A Molecular Design Principle for Pure-Blue Light-Emitting Polydiarylfluorene with Suppressed Defect Emission by the Side-Chain Steric Hindrance Effect

Abstract

Functional side chains of light-emitting conjugated polymers (LCPs) play critical roles in the photophysical, electronic, and mechanical performances of the solution-processed polymer light-emitting diodes (PLEDs). Herein, we reported a molecular design principle of polydiarylfluorenes for realizing pure-blue light emission that is introducing functional side chains containing carbazole and amide groups. Resulting from the steric hindrance effect of carbazole groups, the hydrogen bond interactions among the side-chain amide groups were destroyed. As a consequence, both solution-processed films and PLEDs based on such films presented pure-deep-blue emission with the Commission International de L’Eclairage (CIE) coordinates of (0.15, 0.10) and (0.17, 0.14), respectively. Time-resolved transient spectroscopy revealed their similar exciton behaviors in film excited states, and the ultrafast energy transfer occurred within tens of picoseconds. These insights enable us a deeper understanding about the influence of functional side chains on the optoelectronic properties and supply a feasible design strategy for high-performance conjugated polymers.

Blue light-emitting conjugated polymer with low modulus and better EL spectra stability

“…[17][18][19] However, owing to the nature of the wide band gap, devices' color purity is susceptible to internal defects induced by interchain aggregates or device operation. [20][21][22] This is why some reported strategies for stretchable devices inevitably manifested or aggravated defect emission in the electroluminescence (EL) spectra of polyfluorene-based blue light-emitting diodes. 23,24 Therefore, although significant progress has been made in stretchable semiconductor devices such as organic field-effect transistors (OFET) and polymer solar cells (PSC), 10,[25][26][27] considerable challenges still remain in developing stretchable blue LCPs, which seriously restrict their practical application in flexible displays.…”

Large‐Area Printed Display Based on Green Solvent Processable Blue Light‐Emitting Conjugated Polymer

“…[26][27][28][29] However, research on the ecofriendly solvent-processed polymer light-emitting diodes (PLEDs) has been rarely reported due to the limited solubility of LCPs resulted by rigid aromatic backbone and complex intermolecular interactions, [30] especially for the blue PLEDs, [31] where achieving high-efficient and stable electroluminescence (EL) remain huge challenges. [32][33][34] On the other hand, although the classification and ranking of green solvents varies slightly from organization to organization, they all make qualitative assessment according to the criteria: low health hazard, high safety, and small environmental impact. [35,36] From this perspective, bio-based solvents seem like to be one of the ideal choices for solution-based printed electronics.…”