980 research outputs found
Dye sensitised solar cells with nickel oxide photocathodes prepared via scalable microwave sintering
No full textPhotoactive NiO electrodes for cathodic dye-sensitised solar cells (p-DSCs) have been prepared with thicknesses ranging between 0.4 and 3.0 mm by spray-depositing pre-formed NiO nanoparticles on fluorine-doped tin oxide (FTO) coated glass substrates. The larger thicknesses were obtained in sequential sintering steps using a conventional furnace (CS) and a newly developed rapid discharge sintering (RDS) method. The latter procedure is employed for the first time for the preparation of p-DSCs. In particular, RDS represents a scalable procedure that is based on microwave-assisted plasma formation that allows the production in series of mesoporous NiO electrodes with large surface areas for p-type cell photocathodes. RDS possesses the unique feature of transmitting heat from the bulk of the system towards its outer interfaces with controlled confinement of the heating zone. The use of RDS results in a drastic reduction of processing times with respect to other deposition methods that involve heating/calcination steps with associated reduced costs in terms of energy. P1-dye sensitized NiO electrodes obtained via the RDS procedure have been tested in DSC devices and their performances have been analysed and compared with those of cathodic DSCs derived from CS-deposited samples. The largest conversion efficiencies (0.12%) and incident photon-to-current conversion efficiencies, IPCEs (50%), were obtained with sintered NiO electrodes having thicknesses of B1.5–2.0 mm. In all the
devices, the photogenerated holes in NiO live significantly longer (th B 1 s) than have previously been reported for P1-sensitized NiO photocathodes. In addition, P1-sensitised sintered electrodes give rise to relatively high photovoltages (up to 135 mV) when the triiodide–iodide redox couple is used.Science Foundation IrelandKnut and Alice Wallenberg FoundationSwedish Energy AgencyRoyal Society for ChemistryAM
Reduced hysteresis and enhanced air stability of low-temperature processed carbon-based perovskite solar cells by surface modification
No full textLow temperature processed carbon-based perovskite solar cells (C-PSCs) have gained great interest because of low cost and ease of fabrication. By replacing the Au electrode with carbon, stable solar cells suited for mass-production process can be made. However, power conversion efficiencies (PCEs) of C-PSCs still lag behind that of PSCs with Au contact.Here we explore low temperature (<= 150 degrees C) processed C-PSCs with, where a two-step method is used to prepare mixed-ion lead perovskite films, with tin oxide (SnO2) electron transport layer, poly(3-hexylthiophene-2,5-diyl) (P3HT) hole transport layer and carbon electrode, resulting in devices with a PCE of 14.0%. Moreover, hexyl trimethylammonium bromide (HTAB) was introduced to improve the interface between perovskite and P3HT. Perovskite grains were remarkably enlarged into micrometer-size and defects were reduced. As a result, a champion PCE of 16.1% was obtained, mainly due to enhanced fill factor from 0.67 to 0.73. The interface modification by HTAB molecule is an effective way to passivate the perovskite defects and facilitate the carrier transport at the perovskite/HTL interface. Unencapsulated devices showed excellent stability over 1500 h stored under ambient air (relative humidity -50 +/- 10%)
Copper Complexes with Tetradentate Ligands for Enhanced Charge Transport in Dye-Sensitized Solar Cells
No full textIn dye-sensitized solar cells (DSCs), the redox mediator is responsible for the regeneration of the oxidized dye and for the hole transport towards the cathode. Here, we introduce new copper complexes with tetradentate 6,6′-bis(4-(S)-isopropyl-2-oxazolinyl)-2,2′-bipyridine ligands, Cu(oxabpy), as redox mediators. Copper coordination complexes with a square-planar geometry show low reorganization energies and thus introduce smaller losses in photovoltage. Slow recombination kinetics of excited electrons between the TiO2 and CuII(oxabpy) species lead to an exceptionally long electron lifetime, a high Fermi level in the TiO2, and a high photovoltage of 920 mV with photocurrents of 10 mA∙cm−2 and 6.2% power conversion efficiency. Meanwhile, a large driving force remains for the dye regeneration of the Y123 dye with high efficiencies. The square-planar Cu(oxabpy) complexes yield viscous gel-like solutions. The unique charge transport characteristics are attributed to a superposition of diffusion and electronic conduction. An enhancement in charge transport performance of 70% despite the higher viscosity is observed upon comparison of Cu(oxabpy) to the previously reported Cu(tmby)2 redox electrolyte
Slot-die coating of electron transport layers for perovskite solar cells using water and butanol-based tin oxide dispersions
No full textLead halide perovskite photovoltaics have shown an impressive efficiency increase over the past decade. Making this technology industrially viable requires precise optimization of every single deposition step. Here we used slot-die coating, a promising scalable deposition technique to enable large scale deposition. We demonstrate the challenges in developing high-quality slot-die coated tin oxide (SnO) films, suited as electron selective layers in perovskite solar cells. We studied the film quality of two commercially available colloidal SnO dispersions by controlling pump rate, coating speed and temperature of the indium tin oxide substrates (ITO). The water-based dispersion was more difficult to control, but resulted in better perovskite solar cell performance than the butanol-based dispersion. Hysteresis in J-V curves from the water-based tin oxide dispersion was reduced by potassium fluoride addition. A maximum power conversion efficiency of 17.5% was achieved for MAPbI-based solar cells by careful optimization of the deposition parameters
Course System Architecting for Management
No full textThis article describes the condensed version the course System Architecture by the Center for Technical Training CTT. Trainer is the author of this article Gerrit Muller. At this moment this course is only accessible for Philips Employees
Improving the Performance of Dye-Sensitized Solar Cells
No full textDye-sensitized solar cells have been investigated intensively during the last three decades. Nevertheless, there are still many aspects to be explored to further improve their performance. Dye molecules can be modified endlessly for better performance. For instance, steric groups can be introduced to slow down recombination reactions and avoid unfavorable aggregation. There is a need for more optimal dye packing on the mesoporous TiO2 surface to increase light absorption and promote a better blocking effect. Novel redox mediators and HTMs are key elements to reach higher performing DSC as they can offer much higher output voltage than the traditional triiodide/iodide redox couple
Photoinduced ultrafast dynamics of the triphenylamine-based organic sensitizer D35 on TiO2, ZrO2 and in acetonitrile.
