ANNEALING OF POLYCRYSTALLINE THIN FILM SILICON SOLAR CELLS IN WATER VAPOUR AT SUB-ATMOSPHERIC PRESSURES

Thin film polycrystalline silicon (poly-Si) solar cells were annealed in water vapour at pressures below atmospheric pressure. PN junction of the sample was contacted by measuring probes directly in the pressure chamber filled with steam during passivation. Suns-VOC method and a Lock-in detector were used to monitor an effect of water vapour to VOC of the solar cell during whole passivation process (in-situ). Tested temperature of the sample (55°C – 110°C) was constant during the procedure. Open-circuit voltage of a solar cell at these temperatures is lower than at room temperature. Nevertheless, voltage response of the solar cell to the light flash used during Suns-VOC measurements was good observable. Temperature dependences for multicrystalline wafer-based and polycrystalline thin film solar cells were measured and compared. While no significant improvement of thin film poly-Si solar cell parameters by annealing in water vapour at under-atmospheric pressures was observed up to now, in-situ observation proved required sensitivity to changing VOC at elevated temperatures during the process

Synthesis, structure, and opto-electronic properties of organic-based nanoscale heterojunctions

Enormous research effort has been put into optimizing organic-based opto-electronic systems for efficient generation of free charge carriers. This optimization is mainly due to typically high dissociation energy (0.1-1 eV) and short diffusion length (10 nm) of excitons in organic materials. Inherently, interplay of microscopic structural, chemical, and opto-electronic properties plays crucial role. We show that employing and combining advanced scanning probe techniques can provide us significant insight into the correlation of these properties. By adjusting parameters of contact- and tapping-mode atomic force microscopy (AFM), we perform morphologic and mechanical characterizations (nanoshaving) of organic layers, measure their electrical conductivity by current-sensing AFM, and deduce work functions and surface photovoltage (SPV) effects by Kelvin force microscopy using high spatial resolution. These data are further correlated with local material composition detected using micro-Raman spectroscopy and with other electronic transport data. We demonstrate benefits of this multi-dimensional characterizations on (i) bulk heterojunction of fully organic composite films, indicating differences in blend quality and component segregation leading to local shunts of photovoltaic cell, and (ii) thin-film heterojunction of polypyrrole (PPy) electropolymerized on hydrogen-terminated diamond, indicating covalent bonding and transfer of charge carriers from PPy to diamond

A curve template for I-V characteristics of the solar cells

The contribution describes a computer program for manual fitting a theoretical dependence of the current flowing through a solar cell on the voltage in a way corresponding to flexible curve templates. The template provides handles "attached" to the curve for intuitive and independent manipulation of the parameters. This makes it possible to judge the sensitivity of the fit to the individual parameters

Thin films for photovoltaics deposited by plasma chemistry methods\n

Thin films are key components for practically all of contemporary photovoltaic cells for solar energy utilization. Cells use thin films for optimizing light trapping, for selecting and collection of photogenerated charges and interface passivation or as absorber layers. Each year several hundreds of square kilometers of thin films are deposited mainly by plasma chemistry methods

Object oriented programming of experiments in laboratory

A system for object oriented programming of experiments in laboratory was developed using Object Pascal vased on the component architecture of Delphi environment, which will be published as a open source project

Nanoscale characterization of ultra-thin tungsten films deposited by radio-frequency magnetron sputtering

In this article, atomic force microscopy was used for nanoscale characterization of ultra-thin tungsten films which were deposited on silicon substrate. Radio-frequency magnetron sputtering was used for tungsten deposition on the surface. © 2015 IEEE

Vývoj a výzkum nízkonákladové technologie fotovoltaických článků

Projekt se zabývá problematikou obnovitelných zdrojů energie, specificky fotovoltaiky. Tato zpráva pak sumarizuje průběh práce a dosažené výsledky řešení projektu. Navrhovaný projekt si klade za cíl vytvořit a využít potenciál vědeckých pracovníků v ČR zabývajících se tematikou fotovaltaiky. V rešeršní části zpráva sumarizuje výzkumné aktivity na poli fotovoltaiky nejen v Evropě, ale v celosvětovém měřítku

Direct measurement of optical losses in plasmon-enhanced thin silicon films (Conference Presentation)

Plasmon-enhanced absorption, often considered as a promising solution for efficient light trapping in thin film silicon solar cells, suffers from pronounced optical losses i.e. parasitic absorption, which do not contribute to the obtainable photocurrent. Direct measurements of such losses are therefore essential to optimize the design of plasmonic nanostructures and supporting layers. Importantly, contributions of useful and parasitic absorption cannot be measured separately with commonly used optical spectrophotometry. In this study we apply a novel strategy consisting in a combination of photocurrent and photothermal spectroscopic techniques to experimentally quantify the trade-off between useful and parasitic absorption of light in thin hydrogenated microcrystalline silicon (μc-Si:H) films incorporating self-assembled silver nanoparticle arrays located at their rear side. The highly sensitive photothermal technique accounts for all absorption processes that result in a generation of heat i.e. total absorption while the photocurrent spectroscopy accounts only for the photons absorbed in the μc-Si:H layer which generate photocarriers i.e. useful absorption [1]. We demonstrate that for 0.9 μm thick μc-Si:H film the optical losses resulting from the plasmonic light trapping are insignificant below 730 nm, above which they increase rapidly with increasing illumination wavelength. For the films deposited on nanoparticle arrays coupled with a flat silver mirror (plasmonic back reflector), we achieved a significant broadband enhancement of the useful absorption resulting from both surface texturing and plasmonic scattering, and achieving 91% of the theoretical Lambertian limit of absorption