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New approaches for materials and processes with low environmental impacts on the manufacturing of polycrystalline thin-film solar cells

Objective



Project Objectives

The major aims of this project are :

development of new buffer layers alternative to those based on cadmium compounds,
design and analysis of new preparation processes as alternative to the conventional chemical bath deposition methods which can provide more efficient raw material consumption and ease large-scale implementation, characterization of the thin-film properties of the buffer layers and assessment of their performance for photovoltaic solar cells, to develop and test a whole flow-sheet in order to demonstrate a recycling approach where all chemicals used in the CBD processes can be fully recovered, and undergo as proof-of-concept for any fabrication step of a polycrystalline-thin-film solar device.

While having in mind practical applications, the goals will be concurrently addressed at aw-material consumption, environmental impact of the processes, and adaptation to industrial technologies.


Technical Approach

The lowering costs of thin-film solar cells, as factor of success of these technologies, is strongly associated to the environmental implications of their practical use and large-scale dissemination. Prevention of pollution in any production process requires to pay attention to several aspects such as, mainly:

choice of inherently safer or environmentally more benign materials; process design;
plant configuration;
human resources;
research and development.

The project will consist of four work packages to be executed by an integrated consortium which brings together a recognized European PV-company and R&D centers having expertise in all relevant fields involved: laboratory preparation of photovoltaic thin film materials, waste treatments and recycling, process engineering, and industrial implementation. These work packages address the fundamental research issues of alternative materials, new production processes, waste and chemicals treatment, and analysis of environmental impacts.

Expected achievements and exploitation

During the first six months of the project all work packages have started-up their activities. CIEMAT has developed a blocking layer, as alternative window for thin-film solar cells, by a sol-gel process with a considerable antireflecting effect, up-to a 14% of increase of light transmission through the window. Also hydroxy-sulphide thin films have been prepared by CBD up-to areas of 15x30 cm2. First assessment experiments for electrodeposition of CdTe onto these layers have been carried out by BP Solar with encouraging results. Concerning to the activities on process for a more efficient raw material consumption BP Solar has provided a new formulation for CdS-CBD, where reagent usage can be reduced by 80-90%. Recycling experiments conducted by ECP/CRSA have showed that Cd recovery from CBD process effluents until the 1 ppm limit is possible by an electrochemical method. First attempts on the utilization of extraction/stripping methods point out that Cd recovery can be possible until the range of 0.5-0.05 ppm. An experimental set-up capable of investigating the formation of CdS thin films by a continuous recirculation of the reacting solution has been designed an constructed by CPERI. Concerning the environmental impact of the processes a risk assessment of substances hazardous to human health and the environment is beeing carried out by UNN-NPAC.


Work in the coming project period will center on the same topics but will increase in depth. Particular emphasis will be placed on the development and optimization of alternative windows for thin-film solar cells. Work on recycling will focus on the separation of colloids and recovery of soluble chemicals after a CBD process. Additional emphasis will be placed on developing the continuous recirculating reactor. An experimental set-up will be designed to quantify emission levels.

Exploitation of the results is based on the utilization of compound with low environmental impacts, and the optimization of raw material and recycling of active materials, which have to help the industry in waste management with a subsequent reduction of the cost.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
Address
22,Avenida Complutense 22
28040 Madrid
Spain

Participants (4)

BP SOLAR LTD
United Kingdom
Address
Chertsey Road
TW167XA Sunbury-on-thames
CENTRALE RECHERCHE SA
France
Address
Grande Voie Des Vignes, Ecole Centrale Paris
92295 Chatenay Malabry
FOUNDATION OF RESEARCH AND TECHNOLOGY - HELLAS
Greece
Address
6Th Km, Charilaou - Thermi Road
57001 Thessaloniki
University of Northumbria at Newcastle
United Kingdom
Address
Ellison Place
NE1 8ST Newcastle Upon Tyne