Search

Over the past three decades, dye‐sensitized solar cells (i. e. Grätzel cells) have evolved from a pioneering concept of molecular photovoltaics to large‐scale industrial deployment. In this review article, we provide a historical overview of the developments with a focus on the scientific advancements that have set the stage for this technology to emerge and thrive. This involves insights into the (photo)electrochemistry of the underlying processes, molecular engineering of dyes, redox shuttles, and hole‐transporting materials, as well as their implementation into solar cells. We further outline applications and future perspectives, involving the long‐lasting objective to develop efficient solid‐state alternatives to conventional dye‐sensitized solar cells. [ABSTRACT FROM AUTHOR]

Dye‐sensitized solar cells (DSCs) based on copper(II/I) redox mediators have recently achieved notable performance progress through tailoring the ligand structure of the copper complexes, exploiting cosensitization, and introducing an advanced device structure. In order to further improve the power conversion efficiency (PCE), it is imperative to develop wide spectral‐response photosensitizers compatible with the copper(II/I) redox mediators while attaining a high Voc. Herein, a blue photosensitizer coded R7 is reported, which is purposely designed for highly efficient DSCs with copper‐based electrolytes. R7 features a strong electron‐donating segment of 9,19‐dihydrobenzo[1′,10′ ]phenanthro[3′,4′:4,5]thieno[3,2‐b]benzo[1,10]phenanthro[3,4‐d]thiophene conjugated with a bulky auxiliary donor N‐(2,4′‐bis(hexyloxy)‐[1,1′‐biphenyl]‐4‐yl)‐2,4′‐bis(hexyloxy)‐N‐methyl‐[1,1′‐biphenyl]‐4‐amine and the electron acceptor 4‐(7‐ethynylbenzo[c][1,2,5]thiadiazol‐4‐yl)benzoic acid. The blue dye R7 with bulkier auxiliary donor moiety in the DSC largely outperforms the reference dye R6, which has a smaller bis(4‐(hexyloxy)phenyl)amine donor unit. Transient absorption spectroscopy and electrochemical impedance spectroscopy measurements show that the R7 based DSC has a higher charge separation yield, a higher charge collection efficiency, and lower charge recombination with the copper electrolyte than the R6 based counterpart. A cosensitized system of R7 and Y123 for the DSC presents an outstanding PCE of 12.7% and retains 90% of its initial value after 1000 h of light soaking under 1 sun at 45 °C. [ABSTRACT FROM AUTHOR]

Dye‐sensitized solar cells (DSSCs) based on CuII/I bipyridyl or phenanthroline complexes as redox shuttles have achieved very high open‐circuit voltages (VOC, more than 1 V). However, their short‐circuit photocurrent density (JSC) has remained modest. Increasing the JSC is expected to extend the spectral response of sensitizers to the red or NIR region while maintaining efficient electron injection in the mesoscopic TiO2 film and fast regeneration by the CuI complex. Herein, we report two new D‐A‐π‐A‐featured sensitizers termed HY63 and HY64, which employ benzothiadiazole (BT) or phenanthrene‐fused‐quinoxaline (PFQ), respectively, as the auxiliary electron‐withdrawing acceptor moiety. Despite their very similar energy levels and absorption onsets, HY64‐based DSSCs outperform their HY63 counterparts, achieving a power conversion efficiency (PCE) of 12.5 %. PFQ is superior to BT in reducing charge recombination resulting in the near‐quantitative collection of photogenerated charge carriers. [ABSTRACT FROM AUTHOR]

The excited‐state evolution property of organic sensitizers plays a vital role in the interfacial exciton dissociation yield and ultimate power output of an organic dye‐sensitized solar cell. In this paper, we select two 2H‐dinaphthopentacene‐based organic donor–acceptor dyes as well as their composition segments and scrutinize the evolution of the excited‐state dynamics of organic materials from the 2H‐dinaphthopentacene core to its derivatives by sequentially tethering an auxiliary donor diarylamine, and an electron acceptor, 4‐(7‐ethynylbenzo[c][1,2,5]thiadiazol‐4‐yl)benzoic acid. Time‐resolved spectroscopy measurements and density functional theory calculations show that the degree of intramolecular photoinduced charge transfer plays a crucial role in determining the lifetime of the equilibrium excited‐state. Moreover, both the 2H‐dinaphthopentacene chromophore core and its derivatives have an obvious dynamic Stokes shift in toluene, which is also observed for ultimate dyes grafted on oxide films, indicating the occurrence of a large energy relaxation from the optically generated hot excited‐state to the equilibrium excited‐state. This large energy loss leads to a broad time scale for electron injection, which should be carefully manipulated for future dye and device development. [ABSTRACT FROM AUTHOR]

