This release is available in German.
High-performance flexible and lightweight solar cells, say, on plastic foils, have excellent potential to lower the manufacturing costs through roll-to-roll processing and the so called "balance-of-system" cost, thus enabling affordable solar electricity in the near future. Thus far, however, flexible solar cells on polymer films have been lacking behind in performance compared to rigid cells, primarily because polymer films require much lower temperatures during deposition of the absorber layer, generally resulting in much lower efficiencies.
The research team at Empa's Laboratory for Thin Film and Photovoltaics, led by Ayodhya N. Tiwari, has been involved in the development of high-efficiency CIGS solar cells on both glass and flexible substrates with a special focus on reducing the deposition temperature of the CIGS layer. The group has repeatedly increased efficiency of flexible CIGS solar cells over the past years first at ETH Zurich and now since three years at Empa. With their current record value of 18.7% Tiwari and his team nearly closed the efficiency gap to cells based on multi-crystalline silicon (Si) wafers or CIGS cells on glass. The scientific details of their novel low-temperature deposition technology and the multi-layered device have recently been published in Nature Materials.
"To achieve such high efficiency values, we had to reduce the recombination losses of photo-generated charge carriers", said Tiwari. CIGS layers grown by co-evaporation at temperature of around 450 C have a strong composition grading because of inadequate inter-diffusion of intermediate phases and preferential diffusion of gallium (Ga) towards the electrical back contact.
To overcome this problem doctoral students Adrian Chirilă and Patrick Bloesch d
|Contact: Dr. Ayodhya N. Tiwari|
Swiss Federal Laboratories for Materials Science and Technology (EMPA)