Charge photogeneration and transport in AgBis2 nanocrystal films for photovoltaics

Solution-processed AgBiS2 nanocrystal films are a promising material for nontoxic, earth-abundant solar cells. While solar cells with good device efficiency are demonstrated, so far, hardly anything is known about charge generation, transport, and recombination processes in these films. Here, a photoinduced time-resolved microwave conductivity study on AgBiS2 nanocrystal films is presented. By modeling the experimental data with density-dependent recombination processes, the product of the temperature-dependent electron and hole quantum yield and mobility, and the electron and hole recombination kinetics are determined

Electrical effects of metal nanoparticles embedded in ultra-thin colloidal quantum dot films

Plasmonic light trapping can increase the absorption of light in thin semiconductor films. We investigate the effect of embedded metal nanoparticle (MNP) arrays on the electrical characteristics of ultra-thin PbS colloidal quantum dot (CQD) photoconductors. We demonstrate that direct contact with the metalnanoparticles can suppress or enhance the photocurrent depending on the work function of the metal, which dominates the optical effects of the particles for ultra-thin films. These results have implications for designing plasmonic CQD optoelectronic devices.This research has been supported by Fundacio0 Privada Cellex Barcelona and the European Commission’s Seventh Framework Programme for Research under contract PIRG06-GA-2009-256355 and the Ministerio de Ciencia e Innovacion under Contract No. TEC2011-24744

High frequency response of adenine-derived carbon in aqueous electrochemical capacitor

Electrochemical capacitors are attractive power sources, especially when they are able to operate at high frequency (high current regime). In order to meet this requirement their constituents should be made of high conductivity materials with a suitable porosity. In this study, enhanced power and simultaneously high capacitance (120 F g−1 at 1 Hz or 10 A g−1) electrode material obtained from carbonized adenine precursor is presented. A micro/mesoporous character of the carbon with optimal pore size ratio and high surface area was proven by the physicochemical characterization. The beneficial pore structure and morphology resembling highly conductive carbon black, together with a significant nitrogen content (5.5%) allow for high frequency response of aqueous capacitor to be obtained. The carbon/carbon symmetric capacitor (in 1 mol L−1 Li2SO4) has been tested to the voltage of 1.5 V. The cyclic voltammetry indicates a good electrochemical response even at high scan rate (50 mV s−1). The cyclability of the capacitor is comparable to the one operating with commercial carbon (YP50F). The adenine-based capacitor is especially favourable for stationary applications requiring high power.Partners acknowledge M-ERA.NET network, MCIN/AEI/10.13039/501100011033 (Ref. PCI2019–103637), CIBER-BBN, ICTS ‘‘NANBIOSIS’’, ICTS ELECMI node "Laboratorio de Microscopias Avanzadas", National Science Centre, Poland (2018/30/Z/ST4/00901), and Ministrstvo za izobraževanje, znanost in šport for financial support and the grant of Ministry of Science and Higher Education in Poland, no. 0911/SBAD/2101. A.V., B.T., E.T. and R.D. additionally acknowledge financial support from the Slovenian Research Agency (ARRS) research core funding P2–0393.Peer reviewe

Converting homogeneous to heterogeneous in electrophilic catalysis using monodisperse metal nanoparticles

A continuing goal in catalysis is the transformation of processes from homogeneous to heterogeneous. To this end, nanoparticles represent a new frontier in heterogeneous catalysis, where this conversion is supplemented by the ability to obtain new or divergent reactivity and selectivity. We report a novel method for applying heterogeneous catalysts to known homogeneous catalytic reactions through the design and synthesis of electrophilic platinum nanoparticles. These nanoparticles are selectively oxidized by the hypervalent iodine species PhICl{sub 2}, and catalyze a range of {pi}-bond activation reactions previously only homogeneously catalyzed. Multiple experimental methods are utilized to unambiguously verify the heterogeneity of the catalytic process. The discovery of treatments for nanoparticles that induce the desired homogeneous catalytic activity should lead to the further development of reactions previously inaccessible in heterogeneous catalysis. Furthermore, our size and capping agent study revealed that Pt PAMAM dendrimer-capped nanoparticles demonstrate superior activity and recyclability compared to larger, polymer-capped analogues

Photocatalytic rermoval of contaminants in water using nanostructured metal oxides

