Towards flexibility: metal free plastic cathodes for dye sensitized solar cells

Ahmad, Shahzada,Dell'Orto, Elisa,Yum, Jun-Ho,Kessler, Florian,Nazeeruddin, Mohammad K.,Grä,tzel, Michael The Royal Society of Chemistry 2012 Chemical communications Vol.48 No.78

<P>We report herein lightweight, and economical dye-sensitized solar cells fabrication facilitated by an all plastic, metal free cathode consisting of poly(3,4-ethylenedioxythiophene).</P> <P>Graphic Abstract</P><P>Cost effective, unprecedented solar light harvesting conversion efficiency was achieved with the use of metal free plastic cathodes in DSSCs. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cc35038f'> </P>

A new generation of platinum and iodine free efficient dye-sensitized solar cells

Ahmad, Shahzada,Bessho, Takeru,Kessler, Florian,Baranoff, Etienne,Frey, Julien,Yi, Chenyi,Grä,tzel, Michael,Nazeeruddin, Mohammad K. The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.30

<P>We report a series of cobalt complexes with various polypyridyl ligands, where the oxidation potential is tuned from 0.17 to 0.34 V <I>vs.</I> ferrocene. The highest occupied molecular orbitals (HOMO) of the cobalt complexes were stabilized by adding electron acceptor groups on pyridyl or replacing pyridyl by pyrazole. These complexes are then used as one-electron redox mediators in dye sensitized solar cells (DSSCs) together with polymer based cathode resulting in an excellent performance. The performance of DSSCs using the molecularly engineered cobalt redox shuttle and poly(3,4-alkylthiophenes) based cathode is better than the triiodide/iodide redox shuttle with platinized cathode. The use of high surface area poly(3,4-propylenedioxythiophene) based nanoporous layers allows higher catalytic activity thus minimizing the electrode–electrolyte interface issues.</P> <P>Graphic Abstract</P><P>Molecularly engineered cobalt redox shuttles with tunable oxidation potential, when employed with polymer cathode are new work horse for DSSCs. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp41611e'> </P>

Effect of nano -Al2O3 addition on ion dynamics in polymer electrolytes

Shahzada Ahmad,S.A. Agnihotry 한국물리학회 2009 Current Applied Physics Vol.9 No.1

Polymer electrolytes, which hold the key of successful operation of all solid state ionic devices, have been investigated. An amorphous polymer was used to facsimile fast ion transport in the gel polymer electrolytes (GPE) and room temperature conductivity >10-3 S/cm can be attained. Further, these electrolytes were transformed into composites by dispersing inorganic particles of -Al2O3 (11 nm in size) in varying wt.%. An enhancement in the conductivity for an optimum concentration using LiClO4 as a salt can be obtained and is described in terms of free charge carrier concentration, while the other family of Lithium salts viz. LiTf, LiIm, LiBETI decreases the conductivity marginally. FTIR spectroscopy supports the observed decrease in terms of more association between fillers and salts. It has been realized that the mechanical integrity of these composites increases manifold, without affecting the conductivity, significantly. Polymer electrolytes, which hold the key of successful operation of all solid state ionic devices, have been investigated. An amorphous polymer was used to facsimile fast ion transport in the gel polymer electrolytes (GPE) and room temperature conductivity >10-3 S/cm can be attained. Further, these electrolytes were transformed into composites by dispersing inorganic particles of -Al2O3 (11 nm in size) in varying wt.%. An enhancement in the conductivity for an optimum concentration using LiClO4 as a salt can be obtained and is described in terms of free charge carrier concentration, while the other family of Lithium salts viz. LiTf, LiIm, LiBETI decreases the conductivity marginally. FTIR spectroscopy supports the observed decrease in terms of more association between fillers and salts. It has been realized that the mechanical integrity of these composites increases manifold, without affecting the conductivity, significantly.

Influence of the counter electrode on the photovoltaic performance of dye-sensitized solar cells using a disulfide/thiolate redox electrolyte

Burschka, Julian,Brault, Vincent,Ahmad, Shahzada,Breau, Livain,Nazeeruddin, Mohammad K.,Marsan, Benoî,t,Zakeeruddin, Shaik M.,Grä,tzel, Michael The Royal Society of Chemistry 2012 ENERGY AND ENVIRONMENTAL SCIENCE Vol.5 No.3

