Flexible narrowband organic photodiode with high selectivity in color detection.

This study describes the design of a flexible narrowband organic photodiode (OPDs) with a novel structure. A bulk heterojunction of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM) is introduced as a photoactive layer, with an optimized thickness of 160 nm, and a MoO3/Ag/MoO3 (MAM) multilayer electrode and polyimide (PI) film substrate were used. The OPD with the device architecture of PI/MAM/P3HT:PC70BM/Al showed narrowband photodiode performance in the 500-650 nm wavelength range. The maximum external quantum efficiency (EQE) of the OPD was 15.41% at 570 nm, which dropped to ∼0% outside the operation wavelength range. This narrowband detectivity originated from the cutoff of light at wavelengths below 500 nm by the PI substrate and photoreactivity of P3HT:PC70BM at wavelengths between 300 and 650 nm. Outer bending tests performed over 1000 cycles revealed that the average maximum EQE remained at ∼15%. The maximum responsivity of the OPD was calculated to be 0.07 A W-1 at 570 nm. The OPD device showed a narrow response spectrum with a full width at half maximum of 100 nm. This research suggests a new approach for the fabrication of flexible OPDs with high selectivity in color detection.

Moisture Effect on Particulate Matter Filtration Performance using Electro-Spun Nanofibers including Density Functional Theory Analysis.

In this study, we use density functional theory (DFT) calculations to investigate the effect of moisture on the performance of three types of nanofiber (NF)-based air-filter media prepared by electrospinning polyvinyl alcohol, polyvinylidene fluoride, and polyacrylonitrile (PAN). Based on the DFT calculations of the intermolecular interactions between the NF-based filter media and water molecules, the PAN-NF filter is expected to exhibit the best performance in the wet state. Experiment studies also successfully demonstrate that the PAN-NF filter medium has better performance in the filtration of particulate matter (PM) than a commercial semi-high efficiency particulate air filter under wet conditions, and these results are in good agreement with the DFT calculation. The PAN-NF filter shows better performance because of its hydrophilic nature and the relatively low thickness the filter medium that allowed fast recovery of its PM-filtration performance.

Morphology-Controlled High-Efficiency Small Molecule Organic Solar Cells without Additive Solvent Treatment.

This paper focuses on nano-morphology-controlled small-molecule organic solar cells without solvent treatment for high power-conversion efficiencies (PCEs). The maximum high PCE reaches up to 7.22% with a bulk-heterojunction (BHJ) thickness of 320 nm. This high efficiency was obtained by eliminating solvent additives such as 1,8-diiodooctane (DIO) to find an alternative way to control the domain sizes in the BHJ layer. Furthermore, the generalized transfer matrix method (GTMM) analysis has been applied to confirm the effects of applying a different thickness of BHJs for organic solar cells from 100 to 320 nm, respectively. Finally, the study showed an alternative way to achieve high PCE organic solar cells without additive solvent treatments to control the morphology of the bulk-heterojunction.

High-Performance, Fullerene-Free Organic Photodiodes Based on a Solution-Processable Indigo.

A solution-processable dibromoindigo with an alkyoxyphenyl solubilizing group is developed and used as a new electron acceptor in organic photodiodes. The solution-processed fullerene-free organic photodiodes show an almost spectrally flat response with a high responsivity (0.4 A W(-1)) and a high detectivity (1 × 10(12) Jones). These values are comparable to silicon-based photodiodes.

Optical modeling-assisted characterization of dye-sensitized solar cells using TiO2 nanotube arrays as photoanodes.

Photovoltaic characteristics of dye-sensitized solar cells (DSSCs) using TiO2 nanotube (TNT) arrays as photoanodes were investigated. The TNT arrays were 3.3, 11.5, and 20.6 µm long with the pore diameters of 50, 78.6, and 98.7 nm, respectively. The longest TNT array of 20.6 µm in length showed enhanced photovoltaic performances of 3.87% with significantly increased photocurrent density of 8.26 mA·cm(-2). This improvement is attributed to the increased amount of the adsorbed dyes and the improved electron transport property with an increase in TNT length. The initial charge generation rate was improved from 4 × 10(21) s(-1)·cm(-3) to 7 × 10(21) s(-1)·cm(-3) in DSSCs based on optical modelling analysis. The modelling analysis of optical processes inside TNT-based DSSCs using generalized transfer matrix method (GTMM) revealed that the amount of dye and TNT lengths were critical factors influencing the performance of DSSCs, which is consistent with the experimental results.