IoT-enabled dye-sensitized solar cells: an effective embedded tool for monitoring the outdoor device performance.

Herein, we have developed a tool for monitoring the outdoor performance of dye-sensitized solar cells. In this regard, a new dye consisting of an N-aryl-substituted imidazole with N-alkylated carbazole as the donor and cyanoacrylic acid as the acceptor has been designed. The overall power conversion efficiency of the designed dye reached ∼50%, with respect to that of the N719-based device (4%) under similar experimental conditions. Further, the device was interfaced with an IoT system, which measured the voltage and transmitted the device parameters to the user's mobile phone through a cloud channel. The developed IoT tool provides a resolution of 0.0315 mV and a round-trip delay time of <0.32 s for transmitting the information to the user's mobile phone.

Zn-Porphyrin propped with hydantoin anchor: synthesis, photophysics and electron injection/recombination dynamics.

In this work, Zn-porphyrin with a hydantoin anchor (ZnPHy) was designed and synthesized for dye-sensitized solar cell (DSC) applications. The synthesized ZnPHy was well characterized using IR, NMR and mass spectral techniques, and satisfactory results were obtained. Cyclic voltammetry, UV-visible absorption, steady-state fluorescence, time-resolved fluorescence and transient absorption spectroscopic techniques were employed to elucidate the electrochemical and photophysical properties of ZnPHy. The obtained properties revealed that the synthesized ZnPHy can be used as a photosensitizer for DSC applications. The nature of ZnPHy binding onto the TiO2 surface was investigated using ATR-FTIR and UV-Vis absorption measurements. The amount of adsorbed ZnPHy on TiO2 surface was reasonably fit using the Langmuir adsorption isotherm, with a binding constant value of 1.03 × 105 M-1. Time-resolved measurements were used to elucidate the rate of electron injection and the regeneration and recombination kinetics for ZnPHy/TiO2 film. The ZnPHy showed a high electron injection rate with a ϕinj of 99%. Intriguingly, the rate of electron recombination is much slower than the rates reported for carboxyl-based Zn-porphyrins. Such a high electron injection and slow electron recombination rate are beneficial to produce long-lived electrical current in a photovoltaic device. Thus, the ZnPHy-sensitized TiO2 electrode showed the best photovoltaic performance, with the short-circuit photocurrent density (JSC), open-circuit voltage (VOC) and fill factor (ff) of 3.49 mA cm-2, 0.6 V and 0.52, respectively, yielding an overall conversion efficiency (η) of 1.01%. For comparison, the ZnCOOH-sensitized electrode was also fabricated under the same conditions and yielded the η value of 0.84%. Hence, the hydantoin moiety could be a potential alternative anchoring group for DSC applications.

A combined experimental and computational investigation on pyrene based D-π-A dyes.

The geometry (twist vs. planar) of a dye is one of the most pivotal factors for determining intramolecular charge transfer (ICT), light harvesting and photovoltaic properties of dye-sensitized solar cells. In order to comprehend the role of dye geometry on the above properties, we have devised the pyrene based D-π-A dyes namely 2-cyano-3-(5-pyren-1-yl-furan-2-yl)-acrylic acid (PFCC) and 2-cyano-3-(5-pyren-1-ylethynyl-furan-2-yl)-acrylic acid (PEFCC). The synthesized pyrene dyes were well characterized by NMR and EI-MS spectrometry. In both the dyes, the donor (pyrene) and acceptor (cyanoacrylic acid) segments remained the same. The varied π-spacers were furan and ethynyl furan. The influences of the ethynyl spacer on the energy levels, light absorption, dynamics of excited states and photovoltaic properties of the DSCs were systematically investigated via theoretical calculations and spectroscopic measurements. UV-visible absorption spectral measurements indicated that the introduction of the ethynyl spacer enhances the molar absorptivity of a dye (PEFCC) in the order of 2, but does not shift the absorption range, which is consistent with the results obtained from density functional theory (DFT) calculations. The theoretical analysis indicated that the charge transfer transition is mainly constituted of the HOMO to the LUMO that were found to be located on donor and acceptor segments, respectively, which is supportive for efficient charge separation and electron injection processes. TDDFT calculations highlighted that the LUMO of the PEFCC dye is more stabilized by the incorporation of the ethynyl group between the pyrene and furan moieties that aid to inject electrons efficiently into TiO2 thereby resulting in an enhanced power conversion efficiency of 2.47% when compared to the PFCC dye. Notably, the overall conversion efficiency of the PEFCC dye reached 60% with respect to that of an N719-based device (4.12%) fabricated under similar conditions. Transient absorption kinetic studies demonstrated that a slower charge recombination rate is an essential factor behind enhanced efficiencies in PEFCC based cells.