<P>Strong scientific interests focus on the investigation of iodine-free redox couples for their application in dye-sensitized solar cells (DSCs). Recently, a disulfide/thiolate-based redox electrolyte has been proposed as a valuable alternative to the conventional I<SUB>3</SUB><SUP>−</SUP>/I<SUP>−</SUP> system due to its transparent and non-corrosive nature. In the work presented herein, we systematically studied the influence of different counter electrode materials on the photovoltaic performance of DSCs employing this promising organic redox electrolyte. Our investigations focused on understanding the importance of electrocatalytic activity and surface area of the electroactive material on the counter electrode, comparing the conventional platinum to cobalt sulfide (CoS) and poly(3,4-ethylenedioxythiophene) (PEDOT). Electrochemical Impedance Spectroscopy has been used to study in detail the interfacial charge transfer reaction at the counter electrode. By using a high surface area PEDOT-based counter electrode, we finally achieved an unprecedented power conversion efficiency of 7.9% under simulated AM1.5G solar irradiation (100 mW cm<SUP>−2</SUP>) which, to the best of our knowledge, represents the highest efficiency that has so far been reported for an organic redox couple.</P> <P>Graphic Abstract</P><P>Investigation of platinum-free electrocatalysts for disulfide-to-thiolate reduction in dye-sensitized solar cells leading to a new record efficiency of 7.9%. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2ee03005e'> </P>

Reinforcement of Electromagnetic Wave Absorption Characteristics in PVDF‑PMMA Nanocomposite by Intercalation of Carbon Nanofibers

Anam Naseer,Muhammad Mumtaz,Muhammad Raffi,Izhar Ahmad,Sabih D. Khan,Rana I. Shakoor,Shaista Shahzada 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.2

With the recent developments in the millimeter and sub-millimeter wave instruments and devices, there is a need to developelectromagnetic (EM) wave absorbing materials in these frequency bands for applications like electromagnetic interferencecontrol, electromagnetic compatibility, etc. In this work, carbon nanofi bers (CNF) were uniformly dispersed in a blend ofpoly(methyl methacrylate), polyvinylidene fl uoride and cyanoacrylate for air spray coating a fi lm on the cellulosic substrates. The samples were characterized for evaluation of their structure, morphology, electrical and EM absorption properties in0.15–1.2 THz range by X-ray diff raction, fi eld emission electron microscopy, I–V measurements and terahertz time domainspectroscopy. These coatings can conveniently be applied to the material surfaces by conventional air spray painting method,which makes this technique cost-eff ective as well as easy to deploy in various applications. The electrical conductivityenhancement in the samples has been attributed to the formation of conducting network by uniform distribution of CNFs inthe insulating polymer matrix. As a result, the shielding eff ectiveness (SE) has been observed to improve with the increasein CNF’s loading in the polymer matrix. The SE is also a function of frequency, which is attributed to the increase in theskin depth. A SE of 20 dB has been estimated in these samples for the frequencies 1 THz and higher, which is of signifi cantimportance for the use of this technique in practical applications.

Microalgal and cyanobacterial strains used for the bio sorption of copper ions from soil and wastewater and their relative study

Shah Zada,Saleem Raza,Sikandar Khan,Arshad Iqbal,Zhang Kai,Aftab Ahmad,Midrar Ullah,Mohib Kakar,Pengcheng Fu,Haifeng Dong,Zhang Xueji 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.105 No.-

Heavy metals and other organic pollutants are the hazardous materials causing soil and water pollution,hence, bioremediation of these components is a matter of concern for environmental biotechnologists. Twenty one microalgal and cyanobacterial strains were evaluated for removal of copper from aqueoussolutions and soil containing 10 ppm copper. 5 out of 21 strains have shown comparatively higher toleranceto copper stress. The biosorption capabilities of all the five strains were assessed using techniqueslike ultraviolet (UV) spectrophotometers, scanning electron microscope (SEM), inductively coupledplasma mass spectrometry (ICP-MS), and confocal Microscopy. It was found that the five selected strainscould grow normally upon incubating with 20 ppm of Cu. Copper removal efficiencies of these microalgae(S. obliquus, A. braunii, C. fusca, L. JSC-1 and C. saccharophila in water were 99.9, 99.3, 97, 96.7, and 96%,while for soil was 73, 75, 71, 70, 68%, respectively. A minor leakage of nucleic acid and protein weredetected with time. Furthermore, no any visible morphological changes were observed after six daysof treatment, while minor changes were noticed after 12 days in water, and severe morphological deformationsoccurred after 24 days of bioremediation in soil. Our findings reveal that the selected microalgalstrains have high potential for Cu bioremediation at certain concentration for 12 days exposure fromwater and 24 from soil.