The role of oxide interlayers in back reflector configurations for amorphous silicon solar cells

Abstract

Thin oxide interlayers are commonly added to the back reflector of thin-film silicon solar cells to increase their current. To gain more insight in the enhancement mechanism, we tested different back reflector designs consisting of aluminium-doped zinc oxide (ZnO:Al) and/or hydrogenated silicon oxide (SiO x :H) interlayers with different metals (silver, aluminium, and chromium) in standard p-i-n a-Si:H solar cells. We use a unique inverse modeling approach to show that in most back reflectors the internal metal reflectance is lower than expected theoretically. However, the metal reflectance is increased by the addition of an oxide interlayer. Our experiments demonstrate that SiO x :H forms an interesting alternative interlayer because unlike the more commonly used ZnO:Al it can be deposited by plasma-enhanced chemical vapour deposition and it does not reduce the fill factor. The largest efficiency enhancement is obtained with a double interlayer of SiO x :H and ZnO:Al.

On the potential of light trapping in multiscale textured thin film solar cells

“…The p-layer, i-layer and n-layer of the p-i-n diode exhibit a nominal thickness of 20 nm, 300 nm and 10 nm, respectively. Afterwards, a 100 nm ZnO layer is prepared on the p-i-n diode to reduce parasitic losses in the metal back reflector [3,[6][7][8]22,23]. Finally, a silver (Ag) back reflector is deposited.…”

“…Wide band gap silicon oxide (Si 1-x O x ) layer is used as p-layer to minimize the optical losses of the front contact [7,8,21]. The p-layer, i-layer and n-layer of the p-i-n diode exhibit a nominal thickness of 20 nm, 300 nm and 10 nm, respectively.…”

“…High energy conversion efficiencies and short circuit currents can be achieved by efficient light trapping (photon management). Commonly, the absorption of light is enhanced by texturing the front contact (solar cells in superstrate configuration) or back contact (solar cells in substrate configuration) [1][2][3][4][5][6][7][8][9][10][11]. The textured front contact of the solar cells has the function to improve the incoupling and scattering of the incident light.…”

Improving the Back Surface Field on an Amorphous Silicon Carbide Thin‐Film Photocathode for Solar Water Splitting

“…Second, to look at the effects of the catalyst and electrolyte,t he electrochemical characteristics were measured (Figure 7c). [30,32] Figure 7b showst hat when no (n)nc-SiO x :H is included, ab ig fraction of the light with wavelengths higher than 450 nm is not absorbed. The (n)nc-SiO x :H thickness can change the optical performance of the photoelectrode, as well as affect possible tunnelling effects through this layer.M oreover,i ft he layer is too thin, pinholes might appear creating short-circuit paths.…”

Back-contacted BaSi_2 solar cells: an optical study

“…At the back side, fingers of p-and n-doped SiO x are alternated and contacted with silver, to create hole-and electron-selective contacts, respectively. Such doped materials are chosen for their relatively large bandgap (E g ~2 eV), ensuring transparency at long wavelengths [30,31], and for their good thermal stability. The gaps between metallic stripes is covered with a distributed Bragg reflector (DBR), significantly reducing transmittance losses which would otherwise take place.…”