Four visible light triphenylamine-based oxime ester photoinitiators (TP-1–4) were synthesized and confirmed successfully through ¹H NMR, ¹³C NMR, and electron impact mass spectrometry (EI-MS) measurements as well as elementary analyses (EA). The design strategy for triphenylamine substituted photoinitiators involved the use of hydrogen atoms only for TP-1, one methoxy group for TP-2, two methoxy groups for TP-3 and two methyl groups for TP-4. The incorporation of triphenylamine derivatives in oxime esters gives near UV and visible light absorption characters with maximum absorption peaks at around 360 nm. Upon using a UV lamp as an irradiation source, all the oxime esters showed good double bond conversion efficiency in a range of 72–92% in the free radical polymerization of trimethylolpropane triacrylate (TMPTA) through photo-DSC experiments. Among all, TP-1 displayed the highest final conversion efficiency. Accordingly, the photochemical reaction behavior was studied using photolysis, cyclic voltammograms (CV), electron spin resonance (ESR) and theoretical calculations. Additionally, selected photoinitiating systems exhibited outstanding 3D patterns with high resolution and good edge definition through direct laser write (DLW) experiments @405 nm. This work thus demonstrates a judicious chemical design to fine-tune the photopolymerization character in triphenylamine oxime ester analogues.

In this study, three triphenylamine-based hexaarylbiimidazole (HABI) derivatives featuring different numbers of methoxy groups (none for HABI1, two for HABI2, and four for HABI3) have been synthesized. For comparison, a common hydrogen acceptor photoinitiator, ocl-HABI (2-chlorohexaarylbiimidazole), was also applied to compare the corresponding properties. The new HABIs displayed a more red-shifted and higher molar extinction coefficient than ocl-HABI with the absorption region extended to visible light. A larger free radical concentration of HABIs was also achieved, which was confirmed via electron paramagnetic resonance (ESR) spectroscopy. These visible light-sensitive HABIs or ocl-HABI in combination with a suitable hydrogen donor, i.e., N-phenyl glycine (NPG) were utilized as photoinitation systems for conventional radical polymerization (RDRP). All the packages exhibited good electron-transfer ability by the calculation of the free energy changes (ΔG_ET). The HABI1/NPG system exhibited the best double bond conversion efficiency and outperformed the corresponding ocl-HABI/NPG-based formulation under similar UV light source testing conditions. We then employed the HABI1/NPG and ocl-HABI/NPG systems for LED light source testing. Again, HABI1/NPG had better photocuring conversion efficiency and shorter time at maximum heat flow than ocl-HABI/NPG, indicating that the HABI1/NPG system can be applied to light curing applications under different light sources, such as UV and LED.

In this review we cover the current progress on multi-anchored sensitizers for dye-sensitized solar cells, including the variation of the molecular structure, type of anchor (cyanoacrylic acid, carboxylic acid, rhodanine-3-acetic acid and pyridyl anchors via a type I indirect electron injection mechanism; catechol anchors via a type II indirect electron injection mechanism; and hybrid anchors), and variation of the number of anchors. The influence of these structural variations on the cell performance is discussed.