Project: DoIT

Title: "Development of an Optimised Integrated silicon Thin film solar module"

A Project funded by the European Community under the ‘FP5’ Programme (1998-2002) CONTRACT N° : ENK6-CT-2000-00321

Short Description: Development of an innovative silicon thin film solar 30x30cm2 module, consisting of an amorphous silicon/microcrystalline silicon tandem solar cell (micromorph cell) on TCO-coated glass substrate, exhibiting a stable module efficiency of 11% (active area). In view of industrial production, a deposition rate of at least 4 A/s will be achieved for the intrinsic microcrystalline silicon (µc-Si:H) layers.
The combination of the advantages of thin film technologies with the benefits of µc-Si:H and the up-scaling of the respective deposition processes are the main innovative points of the project. The project objectives are pursued along two different paths concerning the range of the plasma excitation frequency used for the deposition of µc-Si:H layers. The original experience in small-area micromorph laboratory cells has been gained with VHF; here, a lower deposition frequency range, including the usual frequency of 13.56 MHz, is added, for which the development of an optimized micromorph solar cell is also required. Most of the work, however, is devoted to the up-scaling of small-area recipes to large-area depositions in 30x30 cm2 Plasma Enhanced CVD reactors operating in both low frequency and VHF regimes. In both reactors the μc-Si:H deposition process is optimized to achieve sufficient uniformity and high deposition rates.

Plasma diagnostics and CFD modelling are applied for solving the problems related to power and gas consumption as well as deposition rate uniformity. Additional characterization methods are used to monitor structural, optical and electrical properties of the layers and cells, and to check the homogeneity of these properties over 30x30 cm2. Since the optimal performance of micromorph cells is crucially dependent on light trapping, the surface morphology of the TCO, as well as its electrical and optical properties are optimized. The characterization of different TCO materials is accompanied by optical modelling of the complete device. In view of a later expansion to larger-area modules (> 30x30 cm2), alternative TCO materials are also explored. Ultimately module fabrication is based on the best small-area test cells cut from 30x30 cm2 depositions. Here, the main task is the patterning of the functional cell layers by laser scribing and lift-off techniques in order to establish the monolithic series connection of cells.

So far, the development of micromorph tandems has reached highly homogeneous 11%±0.5 initial efficiency from 1 cm2 cells cut from 30x30 depositions.
The achievement of the project goals will potentially lead to >10% stabilized efficiency large area modules. Considering the possibility of achieving a cost/Wp similar to amorphous silicon, this technology can have a significant contribution to the goal of <1Euro/Wp.

Project Co-Ordinator: Plasma Technology Laboratory,   University of Patras (PTLUP)

Partners: Universite de Neuchatel (IMT), Forschungszentrum Julich,Institute for Photovoltaics (FZJ-IPV), RWE Solar GmbH, LPICM, Ecole Polytechnique Palaiseau, Institute of Physics of the Czech Academy of Sciences, Free Energy Europe SA.

Start Date: 1/1/2001                     

Duration: 36 Months

Total Budget: 3.88 M€