Black silicon layer formation for application in solar cells

The structural and optical properties of black silicon by inductively coupled plasma reactive ion etching

“…Among the multitude of fabrication methods for Black Silicon, ICP-RIE seems to be the most reasonable choice for most of the named applications because of its very good repeatability and reliability, the excellent chemical and structural intactness of the produced structures, 20,48 and its applicability to all forms of silicon, irrespective of the degree of structural order. 16 However, different applications make different demands on the morphology of suitable Black Silicon nanostructures which can be hard to meet. For example, imaging devices are required to be image preserving, thus forbidding the utilization of strongly forward scattering Black Silicon structures for such applications.…”

“…15 In general, Black Silicon fabrication via reactive ion etching has proven to be astonishingly robust regarding substrate temperature variation. Besides successful structure formation at very low temperatures, 15,50 fabrication is generally possible at least up to 30 C, 16,20,51 making the technique easier applicable for high-throughput production of, e.g., solar cells. Under constant etching conditions, the main drawback of substrate temperature increase is a gradual loss of sidewall passivation, leading to a slightly shallower structure with clearly porous sidewalls and a higher correlation length of 310 nm at 20 C versus 216 nm at À38…”

“…Second, the method leaves crystallographic intact nanostructure surfaces free of chemical contaminations, in contrast, e.g., to structures obtained by VLS and wet-chemical etching or pulsed laser irradiation. Third, it cannot only be applied to poly-and monocrystalline wafers, 16 but also to amorphous or crystalline silicon thin films. 17 Lastly, the dry etching technique is capable of being integrated into in-line production facilities which is of great importance for high-throughput application fields like photovoltaics.…”

Relation between light trapping and surface topography of plasma textured crystalline silicon wafers

“…Such "black silicon" called structure leads to complete suppression of the reflection in a broad spectral range, as for example, roughly in the range of~250 to~1000 nm. The textured surfaces created by plasma etching, as for example black silicon structures, have already been reported, for example, by Schnell et al [24], by Zaidi et al [25], by Yoo et al [26,27] and recently by Otto et al [28]. Schnell et al developed a SF 6 /O 2 RIE process for the maskless texturing for the creation of black silicon [24].…”

“…Yoo et al described that by RIE texturing in a SF 6 /O 2 plasma chemistry using a parallel plate reactor powered by a 13.56 MHz RF generator, a needle-like structure is created, described as "black silicon" and corresponds to a relatively low reflection. Yoo et al achieved a higher solar cell efficiency of 15.8% based on mono c-Si material in the case of a big crater structure instead of a "black silicon" structure [26,27]. Otto et al created black silicon structures by using inductively coupled plasma RIE (ICP-RIE) in SF 6 /O 2 plasma chemistry and reaches a very effective light trapping in the range of 300-1150 nm [28].…”