Search query: DSCs

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abstract: Deploying earth abundant copper as a redox mediator in dye sensitized solar cells (DSCs) has been found to be a very promising strategy to achieve higher photovoltage and power conversion efficiencies in full sun (100 mW cm 2) and in low/diffuse light conditions. Achieving higher photovoltage without compromising photocurrent helped copper electrolyte attract considerable attention among alternate electrolytes currently employed in DSCs. The very small reorganization energy between Cu(I) and Cu(II) and small molecular size helped copper achieve unit regeneration efficiency, with a driving force as low as 100 mV and a high diffusion coefficient (Dn) leading to better diffusion length (Ln) and charge collection efficiency (ecc) Mass transport issues were also found to be improved for copper electrolytes in comparison with cobalt electrolytes. As it is inert to silver and other electrical contacts used in DSCs and possesses higher mobility even in solid state, copper based electrolyte is a promising candidate to spearhead the commercialization of dye solar technology. In this regard, a detailed evaluation of internal electron transfer dynamics is highly essential to understand the limiting processes in these devices. In the present study, we performed a comparison between copper, cobalt and iodine electrolytes using the same dye (LEG4) semiconductor (TiO2) and additive concentrations to understand in detail the charge transfer processes leading to higher photoconversion efficiencies and also probe the various deleterious processes taking place in copper devices that provide opportunities to further improve its performance in future.
author_names: Sourav Pradhan

Anders Hagfeldt

Suraj Soman
title: Resurgence of DSCs with copper electrolyte: a detailed investigation of interfacial charge dynamics with cobalt and iodine based electrolytes
year: 2018

abstract: Iodine binding to thiophene rings in dyes for dye sensitized solar cells (DSCs) has been hypothesized to be performance degrading in a number of literature cases. Binding of iodine to dyes near the semiconductor surface can promote undesirable electron transfers and lower the overall efficiency of devices. Six thiophene or furan containing dye analogs were synthesized to analyze iodine binding to the dyes via Raman spectroscopy, UV Vis studies, device performance metrics and density functional theory (DFT) based computations. Evidence suggests I2 binds thiophene based dyes stronger than furan based dyes. This leads to higher DSC device currents and voltages from furan analogues, and longer electron lifetimes in DSC devices using furan based dyes. Raman spectrum of the TiO2 surface bound dyes reveals additional and more instense peaks for thiophene dyes in the presence of I2 relative to no I2. Additionally, broader and shifted UV Vis peaks are observed for thiophene dyes in the presence of I2 on TiO2 films suggesting significant interaction between the dye molecules and I2. These observations are also supported by DFT and TD DFT calculations which indicate the absence of a key geometric energy minimum in the dye I2 ground state for furan dyes which are readily observed for the thiophene based analogues.
author_names: Alexandra Baumann

Hammad Cheema

Md Abdus Sabuj

Louis E McNamara

Yanbing Zhang

Adithya Peddapuram

Suong T T Nguyen

Davita L Watkins

Nathan I Hammer

Neeraj Rai

Jared H Delcamp
title: Iodine binding with thiophene and furan based dyes for DSCs.
venue: Physical chemistry chemical physics PCCP
year: 2018

abstract: Thieno[3,4 b]pyrazine (TPz) is examined as an electron deficient p bridge enabling near infrared (NIR) spectral access in dye sensitized solar cells (DSCs) Seven dissymmetric dyes for DSCs were synthesized (NL2 NL8) with TPz as the p bridge utilizing palladium catalyzed C H activation methodology. C H bond cross coupling was uniquely effective among the cross couplings and electrophilic aromatic substitution reactions analyzed in monofunctionalizing the TPz building block. The TPz based NL2 NL8 dyes examine the effects of various donors, p spacers, and acceptors within the donor p bridge acceptor (D p A) dye design. Proaromatic TPz stabilizes the excited state oxidation potential (E(s+/s* of the dyes by maintaining aromaticity upon excitation of the dye molecule. This leads to concise conjugated systems capable of accessing the NIR region. Through judicious structural modifications, dye band gaps were reduced to 1.48 eV, and power conversion efficiencies (PCEs) reached 7.1% in this first generation TPz dye series.
author_names: Nalaka P Liyanage

Aswani Yella

Mohammad Khaja Nazeeruddin

Michael Gratzel

Jared H Delcamp
title: Thieno[3,4 b]pyrazine as an Electron Deficient p Bridge in D A p A DSCs.
venue: ACS applied materials interfaces
year: 2016

abstract: Sequential series multijunction dye sensitized solar cells (SSM DSCs) which are mechanically stacked single illuminated area DSC devices wired in series, are reported to have exceptionally high photovoltages (Voc) ranging from 1.9 4.7 V from 2 5 stacked subcells. The use of multiple photoactive films under one area within the SSM DSC framework is made possible by fine tuning the thickness of TiO2 in each device and by judicious dye selection to allow for excellent light distribution among the films, termed as "photon management" The SSM DSC approach allows for incorporation of materials designed to use the maximal potential energy of photons in each region of the solar spectrum. Importantly, SSM DSCs were observed to maintain high Voc under low light conditions, rendering these systems very attractive for indoor applications. Additionally, an SSM DSC was found to have a solar to fuel conversion efficiency of 2% (2.7% including H2 production) for the reduction of CO2 to CO with IrO2 and Au2O3 electrocatalysts, without an external bias.
author_names: Hammad Cheema

