Proton nuclear magnetic resonance (1H NMR) of flammable organic chemicals in radioactive high-level supernatant waste at the Savannah River Site (SRS)

The Savannah River Site stores approximately 36 million gallons of radioactive and hazardous waste that contains approximately 245 million curies. The waste is sent through various chemical processes to reduce its volume and to separate various components. The facility plans to replace formic acid (a chemical used to reduce soluble mercury) with glycolic acid. Recycle solution with glycolate may flow back to the tank farm, where the glycolate can generate hydrogen gas by thermal and radiolytic mechanisms. The current analytical method for detecting glycolate (ion chromatography) in supernatant requires a large dilution to reduce interference from the nitrate anions. Hydrogen nuclear magnetic resonance is an analytical method that requires less sample dilution. It takes advantage of the CH₂ group in glycolate. Liquid samples were spiked with four different levels of glycolate to build a calibration line, as it is recommended in the standard addition method. The detection and quantitation limits determined were 1 and 5 ppm, respectively, for 32 scans, which is well below the process limit of 10 ppm. In one test, 800 scans of a supernatant spiked with 1 ppm glycolate resulted in a -CH₂ peak with a signal-to-noise ratio of 36.

Phenoxy-(Chloro) n -Boron Subnaphthalocyanines: Alloyed Mixture, Electron-Accepting Functionality, and Enhanced Solubility for Bulk Heterojunction Organic Photovoltaics

The first set of phenoxy BsubNc compounds, PhO-Cl n BsubNc and F5-Cl n BsubNc, was synthesized through an axial displacement reaction of Cl-Cl n BsubNc with phenol and pentafluorophenol (respectively). Like their precursor, the products were found to be an alloyed mixture of phenoxylated Cl n BsubNcs with random positioning in the solid state yet consistent frequency of bay position chlorination. The average bay position chlorine occupancy was determined to be 0.99 through single crystal diffraction of PhO-Cl n BsubNc. Although the phenoxylation of Cl-Cl n BsubNc did not influence the chromophore photophysical properties, the electrochemical behavior was found to be more stable. Phenoxylation yielded differences in organic photovoltaic (OPV) device metrics. Specifically, a significant increase in open circuit voltage (V OC) was observed, ultimately exceeding 1.0 V when phenoxylated Cl n BsubNcs were paired with alpha-sexithiophene (α-6T) in planar heterojunction OPVs. Phenoxylation enabled the first example of BsubNcs incorporated into polymer-based bulk heterojunction (BHJ) OPVs through enhanced solubility. Phenoxylated Cl n BsubNcs, when paired with poly-3-hexylthiophene, also showed high V OC in BHJ OPVs with broad spectral absorption up to 760 nm. In the BHJ case, simple phenoxy was shown to be a better axial substituent compared to pentafluorophenoxy. This study represents the first example of using Cl n BsubNcs with nonchlorine axial substituents in OPVs and demonstrates that phenoxylation has a significant impact on device metrics while enhancing solubility to enable incorporation of Cl n BsubNcs into BHJ OPVs.

Asymmetrical Squaraines Bearing Fluorine-Substituted Indoline Moieties for High-Performance Solution-Processed Small-Molecule Organic Solar Cells

Two novel asymmetrical squaraines based on the indoline unit, ASQ-5-F and ASQ-5-DF, with one and two fluorine substituents, have been developed to investigate the effect of fluorine substituted on small-molecule bulk-heterojunction (BHJ) organic solar cells (OSCs). In comparison with non-fluorine-substituted ASQ-5, both fluorine-substituted ASQ-5-F and ASQ-5-DF possess analogous absorption band gaps but 0.05 and 0.10 eV lowered highest occupied molecular orbital (HOMO) energy levels, respectively. Single-crystal analysis exhibits that ASQ-5-DF shows more desirable intermolecular packing patterns for the hole-carrier collection than ASQ-5 does; hence, higher hole mobility could be acquired. Therefore, solution-processed small-molecule BHJ OSCs fabricated with ASQ-5-F/PC71BM and ASQ-5-DF/PC71BM blends exhibit extremely higher power conversion efficiency (PCE; 5.0% and 6.0%, respectively) than that of ASQ-5/PC71BM (4.5%). The much improved PCE could be attributed to the simultaneously enhanced Voc, Jsc, and FF relative to those of the ASQ-5-based device. To our knowledge, this is the highest PCE (6.0%) among squaraine-based solution-processed BHJ OSCs and the highest PCE in OSCs based on the fluorinated donor segment of small molecules.

Development of asymmetrical near infrared squaraines with large Stokes shift

New asymmetrical squaraines with large Stokes shifts of up to 90 nm were synthesized. TDDFT calculations indicate that steric effects from N,N-dibutylaniline and squaraine contribute to the large geometric change, resulting in the large Stokes shift.

Axially phenoxylated aluminum phthalocyanines and their application in organic photovoltaic cells

Phenoxylation of chloro aluminum phthalocyanine (Cl-AlPc) can be easily achieved only when using “acidic phenols”. Once incorporated into unoptimized organic photovoltaics (OPVs) the result is an increase in the V_OC.

Asymmetrical squaraines for high-performance small-molecule organic solar cells with a short circuit current of over 12 mA cm−2

Asymmetrical squaraine dyes with two aryl groups directly linked to the squaric acid core were synthesized, and exhibited excellent photovoltaic performance.

Additive-assisted control over phase-separated nanostructures by manipulating alkylthienyl position at donor backbone for solution-processed, non-fullerene, all-small-molecule solar cells

A non-fullerene, all-small-molecule solar cell (NF-SMSC) device uses the blend of a small molecule donor and a small molecule acceptor as the active layer. Aggregation ability is a key factor for this type of solar cell. Herein, we used the alkylthienyl unit to tune the aggregation ability of the diketopyrrolopyrrole (DPP)-based small molecule donors. Replacing two alkoxyl units in BDT-O-DPP with two alkylthienyl units yields BDT-T-DPP, and further introducing another two alkylthienyl units into the backbone produces BDT-T-2T-DPP. With the introduction of alkylthienyl, the backbone becomes twisted. As a result, the ππ-stacking strength, aggregation ability, and crystallite size all obey the sequence of BDT-O-DPP > BDT-T-DPP > BDT-T-2T-DPP. When selected a reported perylene diimide dimer of bis-PDI-T-EG as acceptor, the best NF-SMSC device exhibits a power conversion efficiency of 1.34, 2.01, and 1.62%, respectively, for the BDT-O-DPP, BDT-T-DPP, and BDT-T-2T-DPP based system. The BDT-T-DPP/bis-PDI-T-EG system yields the best efficiency of 2.01% among the three combinations. This is due to the moderate aggregation ability of BDT-T-DPP yields moderate phase size of 30-50 nm, whereas the strong aggregation ability of BDT-O-DPP gives a bigger size of 50-80 nm, and the weak aggregation ability of BDT-T-2T-DPP produces a smaller size of 10-30 nm. The BDT-T-DPP/bis-PDI-T-EG combination exhibits balanced hole/electron mobility of 0.022/0.016 cm(2)/(V s), whereas the BDT-O-DPP/bis-PDI-T-EG and the BDT-T-2T-DPP/bis-PDI-T-EG blend show a hole/electron mobility of 0.0011/0.0057 cm(2)/(V s) and 0.0016/0.11 cm(2)/(V s), respectively.

A low bandgap asymmetrical squaraine for high-performance solution-processed small molecule organic solar cells

A low-bandgap asymmetrical squaraine ASQ-5 bearing an indoline substituent for solution-processed organic solar cells with high J_sc and PCE was synthesized.