FLEXIS: CIS thin film solar cells on flexible substrates

• Forschungsstelle: EU FRP
• Projektnummer: 97.0398
• Projekttitel Englisch: FLEXIS: CIS thin film solar cells on flexible substrates

Schlüsselwörter (Englisch)

Cu(In;Ga)Se2; CIGS; solar cells; thin films; photovoltaics; flexible solar cells; polymer

Alternative Projektnummern (Englisch)

EU project number: JOR3-CT98-0304

Forschungsprogramme (Englisch)

EU-programme: 4. Frame Research Programme - 5.1 Nonnuclear energies

Kurzbeschreibung (Englisch)

See abstract

Partner und Internationale Organisationen (Englisch)

Coordinator: ZSW, Baden-Württemberg (D)

Abstract (Englisch)

Thin film solar cells of Cu(In,Ga)Se2 (called as CIGS) are important for terrestrial applications because of high efficiency, stable performance and low cost potentials. The CIGS solar cells are also promising for space applications because of their excellent stability against high energy irradiation and potential to yield more than 1.5 kW/kg specific power (power to weight ratio).
The objective of this project was to develop lightweight and flexible solar cells on metal and polymer foils. The contributions our group (ETHZ) were directed towards: 1) low temperature (450 °C) growth of 'good' quality CIGS layers and solar cells, 2) investigation of different precursors for controlled incorporation of Na during the growth of CIGS layers, 3) development of high efficiency CIGS solar cells on polymers.
CIGS solar cells in the efficiency of up to 18.8% have been obtained on Mo/glass substrates. We have developed ~16% efficiency cells at ETHZ. For such high efficiency cells a certain amount of Na, which comes from the soda-lime glass substrate, and a high deposition temperature of ~555 °C are necessary to obtain an optimum carrier concentration and large grain size in the CIGS absorber layers. The layers grown at lower temperature and without Na, on polymer and metal substrates, yield low efficiency solar cels.
We have shown that NaF and NaCl precursors can be used as a source for Na doping in CIGS. The secondary ion mass spectroscopy (SIMS) measurements proved that Na can be incorporated in a controlled amount by controlling the temperature of NaF evaporation source during the co-evaporation of CIGS layers. With a low temperature (450 °C) deposition process we have developed 14% efficiency CIGS solar cells on glass substrates.
We have developed a novel process to obtain high efficiency CIGS solar cells on 10-25 mm thin polyimide films. About 2 mm thin CIGS absorber layers were grown at 450 °C by a co-evaporation method on polyimide layers which were spin coated on NaCl covered glass substrates. After the subsequent deposition of CdS buffer layer and ZnO/ZnO:Al transparent front contact, the NaCl buffer layer was dissolved in water to separate the ZnO/CdS/Cu(In,Ga)Se2/Mo/Polyimide stack from the glass substrate. A world record conversion efficiency of 12.8% (total area) under AM1.5 illumination was independently measured at FhG/ISE, Freiburg, Germany. This is the highest reported efficiency for any type of solar cell on polymer substrates.

Datenbankreferenzen (Englisch)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 97.0398