Roberta R Rodrigues

Jared H Delcamp
title: Sequential series multijunction dye sensitized solar cells (SSM DSCs) 4.7 volts from a single illuminated area
year: 2017

abstract: A modular approach based on Suzuki Miyaura cross coupling and Miyaura borylation has been used to prepare two cyclometallated [Ru(N^N)2(C^N) complexes which possess either a carboxylic or phosphonic acid group attached via a phenylene spacer to the 4 position of the pyridine ring in the C^N ligand. The key intermediate in the synthetic pathway is [Ru(bpy)2(1) where bpy 2,2' bipyridine and H1 is 4 chloro 2 phenylpyridine. The crystal structure of [Ru(bpy)2(1)[PF6] is presented. Reaction of [Ru(bpy)2(1)[PF6] with 4 carboxyphenylboronic acid leads to [Ru(bpy)2(H6)[PF6] while the phosphonic acid analogue is isolated as the zwitterion [Ru(bpy)2(H5) The cyclometallated complexes have been characterized by mass spectrometry, multinuclear NMR spectroscopy, absorption spectroscopy and electrochemistry. [Ru(bpy)2(5) adsorbs onto NiO FTO/NiO electrodes (confirmed by solid state absorption spectroscopy) and its performance in p type dye sensitized solar cells (DSCs) has been compared to that of the standard dye P1; two screen printed layers of NiO give better DSC performances than one layer. Duplicate DSCs containing [Ru(bpy)2(H5) achieve short circuit current densities (JSC) of 3.38 and 3.34 mA cm 2 and photoconversion efficiencies (e) of 0.116 and 0.109% respectively, compared to values of JSC 1.84 and 1.96 mA cm 2 and e 0.057 and 0.051% for P1. Despite its simple dye structure, the performance of [Ru(bpy)2(H5) parallels the best performing cyclometallated ruthenium(II) dye in p type DSCs reported previously (He et al. J. Phys. Chem. C, 2014, 118, 16518) and confirms the effectiveness of a phosphonic acid anchor in the dye and the attachment of the anchoring unit to the pyridine (rather than phenyl) ring of the cyclometallating ligand.
author_names: Fabian Brunner

Nathalie Marinakis

Cederic Wobill

Markus Willgert

Cathrin D Ertl

Tatjana Kosmalski

Markus Neuburger

Biljana Bozic-Weber

Thilo Glatzel

Edwin C Constable

Catherine E Housecroft
title: Modular synthesis of simple cycloruthenated complexes with state of the art performance in p type DSCs
year: 2016

abstract: Abstract For the first time laser assisted sealing using lead free glass frit was successfully applied for producing a DSC panel with a total sealed area of 1638 cm2 and active area of 990 cm2. The panel comprises 90 DSCs individual glass sealed cells (140 mm x 13 mm) arranged in 10 sub modules (150 mm x 150 mm) Indoor aging of individual sub modules in dark and at ambient temperature for 100 days showed rather small decrease of the photocurrent conversion efficiency: 1.23 10 4 day 1. The DSC panel was tested under outdoor working conditions during 47 days in summer time (Porto, Portugal) where the average day illumination level was about 6 kW h m 2. After 47 days of continuous power production the assembled panel kept 86% of the initial efficiency. No leakage of electrolyte or visual defects in the sealed glass frit were detected. Glass sealed DSCs performed superior stability under 1000 h of ageing in a climatic chamber when compared to polymer sealed cells. The results show that the laser assisted sealing can be applied to large area DSC modules.
author_names: Dzmitry Ivanou

R Santos

Jose Macaira

Luisa Andrade

Adelio Mendes
title: Laser assisted glass frit sealing for production large area DSCs panels
year: 2016

abstract: Abstract Chemistry is facing the challenge of delivering new materials for energy harvesting and management. The development of a materials chemistry in which scarce elements are replaced by more abundant and sustainable materials is crucial to the commercial and societal acceptance of these new technologies. This review surveys the use of complexes of Earth abundant metals from the first row of the d block as photosensitizers in dye sensitized solar cells (DSCs) an emerging technology for solar light harvesting in which state of the art devices currently use ruthenium or other platinum group metal complexes as photosensitizers.
author_names: Biljana Bozic-Weber

