One-step Preparation of ZnO Electron Transport Layers Functionalized with Benzoic Acid Derivatives

We present a "one-step" approach to modify ZnO electron transport layers (ETLs) used in organic solar cells. This approach involves adding benzoic acid (BZA) derivatives directly to the ZnO precursor solution, which are then present at the surface of the resulting ZnO film. We demonstrate this approach for three different BZA derivatives, namely benzoic acid, chlorobenzoic acid, and 4-hydrazinobenzoic acid. For all molecules, improved device performance and stability is demonstrated in solar cells using an active layer blend of PTQ10 (donor) and ITIC-Br (non-fullerene acceptor) compared to such cells prepared using untreated ZnO. Furthermore, similar or improved device performance and stability is demonstrated compared to conventional PEIE treatment of ZnO. The presence of the BZA derivatives at the surface after processing is established using X-ray photoelectron spectroscopy and near-edge X-ray absorption fine-structure spectroscopy. From atomic force microscopy analysis and X-ray diffraction studies, the addition of BZA derivatives appears to restrict ZnO grain growth; however, this does not negatively impact device performance. ZnO layers treated with BZA derivatives also exhibit higher water contact angle and lower work function compared to untreated ZnO. This approach enables simplification of device manufacture while still allowing optimization of the surface properties of metal oxide ETLs. Keywords: electron transport layers, zinc oxide, organic solar cells, surface modificationComment: Manuscript: 25 pages, 8 figures, 5 tables. Supplementary Material: 36 pages, 22 figures, 13 tables. Submitted to Solar Energy Materials and Solar Cell

Polyolefin composition for medium/high/extra high voltage cables comprising benzil-type voltage stabiliser

The present invention relates to a polyolefin composition comprising (A) a polyolefin, (B) a benzil derivative comprising, preferably consisting of, the structural unit according to the following formula (I) wherein R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 independently from each other are hydrogen, or a hydrocarbyl group which may contain heteroatoms or at least two of said R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 together with the ring atoms of the ring system of formula (I) they are attached to, form a further aromatic or non-aromatic ring fused to the ring system of formula (I) and at least R1 or R2 is an ester group. The invention also relates to a wire or cable, in particular a medium, high or extra high voltage cable, comprising such a composition, and to the use of such a composition for the production of a wire or cable, in particular a medium, high or extra high voltage cable

Thioxanthone Derivatives as Stabilizers Against Electrical Breakdown in Cross-Linked Polyethylene for High Voltage Cable Applications

In the search of voltage stabilizers for high voltage underground cables the chemical synthesis and electrical tree inhibiting effect of a series of thioxanthone derivatives in cross-linked low-density polyethylene (XLPE) is reported. The strongest increase in electrical tree initiation field under high-voltage alternating current (HVAC) conditions was 55% compared to reference XLPE after the addition of 0.3 wt% 9-oxo-9H-thioxanthen-2-yl methacrylate. Thermal analysis, small angle X-ray scattering and gel content measurements showed that the addition of the stabilizers did not significantly influence the microstructure and gel fraction of XLPE. A comparison between the stabilizing effects of the thioxanthone derivatives and previously reported photophysical properties revealed that a short lifetime of the triplet excited state can be related to a good voltage-stabilizing effect

Tailored Side-Chain Architecture of Benzil Voltage Stabilizers for Enhanced Dielectric Strength of Cross-Linked Polyethylene

The synthesis and physico-chemical properties of seven benzil-type voltage stabilizers are reported. The benzil core is substituted with alkyl chains of different length that are linked to the benzil core via an ester, ether, or tertiary amine group. All additives can be melt-processed with low-density polyethylene (LDPE). Fourier-transform infrared spectroscopy confirms that benzil compounds are not affected by the LDPE cross-linking reaction induced by dicumyl peroxide. Moreover, a combination of gel content measurements, thermal analysis, and small-angle X-ray scattering indicates that the presence of benzil voltage stabilizers does not significantly alter the microstructure of cross-linked polyethylene (XLPE). Electrical tree inhibition experiments under high-voltage alternating current conditions show that all investigated additives substantially enhance the dielectric strength of the insulating material at a concentration of only 10 mmol kg−1. The highest improvement in dielectric strength, of more than 70% with respect to reference XLPE, is obtained with voltage stabilizers, which carry short (methyl) side chains that are linked to the benzil core via an ester or tertiary amine group