I. Usatii

Silicon oxide based n-doped layer for improved performance of thin film silicon solar cells

We propose the use of n-doped silicon oxide as alternative n-layer in thin film Si p-i-n solar cells. By varying input gas ratios, films with a wide range of optical and electrical properties are obtained. Applying these layers in solar cells, good electrical and optical properties are demonstrated. A relative efficiency increase up to 13.6% has been observed on the cells adopting a simple Ag back contact. A similar spectral response as with the cell with standard n-layer plus ZnO/Ag back contact is obtained. The deposition of a buffer layer at the back contact can therefore be avoided.

Self-organized broadband light trapping in thin film amorphous silicon solar cells.

Nanostructured glass substrates endowed with high aspect ratio one-dimensional corrugations are prepared by defocused ion beam erosion through a self-organized gold (Au) stencil mask. The shielding action of the stencil mask is amplified by co-deposition of gold atoms during ion bombardment. The resulting glass nanostructures enable broadband anti-reflection functionality and at the same time ensure a high efficiency for diffuse light scattering (Haze). It is demonstrated that the patterned glass substrates exhibit a better photon harvesting than the flat glass substrate in p-i-n type thin film a-Si:H solar cells.

Plasmonic Light Trapping in Thin-Film Solar Cells: Impact of Modeling on Performance Prediction

We present a comparative study on numerical models used to predict the absorption enhancement in thin-film solar cells due to the presence of structured back-reflectors exciting, at specific wavelengths, hybrid plasmonic-photonic resonances. To evaluate the effectiveness of the analyzed models, they have been applied in a case study: starting from a U-shaped textured glass thin-film, µc-Si:H solar cells have been successfully fabricated. The fabricated cells, with different intrinsic layer thicknesses, have been morphologically, optically and electrically characterized. The experimental results have been successively compared with the numerical predictions. We have found that, in contrast to basic models based on the underlying schematics of the cell, numerical models taking into account the real morphology of the fabricated device, are able to effectively predict the cells performances in terms of both optical absorption and short-circuit current values.

MoOx as hole-selective collector in p-type Si heterojunction solar cells

We investigated the possible application of molybdenum oxide (MoOx) on the backside of p-type SHJ solar cells as substitute for the silicon-based back surface field layer. Solar cells with 4 cm2 area were fabricated on FZ c-Si(p) wafers, passivated with ultrathin i-a-Si:H buffers. A nanocrystalline n-SiOx emitter was applied while on the backside we applied 20 nm-thick p-type a-Si:H or evaporated MoOx (10 nm). Symmetric samples were additionally prepared to compare the effects on wafer passivation of MoOx versus the more conventional p-a-Si:H layer. For flat devices we have observed a Voc increase of ∼40 mV with MoOx replacing p-a-Si:H, with fill factors ∼73% in both the cases. Globally an efficiency increase of 1% absolute has been achieved moving to the MoOx hole collector. The feasibility of the MoOx/Ag backside configuration has been demonstrated also for textured p-type SHJ solar cells, reaching so far an efficiency of 18.1%.

Relevance Of TCO workfunction in n-silicon oxide emitter - c-Si (p) heterojunction solar cell

The amorphous /crystalline silicon heterojunction solar cells have largely demonstrated their usefulness to reach high efficiency. We have adopted a different and wider bandgap emitter based on silicon oxide, n-SiOx. A central role in this type of structure is played from the TCO workfunction whose value affects strongly the heterojunctions band structure at the emitter interface. RF magnetron sputtered TCO obtained with different deposition parameters, have been made in order to optimize their use in our heterojunction solar cell. Numerical simulation on the SiOx HJ, with TCO having proper workfunction value, show potential efficiency conversion well over the 23%. New Roman Bold font. An example is shown next.

Hybrid a-Si/nc-Si solar cells fabricated on a directly-deposited textured zinc oxide transparent conductor

This paper reports the development of a VHF PECVD process at 40.68 MHz for deposition of device-grade nc-Si:H. It further reports the evaluation of textured ZnO:Al films produced by hollow cathode sputtering as regards their suitability to serve as a TCO substrate for a-Si:H / nc-Si:H tandem device fabrication. The tandem devices were produced using an established VHF PECVD process at 100 MHz. Both VHF processes are capable of producing similar nc-Si:H material based on their analysis using micro-Raman spectroscopy. For the tandem junction devices, a peak in device efficiency was obtained at a Raman crystalline fraction of 50-52 % and a microstructure parameter of 0.60-0.68. A best tandem cell efficiency of 9.9% was achieved on HC ZnO compared to 11.3% on a reference Type-U SnO2 substrate.