Black silicon solar cell: analysis optimization and evolution towards a thinner and flexible future

Abstract

Analysis and optimization of silicon nano-structured geometry (black silicon) for photovoltaic applications has been reported. It is seen that a unique class of geometry: micro-nanostructure has the potential to find a balance between the conflicting interests of reduced reflection for wide angles of incidence, reduced surface area enhancement due to the nano-structuring of the substrate and reduced material wastage due to the etching of the silicon substrate to realize the geometry itself. It is established that even optimally designed micro-nanostructures would not be useful for conventional wafer based approaches. The work presents computational studies on how such micro-nanostructures are more potent for future ultra-thin monocrystalline silicon absorbers. For such ultra-thin absorbers, the optimally designed micro-nanostructures provide additional advantages of advanced light management capabilities as it behaves as a lossy 2D photonic crystal making the physically thin absorber optically thick along with the ability to collect photo-generated carriers orthogonal to the direction of light (radial junction) for unified photon-electron harvesting. Most significantly, the work answers the key question on how thin the monocrystalline solar absorber should be so that optimum micro-nanostructure would be able to harness the incident photons ensuring proper collection so as to reach the well-known Shockley-Queisser limit of solar cells. Flexible ultra-thin monocrystalline silicon solar cells have been fabricated using nanosphere lithography and MacEtch technique along with a synergistic association of crystalline and amorphous silicon technologies to demonstrate its physical and technological flexibilities. The outcomes are relevant so that nanotechnology may be seamlessly integrated into the technology roadmap of monocrystalline silicon solar cells as the silicon thickness should be significantly reduced without compromising the efficiency within the next decade.

Studies of Black Diamond as an antibacterial surface for Gram Negative bacteria: the interplay between chemical and mechanical bactericidal activity

“…The name ‘black silicon’ originates from its deep black colour, resulting from the absorption of >99% of the visible light falling onto its surface. Black Si has now found applications in photovoltaics 5,6 and in biomedical sensing 7,8 .…”

Studies of black silicon and black diamond as materials for antibacterial surfaces

“…The name 'black silicon' originates from its deep black colour, resulting from the absorption of >99% of the visible light falling onto its surface. Originally something to be avoided, bSi has now found applications in photovoltaics [12,13] and has recently been used for biomedical sensing applications [14,15].…”

Low surface damage dry etched black silicon

“…2 Black Si nanotextured surfaces, which are textured using mask-less RIE, may be a replacement for wet-chemical texturing in silicon solar cell fabrication. [3][4][5][6][7] Black Si yields extraordinary low reflectance in an extremely broad spectral range. Thus, an additional AR coating is not required to reduce reflectance.…”

“…Black Si RIE technology also enables reduction of the Si wafer thickness to below 100 lm, 7 which avoids use of toxic materials, 13 provides easy RIE process optimization through adjustment of plasma parameters, and offers the possibility to texture any Si-based film or wafer, such as multicrystalline, 14 cast-mono, kerfless, and diamond-wire sawn Si substrates.…”