This thesis focuses on the optimization of silicon heterojunction (SHJ) solar cells. The main investigation regards hydrogenated amorphous silicon (a-Si:H) layer depositions and their influence on the solar cell performance. Therefore SHJ solar cells with different deposition parameters for the a-Si:H layers were fabricated and analysed in this work. We find that the thickness of the intrinsic and (p)-doped a-Si:H layers deeply influences the quality of passivation and the transport properties. An optimal (i)a-Si:H thickness of 8.7-15 nm has been found for textured surfaces and for (p)a-Si:H. We find optimal gas flux parameters for the deposition of the (p)a-Si:H layer. We present a rough model to calculate the conductivity of the (i)a-Si:H layer. We find that these conductivities are injection dependent. The model also allows us to calculate the (excess) carrier concentration in the (i)a-Si:H layers. We observe that an H2 plasma post treatment does not improve the passivation quality of our cells and that an HF treatment does not exclude oxygen bondings in the amorphous silicon network.

http://tesi.cab.unipd.it/39643/1/CanossaSofia_593829.pdf

The chemistry of clay-organic reactions

Universita' degli studi di padova facolta' di ingegneria

https://iopscience.iop.org/article/10.1088/1742-6596/1349/1/012048/pdf

Morphology and mechanical properties of polylactide/montmorillonite composites

This paper performs molecular dynamics simulations to investigate the role of the monovalent cations K, Na and the divalent cation Ca on the stability and swelling of montmorillonite. The recently developed CLAYFF force field is used to predict the basal spacing as a function of the water content in the interlayer. The simulations reproduced the swelling pattern of these montmorillonites, suggesting a mechanism of their hydration different (K + < Na + < Ca 2+ ) from that of K + -, Na + -, and Ca 2+ -montmorillonites. In particular, these results indicate that the valence of the cations has the larger impact on the behaviour of clay–water systems. It also finds that the differences in size and hydration energy of K + , Na + and Ca 2+ ions have strong implications for the structure of interlayer. This leads to the differences in the layer spacings of the simulated K + -, Na + -, and Ca 2+ -montmorillonites. Furthermore, these simulations show that the K cations interact strongly with the clay sheets for the dehydrated clay sheets, but for the hydrated clays the Ca cations interact clearly strongly with the clay sheets.

and hydration of interlayer cations: a molecular dynamics simulation

The selectivity of some reactions of substituted 1,2-glycols adsorbed in the interlayer space of layer silicates (homoionic montmorillonites) has been studied. By thermal treatment, pinacol rearranges quantitatively to pinacolone in the intracrystalline environment of these solids, the reaction being clearly preferred to the intramolecular dehydration. In the same way 2,3-diphenyl-2,3-butanediol gives two ketones, the reaction being also different from that taking place in homogeneous conditions. The extent and the selectivity of both reactions have been correlated with the acidity of the interlayer cations.

Intracrystalline Pinacol Rearrangement in Layer Silicates

The US Bureau of Mines is using Fourier-transform infrared (FT-IR) analysis to investigate the bonding mechanism that occurs during the dewatering of clay slurries. High-molecular-weight polymers are used as flocculating agents in these processes. This investigation presents the results of an FT-IR study of calcium-exchanged montmorillonite treated with polyacrylamide (PAM) and polyethylene oxide (PEO). Both thin film and attenuated total reflectance (ATR) spectroscopic techniques were employed to study this clay-polymer system. Results suggest PAM is adsorbed to the clay via the nitrogen atom of the polymer. A water bridge is involved in the bonding between the clay and PEO. Evidence also suggests that PEO may be adsorbed directly onto the surface of the clay.

The chemistry of clay-organic reactions

Citations

Universita' degli studi di padova facolta' di ingegneria

Morphology and mechanical properties of polylactide/montmorillonite composites

and hydration of interlayer cations: a molecular dynamics simulation

Intracrystalline Pinacol Rearrangement in Layer Silicates

An FT-IR study of calcium-exchanged montmorillonite treated with polyacrylamide and polyethylene oxide

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