No full textThe relaxation dynamics of the dye D35 has been characterized by transient absorption spectroscopy in acetonitrile and on TiO2 and ZrO2 thin films. In acetonitrile, upon photoexcitation of the dye via the S0 → S1 transition, we observed ultrafast solvation dynamics with subpicosecond time constants. Subsequent decay of the S1 excited state absorption (ESA) band with a 7.1 ps time constant is tentatively assigned to structural relaxation in the excited state, and a spectral decay with 203 ps time constant results from internal conversion (IC) back to S0. On TiO2, we observed fast (<90 fs) electron injection from the S1 state of D35 into the TiO2 conduction band, followed by a biphasic dynamics arising from changes in a transient Stark field at the interface, with time constants of 0.8 and 12 ps, resulting in a characteristic blue-shift of the S0 → S1 absorption band. Several processes can contribute to this spectral shift: (i) photoexcitation induces immediate formation of D35˙+ radical cations, which initially form electron–cation complexes; (ii) dissociation of these complexes generates mobile electrons, and when they start diffusing in the mesoporous TiO2, the local electrostatic field may change; (iii) this may trigger the reorientation of D35 molecules in the changing electric field. A slower spectral decay on a nanosecond timescale is interpreted as a reduction of the local Stark field, as mobile electrons move deeper into TiO2 and are progressively screened. Multiexponential electron–cation recombination occurs on much longer timescales, with time constants of 30 μs, 170 μs and 1.4 ms. For D35 adsorbed on ZrO2, there is no clear evidence for a transient Stark shift, which suggests that initially formed cation–electron (trap state) complexes do not dissociate to form mobile conduction band electrons. Multiexponential decay with time constants of 4, 35, and 550 ps is assigned to recombination between cations and trapped electrons, and also to a fraction of D35 molecules in S1 which decay by IC to S0. Differential steady-state absorption spectra of D35˙+ in acetonitrile and dichloromethane provide access to the complete D0 → D1 band. The absorption spectra of D35 and D35˙+ are well described by TDDFT calculations employing the MPW1K functional
An extraordinary photograph: Gerrit Rietveld, Mart Stam and El Lissitzky at the Schröder House, 1926
No full textThe Schröder House, designed in 1924 by Gerrit Th. Rietveld (1888-1964) in closecollaboration with the client Truus Schröder-Schräder (1889-1985), has beenphotographed countless times.1 Most of the photographs of this well-knownmonument are architectural photographs, of its exterior or interior. Only a fewof them include one or both of the designers. One such photograph, from 1926,appears in many publications concerning Rietveld or the Schröder House. It is anintriguing shot; but what exactly does it tell us?Heritage & Value
Gerrit Rietveld 's shop designs in the Netherlands from 1922 to 1962
No full textThis essay investigates the shops as well as commercial buildings designed by Gerrit Rietveld in the Netherlands from 1922 to 1962, focusing on the relation between the interior and the exterior in each project. Gaining insight into his contribution to the history of shop designs. This research has been conducted through a combination of literature study, and the archive of Gerrit Rietveld in the Het Nieuwe Instituut in Rotterdam, and provides elaboration on themes as the designs of the shop front, the interior, and the connection between them. These themes are addressed through observation of the images, and drawings in the archive and other resources. The essay also provides a critical view for the role of those shops in history, and their influences on subsequent shop designs after that. AR2A011Architecture, Urbanism and Building Science
The sense of God’s presence in prayer
No full textThe awareness of God’s presence and the experience of his works – key notions in practices of prayer – find reasonable doubt in our secular age. Meanwhile, there are, worldwide, many communities of faith where people enthusiastically pray and hold that they hear the voice of God. How can we understand this sense of God’s presence?
In prayer, people express their hope and fear, and they do so with heart and mind. This subjective involvement is characteristic for prayer. At the same time, supplicants address God in the conviction that God is present and active. Critics of religion, however, criticise this ‘external’ realm of the divine and consider prayer a superstitious delusion. Passages of William James and John Calvin help us to get some insight in the ‘object’ of our religious consciousness. Furthermore, William Alston defends a non-sensory mystical perception of the divine. Using these insights, the author explores prayer as a conversation with God and reflects on the notion: hearing the voice of God
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