Effect of multi-armed triphenylamine-based hole transporting materials for high performance perovskite solar cells

A series of hole-transporting materials (HTMs) based on [2,2]paracyclophane and triphenyl-amine (TPA) was synthesized. We studied the effect of the chemical structure of the HTM on the photovoltaic performance of perovskite solar cells by varying the number of TPA charge transporting components in the HTM. Tetra-TPA, in which four TPAs are incorporated into the [2,2]paracyclophane core, exhibited better hole transport properties than di-TPA and tri-TPA, which contain two and three TPAs, respectively. In particular, incorporation of the TPA group with a multi-armed structure effectively enhanced the conductivity of the HTM layer in the out-of-plane direction in the solar cell device. Due to the improved charge transport and appropriate molecular energy levels of tetra-TPA, the perovskite solar cell based on the tetra-TPA HTM achieved higher Jsc and FF values than the devices based on di-TPA and tri-TPA HTMs, with a high solar cell efficiency (17.9%).

Chiral Brønsted acid from a cationic gold(I) complex: catalytic enantioselective protonation of silyl enol ethers of ketones

A chiral Brønsted acid has been developed from a cationic gold(I) disphosphine complex in the presence of alcoholic solvent and applied to the enantioselective protonation reaction of silyl enol ethers of ketones. Various optically active cyclic ketones were obtained in excellent yields and high enantioselectivities, including cyclic ketones bearing aliphatic substrates at the α-position. Furthermore, the application of this Brønsted acid was extended to the first Brønsted acid-catalyzed enantioselective protonation reaction of silyl enol ethers of acyclic substrates, regardless of their E/Z ratio.

Development of a new Lewis base-tolerant chiral LBA and its application to catalytic asymmetric protonation reaction

A new Lewis base-tolerant LBA (Lewis Acid Assisted Brønsted Acid) derived from La(OTf)(3) and (S)-HOP has been developed as a new chiral Brønsted acid. This acid has been successfully applied as a catalyst to asymmetric protonation reactions of silyl enol ethers of 2-substituted cyclic ketones.

N-triflylthiophosphoramide catalyzed enantioselective Mukaiyama aldol reaction of aldehydes with silyl enol ethers of ketones

The first Brønsted acid catalyzed asymmetric Mukaiyama aldol reaction of aldehydes using silyl enol ethers of ketones as nucleophiles has been reported. A variety of aldehydes and silyl enol ethers of ketones afforded the aldol products in excellent yields and good to excellent enantioselectivities. Mechanistic studies revealed that the actual catalyst may be changed from the silylated Brønsted acid to the Brønsted acid itself depending on the reaction temperature.

A Brønsted acid catalyst for the enantioselective protonation reaction

A highly reactive and robust chiral Brønsted acid catalyst, chiral N-triflyl thiophosphoramide, was developed. The first metal-free Brønsted acid catalyzed enantioselective protonation reaction of silyl enol ethers was demonstrated using this chiral Brønsted acid catalyst. The catalyst loading could be reduced to 0.05 mol % without any deleterious effect on the enantioselectivity.