Intrinsic Amorphous Silicon Layer Research Articles

Optimization of ferroelectric liquid crystal optically addressed spatial light modulator performance

The switching mechanisms of ferroelectric liquid crystal optically addressed spatial light modulators (OASLMs) using a photosensitive structure made of an intrinsic amorphous silicon layer sandwiched in between an indium tin oxide coated glass sheet and a reflective metal layer are reviewed. Devices based on photoconductor and photodiode layers are briefly reviewed and attention is focused on pixelated metal mirror (PMM) devices, which offer fast switching and good optical characteristics with the same sensitivity range as the photodiode OASLMs. They are particularly suitable for high frame rate SLMs with intense read beams. Optimum drive conditions for this type of device are considered. An equivalent electrical circuit is proposed for the photosensitive structure and the voltage drop across the liquid crystal layer is investigated and related to the optical response of the device. Experimental work is carried out to demonstrate the validity of our equivalent circuit. We show that the synchronization of a light source with the case pulse enables the OASLM to work at frame rates of a few kilohertz. We also demonstrate that the exact synchronization of the write light source with the write pulse enhances the potential memory of the device.

Passivation properties of amorphous and microcrystalline silicon layers deposited by VHF-GD for crystalline silicon solar cells

A comparative study of crystalline silicon (c-Si) surface passivation techniques is presented. The passivation is essential in increasing the total solar cell efficiency by enhancing the open-circuit voltage ( V oc ). Apart from the thermally grown oxides or nitrides widely used sofar, recent publications report on excellent passivating properties of amorphous silicon (a-Si:H)- and microcrystalline silicon (μc-Si:H) layers, deposited on n-type crystalline silicon [1–3], forming thereby heterojunctions. We present first results of a new structure called ⪡BAP (Both Sides Amorphous Passivated) cell⪢, where the wafer was sandwiched between two intrinsic amorphous silicon layers. These two layers, as well as the μc-Si:H emitter, and the layer forming the BSF (Back Surface Field) were all deposited by the VHF-GD (Very High Frequency Glow-Discharge) process which was developed in our laboratory [4]. BAP cells showed V oc -values as high as 635 mV, proving thus the excellent passivating properties of a-Si:H and the validity of this cell concept which makes a fully in-line processing possible (wafer in-cell out).