Monitoring water vapour penetration using a contactless technique

Some layers of thin film photovoltaic modules maybe critically sensitive to moisture. In this study we present a new tool for monitoring the effect of moisture using a particular Transparent Conductive Oxide (TCO) as a sensor. The moisture content of the encapsulant was determined by Fourier Transform Infra Red (FTIR) spectroscopic measurements. The TCO resistivity was measured using an inductive method. The different spectroscopic results show that the diffusion of water vapour in the encapsulant used in this study is in good agreement with Fick’s law and correlate well with the increase of resistivity of the TCO. However, the transport measurements bring evidence for a degradation of the TCO resistivity undetectable by conventional FTIR measurements

Optimization of ZnO Front Electrodes for High-Efficiency Micromorph Thin-Film Si Solar Cells

The quest for increased performances in thin film silicon Micromorph tandem devices nowadays requires an increase of current density. This can be achieved with thin cells by combining both a robust cell design and efficient light management schemes. In this work we identify three key requirements for the transparent conductive oxide electrodes. Firstly, strong light scattering into large angles is needed on the entire useful wavelength range: a front electrode texture with large enough features is shown to grant a high total current (typically >26 mA/cm2 with a 2.4 μm thick absorber material) while sharp features are reported to allow for high top cell current (>13 mA/cm2) and reduced reflection at the ZnO/Si interface. Secondly, sufficiently smooth substrate features are needed to guarantee a high quality of the silicon active material, ensuring good and stable electrical properties (typically Voc around 1.4 V). Thirdly, conduction and transparency of electrodes must be cleverly balanced, requiring high TCO mobility (~50 cm2/V/s) to maintain the sheet resistance below 30 Omega/sq while keeping absorption as low as possible. Optimization of these three key requirements using ZnO electrodes allowed us to realize high efficiency Micromorph devices with 13.5% initial and 11.5% stabilized efficiency

Solid on liquid deposition

A process for the deposition of a solid layer onto a liquid is presented. The polymer poly-di-chloro-para-xylylene, also known as Parylene C, was grown on low vapour pressure liquids using the conventional low pressure chemical vapour deposition process. A reactor was built and a process developed to enable the deposition of Parylene C at atmospheric pressure over high vapour pressure liquids. It was used to deposit Parylene C over water among others. In all cases Parylene C encapsulated the liquid without influencing its initial shape. The results presented here show also that the Parylene C properties are not affected by its growth on liquid templates and the roughness of the Parylene C surface in contact with the liquid during the deposition is extremely low