Continuous studies on the use of a polycyclic aromatic hydrocarbon as the central block of an organic photosensitizer have brought forth a new opportunity toward efficiency enhancement of dye‐sensitized solar cells (DSCs). In this paper, a nonacyclic aromatic hydrocarbon 9,19‐dihydrodinaphtho[3,2,1‐de:3′,2′,1′‐op]pentacene, tethered with four 4‐hexylphenyl solubilizing groups is reported. The novel chromophore 9,9‐19‐19‐tetrakis(4‐hexylphenyl)‐9,19‐dihydrodinaphtho[3,2,1‐de:3′,2′,1′‐op]pentacene is further functionalized with diarylamines and 4‐(7‐ethynylbenzo[c][1,2,5]thiadiazol‐4‐yl)benzoic acid to produce two donor–acceptor (D–A) organic photosensitizers, achieving good power conversion efficiencies up to 10.2% in DSCs. [ABSTRACT FROM AUTHOR]

Most photovoltaic (PV) technologies are opaque to maximize visible light absorption. However, see-through solar cells open additional perspectives for PV integration. Looking beyond maximizing visible light harvesting, this work considers the human eye photopic response to optimize a selective near-infrared sensitizer based on a polymethine cyanine structure (VG20-C x ) to render dye-sensitized solar cells (DSSCs) fully transparent and colorless. This peculiarity was achieved by conferring to the dye the ability to strongly and sharply absorb beyond 800 nm (S 0 -S 1 transition) while rejecting the upper S 0 -S n contributions far in the blue where the human retina is poorly sensitive. When associated with an aggregation-free anatase TiO 2 photoanode, the selective NIR-DSSC can display 3.1% power conversion efficiency, up to 76% average visible transmittance (AVT), a value approaching the 78% AVT value of a standard double glazing window while reaching a color rendering index (CRI) of 92.1%. The ultrafast and fast charge transfer processes are herein discussed, clarifying the different relaxation channels from the dye monomer excited states and highlighting the limiting steps to provide future directions to enhance the performances of this nonintrusive NIR-DSSC technology., Competing Interests: The authors declare no competing financial interest., (© 2021 American Chemical Society.)

We report a blue dye, coded as R6, which features a polycyclic aromatic hydrocarbon, 9,19-dihydrobenzo[1',10']phenanthro[3',4':4,5]thieno[3,2-b]benzo[1,10]phenanthro[3,4-d]thiophene, coupled with a diarylamine electron donor and 4-(7-ethynylbenzo[c][1,2,5]thiadiazol-4-yl)benzoic acid acceptor. Dye R6 displays a brilliant sapphire color in a sensitized TiO 2 mesoporous film with a Co(II/III) tris(bipyridyl)-based redox electrolyte. The R6 based dye-sensitized solar cell achieves an impressive power conversion efficiency of 12.6% under standard air mass 1.5 global, 100 mW cm -2 , and shows a remarkable photostability.

Three new tris-heteroleptic complexes of ruthenium(II) were designed by coordinating the metal center with cyclometalating, anchoring, and auxiliary ligands with different donor substituents. N-Hexylcarbazole, N-hexylphenothiazine, and N-hexyldiphenylamine donor moieties were used as substituents on the auxiliary ligands for SA633, SA634, and SA635, respectively. Complexes were characterized by 1 H and 13 C 2D-COSY NMR techniques. These complexes provide power conversion efficiencies in the range of 7.6-8.2% when they are employed in state of the art dye-sensitized solar cells (DSCs) with cobalt electrolyte. Various electrochemical and transient techniques were used to unveil the unexpected differences in the performance of these very similar sensitizers.

We synthesize two new metal-free donor-acceptor organic dyes (C266 and C267) featuring a N-annulated perylene block. Owing to the improved coplanarity of conjugated units as well as the prolonged conjugation upon inserting a triple bond between the triarylamine and perylene segments, the C267 dye exhibits a slightly red-shifted absorption peak and an enhanced maximum molar absorption coefficient with respect to its reference dye C266, leading to an improved photocurrent output in dye-sensitized solar cells. However, the triple-bond introduction also brings forth an over 100 mV reduced open-circuit photovoltage owing to faster interfacial charge recombination, which presents a clear correlation with a reduced mean thickness of self-assembled dye layer on titania as revealed by X-ray reflectivity measurements. The C266 dye, albeit with a relatively weaker light-harvesting capacity, displays a higher power conversion efficiency of 9.0% under the 100 mW cm(-2), simulated AM1.5G sunlight.

In this article, TiO(2)-Carbon-rGO (GCT) three-component composite material has been constructed by anchoring TiO(2) nanoparticles (NPs) encapsulated in carbon shells onto reduced graphene oxide (rGO) sheets. The structure of GCT was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), N(2) adsorption-desorption isotherms, and transmission electron microscopy (TEM). This material shows a superior retention as the anode materials in lithium ion battery with a specific discharge capacity of 188 mA h g(-1) in the initial cycle and 158 mA h g(-1) after 100 cycles.