Periodically textured glass for 20% bottom cell current increase in a-Si:H/μc-Si:H tandem solar cells

Enhancing light absorption in a thin film silicon tandem solar cell fabricated on a reactive ion etched nano-structured glass surface

“…Earlier reported results show an improvement of ~1.0% in PCE of a-Si/mc-Si tandem solar cells when a hemi-spherical texture was used and where the sizes of the textures were within a range of 500 nm to 2500 nm [14]. A 1000 nm periodic 2D grating structure of front TCO leads to an improvement in device efficiency of 3.1 percentage points, from 6.9% to 10.0% [15]. Here, the EQE spectra in the longer wavelength region shows a significant improvement but in the shorter wavelength region EQE was reduced, probably because of increased optical absorption in the 2D gratings structure, as reported in [15].…”

“…A 1000 nm periodic 2D grating structure of front TCO leads to an improvement in device efficiency of 3.1 percentage points, from 6.9% to 10.0% [15]. Here, the EQE spectra in the longer wavelength region shows a significant improvement but in the shorter wavelength region EQE was reduced, probably because of increased optical absorption in the 2D gratings structure, as reported in [15]. An inverted nano-pyramid structure, obtained by texturing a c-Si wafer and then depositing a a-Si top cell, resulted in an improvement in J sc from 9.6 to 13.4 mA cm −2 and in PCE from 10.3% to 13.3% [16].…”

“…This is popularly achieved with the help of a textured surface [2][3][4][5][6][7], among which a nano-cone type surface texture [7,8] or a combination of surface texture and anti-reflection layer [9] are helpful. The textured front surface was demonstrated in a single junction type [2-5, 8, 10, 11], as well as tandem solar cells [12][13][14][15][16][17], but details of the mechanisms of improvement are limited. In addition to the nanocone, an inverted pyramid structure [18][19][20] is also one of the most popular shapes of surface texture.…”

“…It was reported that submicron surface texturing shows an improvement in efficiency of a-Si/mc-Si tandem solar cells by about 1% [14]. Two dimensionally periodic transparent conducting layers show an improvement in device efficiency from 6.9% to 10.0% [15]. An amorphous silicon/c-Si tandem cell with nano-pyramidal texturing of the front surface shows an improvement in power conversion efficiency (PCE) from 10.3% to 13.3% [16].…”

Gen5 production tool for light management textures

“…The top left figure shows the result of using optimized TCO growth conditions in order to obtain a native roughness (Fluor doped Tin Oxide -FTO), top right is a typical example of a texture that results from a post treatment like wet chemical etching (HCl etched Aluminium doped Zinc Oxide -AZO) and the bottom pictures display results of the OM&T approach of using a nano-imprinted 1D (left) or 2D (right) periodic textured superstrate before TCO deposition (sputtered AZO). Earlier investigations [2]- [3] demonstrated that using such optimized periodic textures can result in a 10-20% current gain relative to a reference commercial FTO glass for thin film silicon tandem solar cells. Figure 2 shows the comparison of EQE spectra of identical a-Si:H/µc-Si:H tandem solar cells deposited on an optimized 2D grating texture, on a commercial FTO superstrate and on a flat reference.…”