The “Micromorph” cell: a new way to high-efficiency-low-temperature crystalline silicon thin-film cell manufacturing?

Abstract

Abstract. Hydrogenated microcrystalline Silicon (µc-Si:H) produced by the VHF-GD (Very High Frequency Glow Discharge) process can be considered to be a new base material for thin-film crystalline silicon solar cells. The most striking feature of such cells, in contrast to conventional amorphous silicon technology, is their stability under lightsoaking. With respect to crystalline silicon technology, their most striking advantage is their low process temperature (220°C). The so called "micromorph" cell contains such a µc-Si:H based cell as bottom cell, whereas the top-cell consists of amorphous silicon. A stable efficiency of 10.7% (confirmed by ISE Freiburg) is reported in this paper.At present, all solar cell concepts based on thin-film crystalline silicon have a common problem to overcome: namely, too long manufacturing times. In order to help in solving this problem for the particular case of plasma-deposited µc-Si:H, results on combined argon /hydrogen dilution of the feedgas (silane) are presented. It is shown that rates as high as 9.4 Å/s can be obtained; furthermore, a first solar cell deposited with 8.7 Å/s resulted in an efficiency of 3.1%.

Optimization of the performance of micromorph tandem solar cell a-Si/uc-Si

“…First concept was a-Si/a-SiGe but, as the cost of the Ge precursors is high and the electronic quality of the a-SiGe:H layers is lower than for a-Si:H layers, a lot of effort is being done in replacing the a-SiGe:H part of the cell by other solutions like microcrystalline Si [6]. This leads to the 'micromorph' cell concept combining an a-Si:H top cell with a microcrystalline Si bottom cell [1] as shown in Figure 1.…”

Experimental and simulation study of thin film silicon solar cells with intermediate reflector

“…Hydrogenated amorphous (a-Si:H) and microcrystalline ( c-Si:H) silicon are well suited for combination in a tandem solar cell [1][2][3]. An essential requirement for high efficiency is a good current matching as the cell with lower current limits the whole device.…”

Hydrogenated Microcrystalline Silicon for Photovoltaic Applications

“…The case of the 7.5% is more complicated. In this series, σ dark is strongly influenced by the oxygen content which varies from 3x10 19 (20 W sample) to 7x10 18 cm -3 (70 W sample). At these very high level of oxygen contamination, it is quite surprising that corresponding cells incorporating the same i-layer can still behave satisfactorily (see Fig.…”

“…silane dilution and plasma power (or the resulting deposition rate). On the other hand, it has been shown that these structural parameters (preferential orientation and columnar structure) can be controlled, in specific cases (for example using an argon and hydrogen dilution of silane), by the deposition conditions [19]. [20,21].…”