Physics Colloquium_

Prospects of low cost solar electricity with high efficiency flexible thin film solar cells based on compound semiconductors

Despite that within one hour our Earth receives enough solar radiation to meet the global energy demand for one year we are unable to tap the great potential of solar energy. Electricity is an expensive form of vital energy needed by mankind. Solar cells, which directly convert light into electricity, can provide clean and cost effective solar electricity in a sustainable manner. In this context, flexible and lightweight thin film solar cells offer numerous advantages for potentially low cost solar electricity generation. Low cost manufacturing of solar modules is linked to the inherent advantages of high speed roll-to-roll processing on polymer or metal foils, while high performance, flexibility and lightweight features of solar modules extend application related opportunities.

Optical and electronic properties of chalcopyrite compound semiconductors are attractive for solar cells. Hetero-junction devices based on polycrystalline Cu(In,Ga)Se2, called CIGS, have yielded 20.4% record efficiency cells on polymer film. This remarkably high efficiency – equal to the poly-Si wafer solar cell efficiency – on polymer film is achieved by overcoming different challenges in device processing and controlling parameters that contribute to optical and electronic losses in multi-layered device structure.

Controls of micro-structural and chemical properties of constituent layers and their adjacent interfaces on nano-scale are important in addition to impurities which could be detrimental or beneficial in CIGS. Composition gradient (energy band gap engineering) and passivation of electronic defects in CIGS need careful optimization for high efficiency flexible solar cells.

Laser patterning technology has been developed and monolithically interconnected flexible mini-modules of 16% efficiency have been achieved. The talk will provide insights into the development of 20.4% record efficiency flexible solar cells and discuss potentials for further improvements as well challenges for cost effective applications of high efficiency flexible CIGS solar modules.

Next Colloquiums

• Wednesday, 16 October 2013 Prof. Jochen Gemmer, Limpertsberg, 16h00 Tbc

• Wednesday, 23 October 2013 Prof. Ayodhya Tiwari, Belval, 16h00 Prospects of low cost solar electricity with high efficiency flexible thin film solar cells based on compound semiconductors

• Wednesday, 30 October 2013 Prof. Johan Pohl, Belval, 16h00 Intrinsic Point Defects in CuInSe2 and CuGaSe2 Studied by Screened-Exchange Hybrid Density Functional Theory

• Wednesday, 13 November 2013 Dr. Javier Campo, Limpertsberg Neutron Scattering Studies of Molecule Based Magnets

• Wednesday, 20 November 2013 Prof. Rainer Birringer, Limpertsberg Tbc

• Wednesday 4 December 2013 Prof. Wübbenhorst, Limpertsberg Tbc

• Wednesday, 18 December 2013 Dr. Charles Dewhurst, Limpertsberg Small-Angle Neutron Scattering – Instrumentation and Scattering from Magnetic and Superconducting materials

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