TFs (~20 μm in thickness) that utilizes two-dimensional (2D) arrays of inverted nanopyramid (INP) as surface texturing. Three types of INP arrays with typical periodicities of 300, 670, and 1400 nm, either on front, rear, or both surfaces of the c-Si TFs, are fabricated by scalable colloidal lithography and anisotropic wet etch technique. With the extra aid of antireflection coating, the sufficient optical absorption of 20-μm-thick c-Si with a double-sided 1400-nm INP arrays yields a photocurrent density of 39.86 mA/cm(2), which is about 76 % higher than the flat counterpart (22.63 mA/cm(2)) and is only 3 % lower than the value of Lambertian limit (41.10 mA/cm(2)). The novel surface texturing scheme with 2D INP arrays has the advantages of excellent antireflection and light-trapping capabilities, an inherent low parasitic surface area, a negligible surface damage, and a good compatibility for subsequent process steps, making it a good alternative for high-performance c-Si TF solar cells.
Keywords: Crystalline silicon thin film; Inverted nanopyramids; Light trapping; Nanosphere lithography; Solar cells.