Amorphous and Microcrystalline Silicon Solar Cells Grown by Pulsed PECVD Technique

Abstract

The Pulsed PECVD technique involves modulating the standard 13.56 MHz RF plasma, in the kHz range. This allows an increase in the electron density during the ‘ON’ cycle, while in the ‘OFF’ cycle neutralizing the ions responsible for dust formation in the plasma. In this work, we report the increase of i-layer growth rate and silane gas utilization rate (GUR) for amorphous Si p-i-n solar cells grown in a large area (30 cm × 40 cm) single chamber deposition system. The i-layer growth rate of 5.4 Å/sec with a GUR of >15% has been achieved, which shows a device efficiency of 8.3% (almost same as of our conventional PECVD grown a-Si:H solar cell with ilayer growth rate of ∼1 Å/sec). We also deposited microcrystalline Si p-i-n devices using the Pulsed PECVD technique. The crystallite orientation of the films changes from a random to a (220) orientation near the microcrystalline-to-amorphous transition. The effects of crystallite orientation, grain boundaries and ion bombardment during growth on the solar cell performances are investigated. An efficiency of 4.8% for single junction μc-Si:H p-i-n device has been achieved for the i-layer thickness of 0.9 μm.

Bottom-Gate TFTs with Channel Layer Grown by Pulsed PECVD Technique

“…Film 1 is deposited with no hydrogen dilution and low RF power and is thus amorphous. For films 2, 3, and 4, the SiH 4 flow rate and RF power were varied, in order to produce differing degrees of (220) or (111) grain orientation in the crystallites [2]. The 50 nm films are labelled 50-1, 50-2, 50-3, 50-4, and the 300 nm films are labelled 300-1, 300-2, 300-3, 300-4, where the suffix denotes the process conditions used.…”

“…In theory, it can provide equal or increased mobility and improved stability over its amorphous counterpart due to its crystallinity; however, in practice this is not always the case [1]. Recently, nc-Si:H films deposited by pulsed PECVD for use in solar cells have been reported [2]. Pulsed PECVD is the same as conventional PECVD at 13.56 MHz, except the plasma is modulated with a frequency in the kHz range.…”