Efficient Light Trapping in Inverted Nanopyramid Thin Crystalline Silicon Membranes for Solar Cell Applications

Abstract

Thin-film crystalline silicon (c-Si) solar cells with light-trapping structures can enhance light absorption within the semiconductor absorber layer and reduce material usage. Here we demonstrate that an inverted nanopyramid light-trapping scheme for c-Si thin films, fabricated at wafer scale via a low-cost wet etching process, significantly enhances absorption within the c-Si layer. A broadband enhancement in absorptance that approaches the Yablonovitch limit (Yablonovitch, E. J. Opt. Soc. Am.1987, 72, 899-907 ) is achieved with minimal angle dependence. We also show that c-Si films less than 10 μm in thickness can achieve absorptance values comparable to that of planar c-Si wafers thicker than 300 μm, amounting to an over 30-fold reduction in material usage. Furthermore the surface area increases by a factor of only 1.7, which limits surface recombination losses in comparison with other nanostructured light-trapping schemes. These structures will not only significantly curtail both the material and processing cost of solar cells but also allow the high efficiency required to enable viable c-Si thin-film solar cells in the future.

Realization of Quasi‐Omnidirectional Solar Cells with Superior Electrical Performance by All‐Solution‐Processed Si Nanopyramids

“…In fact, besides utilizing outstanding passivation layers, developing Si nanostructures with low surface enhancement is also an effective approach to reduce carrier recombination 21. On this aspect, Si nanopyramids (SiNPs) have extremely attracted interests due to the fact that they have low surface enhancement, while excellent antireflection and light trapping effect are retained 24, 25, 26, 27. Therefore, SiNPs have been successfully demonstrated to bring benefits for solar cells, especially in ultrathin c‐Si solar cells 28, 29, 30.…”

All-back-contact ultra-thin silicon nanocone solar cells with 13.7% power conversion efficiency

“…Reducing a Si absorber thickness from 200 to sub-10 mm can potentially have a large impact on reducing the module cost further and enabling light-weight installation. The conventional surface texturing with alkaline or acidic solution for sub-10-mmthick Si substrates requires additional masking steps including photolithography 15 , and it is hard to implement on thin substrates with high yield 16 . In the past several years, significant effort has been focused on enhancing the light absorption by nanoscale light trapping using nanowires 8,[17][18][19] , nanocones [20][21][22] , nanodomes 7 and nanoholes [23][24][25][26] .…”

Mie resonance-mediated antireflection effects of Si nanocone arrays fabricated on 8-in. wafers using a nanoimprint technique

“…In contrast, the reflectance of the NC array was less than 10% over a broad wavelength range. Such an antireflection effect is notable, even without a dielectric layer coating [3][4][5].…”

“…The advantages of Si as an active material for a PV device include abundance on earth, competitive fabrication cost, and superior device performance. Further efforts to lower the cost to generate electricity have led to light-trapping strategies that improve optical absorption in Si [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. For example, nanostructures exhibit remarkable absorption enhancement, and a graded refractive index and scattering enable desirable antireflection effects [2][3][4][5][6][7][8][9][10][11][12][13].…”