Improved Metal Oxide Electrode for CIGS Solar Cells: The Application of an AgOX Wetting Layer

Abstract

Oxide/metal/oxide (OMO) layer stacks are used to replace transparent conductive oxides as front contact of thin-film solar cells. These multilayer structures not only reduce the overall thickness of the contact, but can be used for colouring of the cells utilizing interference effects. However, sheet resistance and parasitic absorption, both of which depend heavily on the metal layer, should be further reduced to reach higher efficiencies in the solar cells. In this publication, AgOX wetting layers were applied to OMO electrodes to improve the performance of Cu(In,Ga)Se2 (CIGS) thin-film solar cells. We show that an AgOX wetting layer is an effective measure to increase transmission and conductivity of the multilayer electrode. With the presented approach, we were able to improve the short-circuit current density by 18% from 28.8 to 33.9 mA/cm2 with a metal (Ag) film thickness as low as 6 nm. Our results highlight that OMO electrodes can be an effective replacement for conventional transparent conductive oxides like aluminium-doped zinc oxide on thin-film solar cells.

Flexible design of building integrated thin‐film photovoltaics

“…This improvement was possible due to two effects: First, the application of the AgO X wetting layer was successfully integrated in the OMO electrode also on module level, resulting in both lower sheet resistance and higher transmission of the electrode. 11 Second, in contrast to the previously studied cells, the modules presented here were n AZO $ 2.0, n foil $ 1.7, n glass $ 1.6 and n air $ 1.0, the encapsulation reduces the reflection similar to an antireflection layer. 13 Consequently, more light is transmitted into the cell and a higher current is generated.…”

“…An AgO X wetting layer was used to increase homogeneity and conductivity of the Ag layer. 11 Prior to deposition of the electrodes, the sputter rates of the AZO deposition processes were determined by thickness measurements single-layer reference samples on glass substrates with a relative error of 2%. To determine the deposition rate of silver, samples with a sandwich of two AZO layers with and without a silver layer inbetween were prepared.…”

“…The application of oxide/metal/oxide electrodes instead of the typical front contact TCO layer offers the opportunity to tune the reflected spectrum of the solar cell while maintaining comparable high conductivity and transparency of the electrode. 11,13,19,20 The maxima of the reflection spectrum can be shifted by changing the thickness of the oxide layers to produce a wide range of colours. Here, we report on the fabrication of coloured OMO/CIGS solar modules.…”

“…13 In separate study, we reported on processes for improved OMO electrodes by the application of a wetting layer. 11 For the present publication, these improved processes including the $1 nm thick AgO x wetting layer were translated from sample size 10 Â 10 cm 2 to size 30 Â 30 cm 2 in an in-line sputter tool, as described in the methods section, to prepare coloured samples. Additionally, standard processes for the monolithic interconnection of cells were applied to verify the compatibility of OMOelectrodes with the current industry standard processes.…”

Tunable Photovoltaics: Adapting Solar Cell Technologies to Versatile Applications

“…An improved electrode with the implementation of a wetting layer enabled a PCE of about 13%. [339] Stimulated by the pioneering work of Kats, Capasso and co-workers on strong interference effects in highly lossy media, [80,340] many relevant demonstrations of decorative PV based on optical absorbing resonant nanocavity have been realized. Lee et al showed a colored ultrathin PV with subwavelength a-Si absorber below 30 nm embedded between two reflective metal electrodes (Figure 6g).…”