Using an airbrush pen for layer-by-layer growth of continuous perovskite thin films for hybrid solar cells.

In this manuscript we describe hybrid heterojunction solar cells, having the device architecture glass/indium tin oxide/poly(3,4-ethylenedioxythiopene)/poly(styrenesulfonic acid)/perovskite/[6,6]-phenyl-C61-butyric acid methyl ester/C60/2,9-dimethyl- 4,7-diphenyl-1,10-phenanthroline/Al, fabricated using lead halide perovskite obtained through spray-coating at a low precursor concentration. To study the relationship between the morphology and device performance, we recorded scanning electron microscopy images of perovskite films prepared at various precursor ratios, spray volumes, substrate temperatures, and postspray annealing temperatures. Optimization of the spray conditions ensured uniform film growth and high surface area coverage at low substrate temperatures. Lead halide perovskite solar cells prepared under the optimal conditions displayed an average power conversion efficiency (PCE) of approximately 9.2%, with 85% of such devices having efficiencies of greater than 8.3%. The best-performing device exhibited a short-circuit current density of 17.3 mA cm(-2), a fill factor of 0.63, and an open-circuit voltage of 0.93 V, resulting in a PCE of 10.2%. Because spray-coating technology allows large-area deposition, we also fabricated devices having areas of 60 and 342 mm(2), achieving PCEs with these devices of 6.88 and 4.66%, respectively.

Organic thin film transistors as selective sensing platforms for Hg²âº ions and the amino acid cysteine.

In this short communication we report a sensor for divalent mercuric (Hg²âº) ions that we constructed from a perylene bisimide (PBI)-based organic thin film transistor. We improved the performance of the n-channel device by positioning N,N'-dioctyl-3,4,9,10-perylenedicarboximide between the dielectric and the active layer (PBI), increasing the electron mobility (µ) from 0.002 to 0.25±0.04 cm² V⁻¹ s⁻¹ and enhancing the on/off ratio (I(on)/I(off)) by two orders of magnitude (from 10² to 104). Based on a "thymine-Hg²âº-thymine" mechanism and monitoring the shift in the threshold voltage (V(th)), we used this transistor to discriminate Hg²âº ions from mixed ion solutions and it extended to different concentration Hg²âº solutions (from 50 to 350 µM). By monitoring the shifts in drain current (I(DS)) and V(th), we also used this bilayer device as a sensor for cysteine, a thiol-containing amino acid; the selective detection of cysteine was accompanied by a red shift in the fluorescence maximum of PBI, from 532 to 537 nm.

Synthesis of main-chain metallo-copolymers containing donor and acceptor bis-terpyridyl ligands for photovoltaic applications.

Two random (Zn(II)-based P1-P2) and two alternating (Ru(II)-based P3-P4) metallo-copolymers containing bis-terpyridyl ligands with various central donor (i.e., fluorene or carbazole) and acceptor (i.e., benzothiadiazole) moieties were synthesized. The effects of electron donor-acceptor interactions with metal (Zn(II) and Ru(II)) ions on their thermal, optical, and electrochemical properties were investigated. Because of the strong ICT transitions between donor and acceptor ligands in both Zn(II)- and Ru(II)-based metallo-coplymers and MLCT transitions in Ru(II)-based metallo-coplymers, the absorption spectra covered a broad range of 260-750 nm with the band gaps of 1.57-1.77 eV. In addition, the introduction of Ru(II)-based metallo-coplymer P4 mixed with PC(60)BM as an active layer of the BHJ solar cell device exhibited the highest PCE value up to 0.90%.