The feasibility of using visible/near-infrared (Vis/NIR) spectroscopy was assessed for non-destructive detection of diazinon residues in intact cucumbers. Vis/NIR spectra of diazinon solution and cucumber samples without and with different concentrations of diazinon residue were analysed at the range of 450–1000 nm. Partial least squares-discriminant analysis (PLS-DA) models were developed based on different spectral pre-processing techniques to classify cucumbers with contents of diazinon below and above the MRL as safe and unsafe samples, respectively. The best model was obtained using a first-derivative method with the lowest standard error of cross-validation (SECV = 0.366). Moreover, total percentages of correctly classified samples in calibration and prediction sets were 97.5% and 92.31%, respectively. It was concluded that Vis/NIR spectroscopy could be an appropriate, fast and non-destructive technology for safety control of intact cucumbers by the absence/presence of diazinon residues.

Controlling the phenomenological morphology effects on the performance of the perovskite solar cell (PSC) is a continuing concern due to its photo-physical complexity and the existing contrary reports. Distinguishing the effect of the formed electron and hole traps in the bulk and at surface/interfaces of the perovskite layer from their impact on the performance of the device can be beneficial in optimizing fabrication methods. Here, the transient AC and steady state DC measurements, and morphology characterizations confirm the variation of performance parameters with respect to grain boundaries growth. The device physics is uncovered with respect to the grain size (GS) of the perovskite layer employing the theoretical drift-diffusion framework incorporating the electronic and ionic contributions. The increase of open circuit voltage ( ) for devices with large GS can be associated to the density of defect states. The findings here suggest a more pronounced role of interfaces in efficiency enhancement of the PSCs with the emphasis on the impact of the hole transport layer (HTL)/perovskite layer interface which is also found to be accountable to the difference between the device internal voltage and the terminal voltage and minimizing this difference can lead to an enhancement of approximately 100 mV in . Additionally, the electron traps in the bulk of the perovskite layer play a distinguishable role in the reduction of for the device with the smallest GS. The ionic defect density is also estimated. Considering our results and previous reports, the performance of the PSC is remarkably dependent on the method of fabrication and the associated perovskite conversion mechanism, and not necessarily on GS. The results are expected to deliver important guidelines for the development of more efficient PSCs by further enhancement of the towards its thermodynamic limit of 1.32V, via creating optimal interfaces.

Herein we report the preparation and application of 4 different zinc(II) tetrakis(dihydroxyphenyl) porphyrins (ZnTDHPP) as the sensitizing dyes in dye-sensitized solar cells (DSSCs). The experimental results include solution and solid state UV-Vis data, steady state current–voltage characteristics, and our theoretical analysis comprised of density functional theory (DFT) and Langmuir isotherm adsorption formalism. The results show that the Zn tetrakis(2,3-dihydroxyphenyl) porphyrin (Zn2,3TDHPP) and Zn tetrakis(3,4-dihydroxyphenyl) porphyrin (Zn3,4TDHPP) with adjacent hydroxyl groups attaches to a TiO₂ surface much more strongly than carboxylate. The catechol anchoring group showed high stability of the dye on the TiO₂ surface. The cells prepared from these porphyrins showed no significant desorption of dye from the TiO₂ surface after several days. The DSSCs based on Zn2,3TDHPP showed the best photovoltaic performance under AM 1.5 irradiation comparable to the conventional Zn tetrakis(p-carboxyphenyl) porphyrin (ZnTCPP), despite lower dye loading on the TiO₂ surface. However, non-cooperative OH bonding to TiO₂ for Zn2,4TDHPP and Zn2,5TDHPP shows weak attachment to the TiO₂ surface and lower efficiencies. DFT calculations showed that the Zn2,3TDHPP structure is more non-planar than the others, which may suppress dye aggregation. The adopted adsorption modeling is fitted to the experimental data to study the kinetics of dye loading. The study can herald development of a new class of porphyrin sensitizer for DSSC applications.