F. Friedrich

PECVD Intermediate and Absorber Layers Applied in Liquid-Phase Crystallized Silicon Solar Cells on Glass Substrates

Liquid-phase crystallized silicon absorber layers have been applied in heterojunction solar cells on glass substrates with 10.8% conversion efficiency and an open-circuit voltage of 600 mV. Intermediate layers of SiOx, SiNx, and SiOxNy, as well as the a-Si:H precursor layer, were deposited on 30 cm × 30 cm glass substrates using industrial-type plasma-enhanced chemical vapor deposition equipment. After crystallization on 3cm × 5cm area using a continuous-wave infrared laser line, the resulting polysilicon material showed high material quality with large grain sizes.

Controlling the thermal impact of ns laser pulses for the preparation of the P2 interconnect by local phase transformation in CIGSe

The thermal impact of nanosecond laser pulses was beneficially employed and well-controlled for the preparation of the P2 interconnect by local phase transformation (i.e., by drawing conductive lines rather than removing the material) in CIGSe mini-modules, which were demonstrated to outperform their conventionally needle-patterned counterparts. Conductivity and elemental composition of the scribed lines as well as the extent of the heat-affected area were analyzed, quantified and taken into account for achieving optimal CIGSe solar module performances. This approach opens new prospects for significant simplification of the serial interconnection, since the P2 und the P3 can be scribed simultaneously after deposition of both the CIGSe and the TCO layer.

Study on non-destructive identification of gallium concentration gradients in Cu(In, Ga)Se2 solar cells and their efficiency impact

The concentration gradient of gallium within the absorber layer is known to play an important role for the efficiency of Cu(In, Ga)Se2 solar cells. A promising method for their non-destructive analysis is angle-resolved x-ray fluorescence analysis. We present an investigation of the effect of different gallium concentration gradients on fundamental parameter-based calculations of the fluorescence spectra in comparison to their influence on the solar cell efficiency as derived by device simulations. The aim is to determine the ability of the analytical method to detect gradient variations relevant for solar cell performance.

Micro-contacting of single and periodically arrayed columnar silicon structures by focused ion beam techniques

Micron-sized, periodic crystalline Silicon columns on glass substrate were electrically contacted with a transparent conductive oxide front contact and a focused ion beam processed local back contact. Individual column contacts as well as arrays of >100 contacted columns were processed. Current-voltage characteristics of the devices were determined. By comparison with characteristics obtained from adapted device simulation, the absorber defect density was reconstructed. The contacting scheme allows the fabrication of testing devices in order to evaluate the electronic potential of promising semiconductor microstructures.

Testing and failure analysis of thin film solar cells

Elements of a systematic concept for test, characterization and analysis of thin film solar cells is discussed that is based on application and comparison of respective techniques in the world of micro- and nanoelectronic technologies, Starting with test and reliability issues, in depth electrical characterization like activation energy analysis from reverse dark currents, is presented. Analysis techniques that belong to the concept require electrically active devices and include all aspects of luminescence and stimulation. A key topic in electronic devices, Focused Ion Beam based Device or Circuit Edit, is also evaluated for application in thin film photovoltaics. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)