Edwin C Constable

Catherine E Housecroft
title: Light harvesting with Earth abundant d block metals: Development of sensitizers in dye sensitized solar cells (DSCs)
year: 2013

abstract: Dental stem cells (DSCs) are a promising source of mesenchymal stem cells for use in cell therapy and regenerative medicine. To date, seven types of DSCs have been described in the literature: Dental Pulp Stem Cells (DPSCs) Stem cells from Human Exfoliated Deciduous teeth (SHED) Periodontal Ligament Stem Cells (PDLSCs) Dental Follicle Progenitor Cells (DFPCs) Stem Cells from Apical Papilla (SCAP) Gingival Mesenchymal Stem Cells (GMSCs) and human Natal Dental Pulp Stem Cells (NDP SCs) All these easily accessible stem cells can be derived from dental tissues obtained from young or adult patients.
author_names: Chiara Gardin

Sara Ricci

Letizia Ferroni
title: Dental Stem Cells (DSCs) Classification and Properties
year: 2016

abstract: The adsorption behavior of two symmetrical indolenine based squaraines, indicated with VG1 C2 and VG1 C10, sensitizing electrodeposited mesoporous zinc oxide (ZnO) was studied and compared with that of di tetrabutylammonium cis bis(isothiocyanato) bis(2,2' bipyridyl 4,4' dicarboxylato) ruthenium (II) (N719) The choice of squaraines as metal free dye sensitizers was motivated by their far red NIR sensitivity with respect to the traditional Ru complex based dyes, the ease of their preparation and their higher molar extinction coefficient. The electrochemically grown ZnO here described were porous due to the high volume yield of electrodeposition (about 104 cm3 of ZnO per unit charge of electrolysis) In the present analysis the process of sensitization of TiO2 with the same set of dyes and the performance of the corresponding DSCs were also considered for sake of comparison. VG1 C2 sensitizer proved to be particularly effective electron injector in ZnO electrodes giving larger photocurrents in VG1 C2 sensitized ZnO with respect to TiO2. The latter system presented higher kinetic stability of the photoinjected charges as evidenced by the larger photovoltages of TiO2 based DSCs with respect to ZnO based devices with the same sensitizer. The long alkyl substituents in squaraine VG1 C10 inhibit electron injection in ZnO and a specific effect of electrical passivation of the ZnO surface introduced by the bulky apolar groups was claimed. Overall efficiencies in the order of 1% were measured with the ZnO based DSCs under AM 1.5 solar simulator when the photoactive area and the thickness of ZnO films were 0.5 cm2 and 2 mm, respectively. These results on ZnO based DSCs with the oxide prepared at temperatures below 260 degC are particularly interesting considering the relatively large area and small thickness of the related electrodes, which makes them in principle useful for application in weakly absorbing devices utilizing flexible substrates.
author_names: Iole Venditti

Nadia Barbero

Maria Vittoria Russo

Aldo Di Carlo

Franco Decker

Ilaria Fratoddi

Claudia Barolo

Danilo Dini
title: Electrodeposited ZnO with squaraine sentisizers as photoactive anode of DSCs
year: 2014

abstract: Undyed mesoporous NiO in the configuration of thin film (thickness 2 3 mm) presents photoelectrochemical activity as cathode of a p type dye sensitized solar cell (p DSC) towards the reduction of triiodide to iodide under irradiation with a solar simulator. The photoelectroactivity of the oxide prepared via microwave plasma sintering (or rapid discharge sintering, RDS) has been observed in the spectral range 300 500 nm with the incident photon to current conversion efficiency (IPCE) reaching a maximum of 8.7 at 375 nm. Upon sensitization, the characteristic photoelectrochemical activity of NiO can be either enhanced or depressed depending on the nature of the dye sensitizer. The comparative analysis of the JV and IPCE curves of the p DSCs based on bare NiO and four differently sensitized NiO cathodes reveals that N719, black dye (BD) and commercial squaraine 2 (SQ2) decrease the efficiency of conversion of dyed NiO with respect to bare NiO in the range of photoelectroactivity of the latter (300 500 nm) The fourth dye P1 represents the sole exception since its employment brings about an enhancement of the quantum efficiency of P1 sensitized vs. unsensitized NiO up to a maximum of 21 within the spectral interval of reference for NiO (300 500 nm) Outside the range of NiO photoelectrochemical activity, i.e. l 500 nm, only N719 does not introduce a gain of quantum efficiency with respect to bare NiO despite the observation of spectral sensitization up to 580 nm for N719 sensitized NiO. The impedance spectra recorded under illumination shows a direct proportionality between the overall efficiency (e) of the variously sensitized p DSCs and the amplitude of the semicircle which is generally associated with the process of charge recombination at the electrode/electrolyte interface with e decreasing with the increase of the recombination resistance.
author_names: S Sheehan

Gaia Clara Mercedes Naponiello

Fabrice Odobel

Denis P Dowling

Aldo Di Carlo

Danilo Dini
title: Comparison of the photoelectrochemical properties of RDS NiO thin films for p type DSCs with different organic and organometallic dye sensitizers and evidence of a direct correlation between cell efficiency and charge recombination
venue: Journal of Solid State Electrochemistry
year: 2014