Precisely defined triphenylamine-based hole-transporting polymers via living anionic polymerization for high-performance perovskite LEDs

초록

The anionic polymerization of 4-vinyltriphenylamine (A) and N,N-bis([1,1 '-biphenyl]-4-yl)-4 '-ethenyl[1,1 ' biphenyl]-4-amine (B), which incorporate triphenylamine-based hole-transporting units, was successfully performed in tetrahydrofuran at - 30 degrees C using potassium naphthalenide and sec-butyllithium as initiators. Both monomers underwent complete polymerization within 2 min, affording poly(A) and poly(B) with precisely controlled molecular weights (Mn = 5.6-61.6 kg/mol) and narrow molecular weight distributions (Mw/Mn <= 1.18). The living character of the propagating chain ends in poly(A) and poly(B) was verified by postpolymerization under identical conditions, and the copolymerizability of A and B was further assessed via block copolymerization with styrene. Thermal analyses of poly(A) and poly(B) using thermogravimetric analysis and differential scanning calorimetry demonstrated that both polymers exhibit high thermal stability and high glass transition temperatures. The solvent resistance of poly(A) and poly(B) films toward n-hexane, used for perovskite thin film deposition, was evaluated by rinsing tests and surface morphology analyses, enabling their application as hole-transporting layers (HTLs) in solution-processed perovskite light-emitting diodes (PeLEDs). PeLEDs fabricated with poly(A) and poly(B) as HTLs exhibited superior device performance compared with device employing poly(9-vinylcarbazole) as a reference HTL. In particular, poly(B)-based PeLEDs showed the highest current efficiency (eta CE, max = 68.3 cd/A) and maximum external quantum efficiency (eta EQE, max = 15.8 %), which can be attributed to the effective interfacial defect passivation provided by poly(B) and its well-balanced HOMO energy level between the hole injection layer and the emitting layer.

키워드