Silicon thin-film solar cells based on microcrystalline silicon (mu c-Si:H) were prepared in a 30 x 30 cm(2) plasma-enhanced chemical vapor deposition reactor using 13.56 or 40.68 MHz plasma excitation frequency. Plasma emission was recorded by optical emission spectroscopy during mu c-Si:H absorber layer deposition at deposition rates between 0.5 and 2.5 nm/s. The time course of SiH* and H-beta emission indicated strong drifts in the process conditions particularly at low total gas flows. By actively controlling the SiH4 gas flow, the observed process drifts were successfully suppressed resulting in a more homogeneous i-layer crystallinity along the growth direction. In a deposition regime with efficient usage of the process gas, the mu c-Si:H solar cell efficiency was enhanced from 7.9% up to 8.8% by applying process control. (C) 2007 Elsevier B.V. All rights reserved.

Instalacion de revestimiento, especialmente instalacion de revestimiento por PECVD, que comprende una camara de proceso y un sistema de conduccion de gas (1) para el suministro y/o la evacuacion de un gas ao de la camara de proceso de la instalacion de revestimiento, presentando el sistema de conduccion de gas (1) al menos una abertura de alimentacion (2) para alimentar gas al sistema de conduccion de gas (1) o para evacuar gas del sistema de conduccion de gas (1), al menos dos aberturas de salida (4a, 4b, 4c, 4d, 4e, 4f) para evacuar el gas del sistema de conduccion de gas (1) o para introducir el gas en el sistema de conduccion de gas (1), asi como conductos (3a, 3b, 3aa, 3ab, 3ac, 3ba, 3bb, 3bc) dispuestos respectivamente entre la al menos una abertura de alimentacion (2) y las aberturas de salida (4a, 4b, 4c, 4d, 4e, 4f), estando configurados los conductos (3a, 3b, 3aa, 3ab, 3ac, 3ba, 3bb, 3bc) de tal forma que la resistencia al flujo de los conductos (3a, 3b, 3aa, 3 ab, 3ac, 3ba, 3bb, 3bc) entre la al menos una abertura de alimentacion (2) y las aberturas de salida (4a, 4b, 4c, 4d, 4e, 4f) es sustancialmente igual, caracterizada porque el sistema de conduccion de gas (1) presenta al menos un punto de ramificacion (2a, 2b), en el que un primer tramo de conducto (3a, 3b) desemboca en al menos tres segundos tramos de conducto (3a, 3b, 3aa, 3ab, 3ac, 3ba, 3bb, 3bc) dispuestos a continuacion del primer tramo de conducto (3a, 3b).

Highly conductive and transparent aluminum-doped zinc oxide (ZnO:Al) films were prepared by reactive mid-frequency (MF) magnetron sputtering at high growth rates. By varying the deposition pressure, pronounced differences with respect to film structure and wet chemical etching behavior were obtained. Optimized films develop good light-scattering properties upon etching leading to high efficiencies when applied to amorphous (a-Si:H) and microcrystalline (μc-Si:H) silicon-based thin-film solar cells and modules. Initial efficiencies of 7.5% for a μc-Si:H single junction and 9.7% for an a-Si:H/μc-Si:H tandem module were achieved on an aperture area of 64 cm2.

Thin-film silicon solar cells with up to 11.2% stable cell efficiency have been developed on ZnO coated glass substrates on laboratory scale using solely plasma enhanced chemical vapour deposition (PECVD) and magnetron sputtering as deposition techniques for all thin films. To transfer this concept towards large areas, we developed a novel PECVD electrode which proved its capability of providing homogenous amorphous and microcrystalline silicon films on ∼1 m2 sized substrates. Microcrystalline silicon (μc-Si:H) solar cells were realised with efficiencies up to 7.2%. The high open-circuit voltage Voc and fill factor FF of 520 mV and 71%, respectively, demonstrate that high quality μc-Si:H material can be prepared with this large area electrode. Note that finally the entire thin-film structure–including all silicon, TCO and metal films–can be produced using one single equipment platform which complies with the requirements for a cost-effective and large scale mass production.

This contribution discusses recent scientific and technological challenges for the development of highly efficient microcrystalline silicon (mu c-Si:H) based thin film solar cells. Aluminium doped ZnO films prepared by sputtering and post deposition etching serve as transparent conductive oxide (TCO) material, which provide excellent light trapping properties. Challenges are the transfer of this approach to cost-effective reactive sputtering from metallic targets and the reduction of optical absorption losses in the front TCO films. We developed mu c-Si:H i-layers by plasma-enhanced chemical vapour deposition (PECVD) using 13.56 and 40.68 MHz excitation frequency, high deposition pressures and high RF-powers. These conditions provide sufficiently "soft" deposition for the growth of high quality mu c-Si:H material and yield high deposition rates. Stable aperture area module efficiencies of 10.1% and 8.1% were obtained for a-Si:H/mu c-Si:H and mu c-Si:H modules, respectively, on 10 x 10 cm(2) substrate size. Subsequent up-scaling to similar to 1 m(2) coating area was performed and a-Si:H/mu c-Si:H modules exceeding 10% initial aperture area efficiency were obtained. We discuss the questions of process stability and process reproducibility with respect to large area PECVD production systems. (c) 2006 Elsevier B.V All rights reserved.

The long term stability of non-encapsulated amorphous (a-Si:H) and microcrystalline (muc-Si:H) silicon single and tandem cell structures was tested by means of light soaking (AM 1.5, T=50 degC), damp heat testing (T=85 degC, humidity=85%) and high temperature treatment (T=150 degC) up to 2000 h to simulate a variety of harsh environmental conditions. In order to study the influence of the TCO front contact and backside contact on the long term stability, cells deposited on different substrates and prepared with different backside configurations were examined. As prepared (non-encapsulated) a-Si:H and muc-Si:H diodes show very similar effects after light soaking, damp heat testing and temperature treatment. Both solar cell types show no significant variation of the solar cell parameters even after 2000 h of damp heat testing. After light soaking a-Si:H diodes exhibit the well known distinct degradation of the fill factor while the bulk properties of the investigated muc-Si:H diodes remain nearly unchanged

This work addresses Applied Films (AF) work on the development of production equipment for silicon thin-film solar cells based on a tandem structure of amorphous silicon top and microcrystalline silicon bottom cells (a-Si:H/muc-Si:H) on glass substrates. Preceding work at the Institute of Photovoltaics (IPV) has demonstrated efficiencies >10% for a-Si:H/muc-Si:H modules on 30times30 cm2 substrate size. Recently, AF in close cooperation with the IPV succeeded to transfer the PECVD processes to a large area lab coater at AF and yielded initial efficiencies >10% for a-Si:H/muc-Si:H modules. Based on these results AF worked out a concept for mass production equipment for amorphous and microcrystalline silicon solar cells

We developed microcrystalline silicon (μc-Si:H) thin film solar modules on textured ZnO-coated glass. The single junction (p–i–n) cell structure was prepared by plasma-enhanced chemical vapour deposition (PECVD) at substrate temperatures below 250°C. Front ZnO and back contacts were prepared by sputtering. A process for the monolithic series connection of μc-Si:H cells by laser scribing was developed. These microcrystalline p–i–n modules showed aperture area efficiencies up to 8.3% and 7.3% on aperture areas of 64 and 676cm2, respectively. The temperature coefficient of the efficiency was −0.4%/K.