Resumen del póster presentado a la XXXVIII Reunión Bienal de la Real Sociedad Española de Química, celebrada en el Palacio de Congresos de Granada, del 27 de junio al 30 de junio de 2022.An important variety of metal oxides are photoactive semiconductor solids with the capacity to generate Reactive Oxygen Species (ROS) in aqueous media. The excellent oxidizing capacity of these ROS has been studied by the scientific community in the elimination of pollutants as part of the Advanced Oxidation Processes (AOPs) in the purification of polluted water. The main photocatalysts used to date (TiO2, ZnO, g-C3N4...) are only capable of being photoactivated with UV radiation, which means that they can only take advantage of a small fraction of the solar spectrum; or require the use of UV lamps, with the consequent energy consumption. For this reason, this work has proposed the development of new photocatalysts with narrower band gaps capable of generating ROS when irradiated with Visible-NIR photons, thus taking advantage of the largest possible portion of the sunlight spectrum. New nanostructured metal oxides based on Fe and W, photoactive with visible light, have been obtained. In addition, some hybrids consisting of photoactive substrates with semiconductor nanocrystals have been developed, thus improving the photocatalytic properties of the initial materials separately. Finally, all these materials have been tested and optimized in photocatalysis experiments in aqueous suspension of model pollutants.Peer reviewe

Resonance energy transfer from PbS colloidal quantum dots to bulk silicon: the road to hybrid photovoltaics

Semiconductor Quantum Dots (QDs) are promising materials for photovoltaic applications because they can be engineered to absorb light from visible to near infrared and single absorbed photons can generate multiple excitons. However, these materials suffer from low carrier mobility, which severely limits the prospects of efficient charge extraction and carrier transport. We take advantage of the optical properties of QDs and overcome their drawback by using a hybrid photovoltaic device. This photovoltaic configuration exploits the absorption of solar photons in the QDs and the transfer of excitons from the QDs to a silicon p-n junction. We study the Resonance Energy Transfer (RET) mechanism to inject excitons from the QDs into the depletion layer of a silicon p-n junction. Lead sulphide (PbS) nanocrystals are deposited onto the silicon substrate and the efficiency of Resonance Energy Transfer (RET) from the PbS nanoparticles to bulk silicon is investigated. We study the efficiency of this transfer channel between the PbS nanocrystals and silicon by varying their separation distance. These results demonstrate RET from colloidal quantum dots to bulk silicon. Temperature measurements are also presented and show that the RET efficiency is as high as 44% at room temperature. Such a hybrid photovoltaic device makes a potentially inexpensive scheme for achieving high-efficiency and low-cost solar-cell platforms

Time-resolved spectroscopic study of resonant energy transfer between lead-sulphide quantum dots and bulk silicon

The brightness, large absorption cross-section and flexibility of colloidal nanocrystal quantum-dots (QDs) make these materials promising candidates for light harvesting applications. The difficulty of efficiently extracting photogenerated carriers from the QDs however drastically limits the power conversion efficiency of NQD solar cells. A possible way to circumvent these issues is to engineer hybrid devices that utilize alternative energy transfer schemes to effectively separate light harvesting and charge extraction in different materials. In this context, hybrid bulk semiconductor/QDs devices coupled through near-field resonant energy transfer offer a promising route towards low cost ultra-thin photovoltaics. In this work, we demonstrate non-radiative resonance energy transfer between lead sulphide (PbS) QDs and bulk silicon using time-resolved spectroscopy

New non-graphitizable carbon/nanocrystals hybrids with enhanced electrochemical properties for Na-ion batteries

Resumen del trabajo presentado a la XXXVIII Reunión Bienal de la Real Sociedad Española de Química, celebrada en el Palacio de Congresos de Granada, del 27 de junio al 30 de junio de 2022.Peer reviewe

Alkynyldiphenylphosphine d8(Pt, Rh, Ir) complexes: contrasting behavior toward cis-[Pt(C6F5)2(THF)2]

The synthesis and reactivity toward cis-[Pt(C6F5)2(THF)2] of several alkynylphosphine d8 complexes, [Pt(C6F5)(PPh2C⋮CPh)3](CF3SO3), 1, [M(COD)(PPh2C⋮CPh)2](ClO4) (M = Rh, 2, and Ir, 3), and [Pt(o-C6H4E2)(PPh2C⋮CPh)2] (E = O, 6, and S, 7), are reported. Whereas 1 gives rise to the diinserted product 8, which evolves in solution to the bis(diphenylphosphine)naphthalene-based mononuclear complex 9, analogous reactions with 2 or 3 give mixtures of products. The reactions with 6 or 7 afford binuclear heterobridged (μ-κE-o-C6H4E2)/(μ-κP:η2-PPh2C⋮CPh) 11 and 12 or trinuclear (μ3-κ2EE‘-o-C6H4E2)/(μ-κP:η2-PPh2C⋮CPh)2 13 and 14 complexes

Synthesis, characterization, and application in rechargeable batteries of CuXS-rGO aerogels

Resumen del trabajo presentado a la XXXVIII Reunión Bienal de la Real Sociedad Española de Química, celebrada en el Palacio de Congresos de Granada, del 27 de junio al 30 de junio de 2022.Authors acknowledge the M-ERA.NET (NOEL) project, PCI2019-103637 funded by MCIN/AEI/10.13039/501100011033.Peer reviewe