Title: Mature CIGS-based solar cells technology
Area: 1 – High-performance Factories
Call topic: 1.2 – Innovative technologies for the carrying-out of components characterized by advanced functional features
Coordinating Institute: IMEM – Institute of materials for electronics and magnetism (Parma)
- IMEM – Institute of materials for electronics and magnetism (Trento)
- ISMN – Institute of nanostructured materials (Bologna)
Industrial Interest Group: Consorzio di Ricerca Hypatia (Rome)
Abstract: The “MaCISte” project aims to the solution of specific issues that hinders the industrial scale-up of a novel process for the deposition of thin-film solar cells based on Cu(In,Ga)Se2 (CIGS), by means of the Pulsed Electron Deposition (PED) technique. This technique, developed at the IMEM-CNR, allows the realization of solar cells with efficiencies > 15% on a laboratory scale.
The industrial transfer requires substantial changes of the deposition process and in particular on the PED sources, to increase the deposition rate and to make the process more easily controllable and compatible with the deposition on flexible substrates, which represent a tremendous opportunity for “building integrated photovoltaics” (BIPV).
The ultimate goal is the fabrication of a PED system prototype, to deposit CIGS films on a flexible substrates with characteristics compatible with the requirements of the companies supporting the project (PV efficiency >14% and increased and controlled deposition rate).
Ideas and solutions:
The following solutions have been adopted: i) selection and study of flexible substrates (polymers, metals, carbon fibers, etc) suitable for the growth of CIGS film by PED. Dedicated sample holder have been realized and tested. ii) automatic, real-time control of the growing film thickness (hardware & software) exploiting the heat radiation emitted from the film surface during the growth (optical interference), using a pyrometer controlled by a software. It worth noting to remind that conventional film thickness measurement systems (such as micro-balance) can not be used in an high energy pulsed environment (PED vacuum chamber). iii) High efficient PED customized sources have been realized by changing the conventional power supply circuits with solid state and gas HV switch (thyratron). The new device reproducibly works at frequencies as high as 50-100 Hz (vs. 10-15 Hz of the Neocera PED source). The shape and size have been re-designed to allow the installation of a multi-PED system to scale-up the deposition.
The conversion efficiency of the CIGS-based flexible solar cells realized within the MaCISte project are still rather low (best results are around 10%), also on small areas. The optimization (beyond the scopes of the present project) is in progress to solve the following issues: 1) The surface roughness is always worst that on glass. This imposes a careful control of the substrate metallization (back contact). 2) Substrate bending may lead to the CIGS peeling and cell degradation. 3) The control of the deposition uniformity over large area (and the interaction among different ”MaCISte” PED sources is still in progress).
The industrial partner (Consorzio Hypatia) that endorsed the submission of this proposal, confirmed the strong interest in this activity, both for the development of the PED technique and for the fabrication of thin film solar cells based on CIGS.
However, a clear requirement is to move from a static to a continuous deposition process. This is the aim of a new project (”Rolling CIGS”) funded in the framework of the Progetto Bandiera – Fabbrica del Futuro – Bando Prototipi, that will be also presented during the 30.BI-MU exhibition and that, in spite of the limited time ad disposal, enables the upgrade of the existing deposition system (deliverable of MaCISte) with a roll-to-roll substrate holder specially designed for flexible substrates, whose automatic movement is guided by the pyrometer film thickness measurement system (realized in MaCISte) to uniform the deposition.
From “MaCISte” (Progetto Bandiera -FdF- Sottoprogetto 1), to “Rolling CIGS” (Progetto Bandiera -FdF- Bando Prototipi)