Push-pull zinc phthalocyanine bearing hexa-tertiary substituted carbazolyl donor groups for dye-sensitized solar cells

An asymmetrical, push-pull phthalocyanine bearing bulky tert-butylcarbazolyl moieties as electron donor and carboxylic acid as anchoring group was synthetized and tested as a photosensitizer in dye-sensitized solar cells (DSSC). The new photosensitizer was characterized by 1H and 13C NMR, UV-Vis and mass spectrometry. The bulky tert-butylcarbazolyl moieties avoid the aggregation of the phthalocyanine dye. DFT studies indicate that the HOMO is delocalized throughout the π-electron system of the substituted phthalocyanine and the LUMO is located on the core of the molecule with a sizable electron density distribution on carboxyl groups. The new dye has been used as a photosensitizer in transparent and opaque dye-sensitized solar cells, which exhibit poor efficiencies related to a low JscThis work was financially supported by the Kuwait Foundation for the Advancement of Science (Grant Number PN18-12-SC01) and the RSP unit general facilities of the Faculty of Science GFS (GS 01/01, GS 03/01, GS 01/03, GS 01/05, and GS 02/13) (S.M.). T.T. thanks MINECO (project CTQ2017-85393-P) and ERA-NET/European Commission/MINECO, (UNIQUE, SOLAR-ERA.NET Cofund 2 Nº 008/PCI2019-111889-2). R.D. acknowledges ANR for funding through ODYCE project. (Grant agreement No ANR-14-OHRI-0003-01). RD thanks European Research Council (ERC) for funding. This project has received funding from the European Union’s Horizon 2020 research and innovation program (grant agreement No 832606)—Project PISC

Visible and near-infrared organic photosensitizers comprising isoindigo derivatives as chromophores: synthesis, optoelectronic properties and factors limiting their efficiency in dye solar cells

The development of ruthenium-free organic photosensitizers showing panchromatic absorption up to the near-infrared (NIR) region for application in dye-sensitized solar cells (DSSCs) is still scarce. Among the sensitizers with absorption beyond 700 nm and developed for DSSCs, only zinc-phthalocyanine and boron-dibenzopyrromethene-based dyes have been able to reach efficiencies as high as 6%. Here we report metal-free organic dyes based on isoindigo, thieno-isoindigo or benzo-thieno-isoindigo chromophores that absorb in the UV-visible and NIR spectral range up to 900 nm. These molecules, that exhibit purple, blue, or green hues, were used to sensitize TiO2 mesoporous electrodes in order to fabricate DSSCs with an iodide/triiodide-based electrolyte. Advanced photophysical characterizations, including charge extraction, transient photovoltage, and laser transient absorption spectroscopy experiments, combined with density functional theory modeling and computational investigations allow us to fully unravel the interfacial processes at the origin of the solar cell performances and to identify the limiting factors. A power conversion efficiency as high as 7% associated with a Jsc close to 19 mA cm−2 was obtained with one of the dyes, which is comparable to those of the best panchromatic organic dyes reported so far. We also demonstrate in this work that the Voc of the solar cells is linearly correlated to the dipolar moments of the oxidized dyes, the molecules possessing larger dipoles leading to the highest Voc value

Characterization of Photochromic Dye Solar Cells Using Small-Signal Perturbation Techniques

Photochromic dye-sensitized solar cells (DSSCs) are novel semi-transparent photovoltaic devices that self-adjust their optical properties to the irradiation conditions, a feature that makes them especially suitable for building integrated photovoltaics. These novel solar cells have already achieved efficiencies above 4%, and there are multiple pathways to improve the performance. In this work, we conduct a full characterization of DSSCs with the photochromic dye NPI, combining electrical impedance spectroscopy (EIS) and intensity-modulated photocurrent spectroscopy (IMPS). We argue that the inherent properties of the photochromic dye, which result in a modification of the functioning of the solar cell by the optical excitation that also acts as a probe, pose unique challenges to the interpretation of the results using conventional models. Absorption of light in the visible range significantly increases when the NPI dye is in the activated state; however, the recombination rate also increases, thus limiting the efficiency. We identify and quantify the mechanism of enhanced recombination when the photochromic dye is activated using a combination of EIS and IMPS. From the comparison to a state-of-the-art reference dye (RK1), we were able to detect a new feature in the IMPS spectrum that is associated with the optical activation of the photochromic dye, providing a useful tool for assessing the electronic behavior of the device under different conditions of light excitation. This study provides guidelines to adequate characterization protocols of photochromic solar cells and essential insights on the interfacial electronic processes.Universidad Pablo de Olavide / CEA Grenobl

