In-situ grafting N-arylcarbazoles enables more ultra-long room temperature phosphorescence polymers

Abstract

N-Arylcarbazole derivatives have been proven to be applicable dopants for organic room temperature phosphorescence (RTP) polymers. Here we present for the first time that their structure modification enables highly-efficient and more ultra-long RTP. Three N-phenylcarbazole derivatives (CZPA, CZBM, and CZBA) containing boronic acid, formamide, and carboxyl units are doped into polyvinyl alcohol (PVA) by thermoplasticizing solution-cast films. PVA/CZBA and PVA/CZBM sheets show highly-level balanced RTP efficiencies (13.7–17.8 %) and lifetimes (1.79–1.97 s), and PVA/CZPA sheets exhibit ultralong RTP lifetimes of 2.36–3.21 s and commendable RTP efficiencies of 3.6–6.1 % under 365 nm light excitation. To our knowledge, the current doped polymer films with similar RTP lifetimes are almost excited by deep UV light, and N-arylcarbazoles have never been developed as so excellent dopants for ultra-long RTP polymers. The greatly improved RTP properties are attributed to the dual effect of extra n-π* transition and chemical grafting of boronic acid onto PVA chains, which not only enhances triplet population but also inhibits non-radiative relaxation. This work opens up an effective molecular and processing strategy for enhancing RTP properties of organic doped polymers.