Plasmonic effects in amorphous silicon thin film solar cells with randomly textured metal back contact were investigated experimentally and numerically. The influence of different metal back contacts with and without ZnO interlayer was studied and losses in the individual layers of the solar cell were quantified. The amorphous silicon thin film solar cells were prepared on randomly textured substrates using large area production equipment and exhibit conversion efficiencies approaching 10%. The optical wave propagation within the solar cells was studied by Finite Difference Time Domain simulations. The quantum efficiency of solar cells with and without ZnO interlayer was simulated and the interplay between the reflection, quantum efficiency and absorption in the back contact will be discussed.

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The influence of nanotextured metallic back contacts on light trapping and plasmonic losses of amorphous silicon solar cells was investigated. The optical losses of the back contact are determined by the texture of the metallic back contact and the dielectric constant of the interlayer between the solar cell and the metal back contact. The investigations show that the optical losses are highest if nano features are present at the back contact, while the texture of the front contact which propagates through the layer stack exhibits only a minor effect on the optical losses. V C 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4793415]Light trapping or photon management in thin film solar cells allows for both a reduction of the reflection losses and a gain in the optical path length of the incident light inside the absorber layer. 1,2 Light trapping can be maximized if the front and the back contacts are textured. The rough back contact scatters and diffracts longer wavelengths light, 3,4 but also enhances the optical absorption within the metaldielectric interface. [5][6][7][8][9] Plasmonic absorption in the back contact can be reduced by introducing a textured dielectric layer with a refractive index lower than that of amorphous silicon. Aluminum doped zinc oxide (ZnO) is very often used as an interlayer between the metal back contact and the silicon p-i-n diode. 10,11 Surface textures with lateral dimensions approaching the effective wavelength of the incident light in the dielectric interlayer can couple incoming light to plasmon modes. 13 Schematic sketches of thin film solar cells with and without ZnO interlayer are shown in Figs. 1(e)-1(h). For interlayers prepared by sputtering, the surface texture is determined by the roughness and the morphology of the nlayer of the p-i-n diode. Thin (100 nm) and thick (400 nm) interlayers exhibit almost identical roughness. The back contact roughness can be controlled by wet chemical etching of the zinc oxide interlayer in hydrochloric acid. The influence of ZnO interlayer surface morphology on the quantum efficiency and the short circuit current of the solar cell was investigated in this study.The amorphous p-i-n solar cells were prepared by plasma enhanced chemical vapor deposition (PECVD) on 1.43 m 2 glass substrates. Due to the high defect density and low carrier diffusion lengths of amorphous silicon, 12 the solar cell is very thin with total thickness of 320 nm. The glass substrates were coated with a randomly textured tin oxide (SnO 2 ) layer. Further details on the optical and electrical properties of the amorphous silicon layers are given in Ref. 12. The zinc oxide interlayers and silver (Ag) back) back contacts were prepared by DC magnetron sputtering. The zinc oxide interlayers exhibit a thickness of 400 nm. Cross sections of solar cells with and without zinc oxide interlayer are shown in Figs. 1(e)-1(h). The ZnO interlayer was then subjected to wet chemical etching in a 3% hydrochloric acid (HCl) solution for various etching times. The etchin...

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A dry plasma etching process for phosphorus silicate glass (PSG) in a SiN‐PECVD batch reactor is developed. In the same reactor PSG etching and anti‐reflective coating (ARC) can be performed successively. To demonstrate industrial feasibility, screen‐printed solar cells are manufactured and compared with cells prepared by a standard wet chemical process. Copyright © 2003 John Wiley & Sons, Ltd.

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