Influence of Redox Couple on the Performance of ZnO Dye Solar Cells and Minimodules with Benzothiadiazole-Based Photosensitizers

ZnO-based dye-sensitized solar cells exhibit lower efficiencies than TiO2-based systems despite advantageous charge transport dynamics and versatility in terms of synthesis methods, which can be primarily ascribed to compatibility issues of ZnO with the dyes and the redox couples originally optimized for TiO2. We evaluate the performance of solar cells based on ZnO nanomaterial prepared by microwave-assisted solvothermal syn- thesis, using three fully organic benzothiadiazole-based dyes YKP- 88, YKP-137, and MG-207, and alternative electrolyte solutions with the I−/I3−, Co(bpy)32+/3+, and Cu(dmp)21+/2+ redox couples. The best cell performance is achieved for the dye−redox couple combination YKP-88 and Co(bpy)32+/3+, reaching an average −− efficiency of 4.7% and 5.0% for the best cell, compared to 3.7% and 3.9% for the I /I3 couple with the same dye. Electrical impedance spectroscopy highlights the influence of dye and redox couple chemistry on the balance of recombination and regeneration kinetics. Combined with the effects of the interaction of the redox couple with the ZnO surface, these aspects are shown to determine the solar cell performance. Minimodules based on the best systems in both parallel and series configurations reach 1.5% efficiency for an area of 23.8 cm2.Área de Química Físic

Chem. Sci. (2023) : Push-pull photochromic dyes for semi-transparent solar cells with light-adjustable optical properties and high color-rendering index

Raw data for the article of Fauvel et al. Chem. Sci. 2023, DOI: 10.1039/d3sc02328

Des cellules solaires dont la transparence et la production d’énergie s’adaptent aux conditions d’ensoleillement

En laboratoire, les cellules solaires à colorant démontrent aujourd’hui des efficacités supérieures à 14% et peuvent être semi-transparentes, colorées et très efficaces sous de faibles irradiations. Elles ont récemment amorcé leur développement industriel avec des exemples d’intégration dans des façades de bâtiments. Dans cet article, nous rappellerons le principe de fonctionnement de ces cellules, puis nous reviendrons sur nos travaux visant à développer des colorants applicables en cellules semitransparentes. Enfin, nous présenterons une nouvelle classe de photosensibilisateurs qui permettent d’obtenir des cellules solaires capables de changer de couleur et d’auto-ajuster simultanément leur transparence et leur production d’énergie en fonction des conditions d’ensoleillement

Editors’ choice collection on organic photovoltaics: back in the game

International audienceAssociate Editors Yana Vaynzof and Renaud Demadrille highlight recent research in organic photovoltaics in this themed collection (rsc.li/OrganicPhotovoltaics)

Nouvelles Cellules Solaires Hybrides contenant des Oxydes Sensibilisés par des Colorants Organiques

Forum Nanorgasol " Rencontres Photovoltaïques Organiques et Hybrides

Implementation of data-cube pump–probe KPFM on organic solar cells

International audienceAn implementation of pump-probe Kelvin probe force microscopy (pp-KPFM) is reported that enables recording the time-resolved surface potential in single-point mode or over a 2D grid. The spectroscopic data are acquired in open z-loop configuration, which simplifies the pp-KPFM operation. The validity of the implementation is probed by measurements using electrical pumping. The dynamical photoresponse of a bulk heterojunction solar cell based on PTB7 and PC71BM is subsequently investigated by recording point-spectroscopy curves as a function of the optical power at the cathode and by mapping 2D time-resolved images of the surface photovoltage of the bare organic active layer