Cross-Conjugated n-Dopable Aromatic Polyketone

Dopant-Free Crossconjugated Hole-Transporting Polymers for Highly Efficient Perovskite Solar Cells

Currently, there are only very few dopant-free polymer hole-transporting materials (HTMs) that can enable perovskite solar cells (PVSCs) to demonstrate a high power conversion efficiency (PCE) of greater than 20%. To address this need, a simple and efficient way is developed to synthesize novel crossconjugated polymers as high performance dopant-free HTMs to endow PVSCs with a high PCE of 21.3%, which is among the highest values reported for single-junction inverted PVSCs. More importantly, rational understanding of the reasons why two isomeric polymer HTMs (PPE1 and PPE2) with almost identical photophysical properties, hole-transporting ability, and surface wettability deliver so distinctly different device performance under similar device fabrication conditions is manifested. PPE2 is found to improve the quality of perovskite films cast on top with larger grain sizes and more oriented crystallization. These results help unveil the new HTM design rules to influence the perovskite growth/crystallization for improving the performance of inverted PVSCs.

Synthesis, Optical and Electrochemical Properties of High-Quality Cross-Conjugated Aromatic Polyketones

This paper describes the synthesis and characterization of three new aromatic polyketones with repeating units based on 2,2'-(2,5-dihexyl-1,4-phenylene) dithiophene (PTK), 2,2'-(9,9-dihexyl-9H-fluorene-2,7-diyl)dithiophene (PFTK), and 4,7-bis(3-hexylthiophen-2-yl)benzo[c][1,2,5]thiadiazole (PBTK). These polymers were obtained with a one-pot Suzuki-Miyaura cross-coupling-promoted homopolymerization to afford high-quality, defect-free polymers. Experimental and theoretical studies were applied to investigate their optical and electrical properties. The cross-conjugated nature of aromatic polyketones imparts excellent thermal stability. Exposure to acid converts the cross-conjugation to linear-conjugation, enabling the dynamic tuning of optoelectronic properties.

Rendering cross-conjugated azophenine derivatives emissive to probe the silent photophysical properties of emeraldine

An azophenine derivative was synthesized by coupling truxene and azophenine via the copper-free Sonagashira reaction using Pd₂(dba)₃ and As(PPh)₃ as catalysts. The crystal structure of this heavy azophenine model (∼4000) was made and the identity of the structure was confirmed. By introducing truxene groups into this cross-conjugated structure, the deactivating rotations around the NH-C₆H₄ bonds were slowed down, which rendered this derivative near-IR emissive at 298 K. This species provided then the appropriate spectral and kinetic signatures for knowing where and what to look for in emeraldine, which was called non-emissive. Besides, two other compounds were also synthesized as models for this azophenine derivative for comparison and interpretation purposes.

The effect of the backbone structure on the thermoelectric properties of donor–acceptor conjugated polymers

This work illustrated a relationship between backbone structure and thermoelectric properties through a study of three donor–acceptor (D–A)-structured conjugated polymers.