Ambient Phosphor with High Efficiency and Long Lifetime in Poly(Methyl Methacrylate) Through Charge-Transfer-Mediated Triplet Exciton Formation for Photolithography Applications

Currently, purely organic compounds showing ambient phosphorescence with high efficiency (phi P) and ultra-long lifetime (tau P) are quite rare and often need to be achieved in hydrophilic poly(vinyl alcohol)-based hosts. This severely limits their applications. Here, we provide a solution to this issue by constructing an ortho-linked donor-acceptor (D-A) dyad whose D moiety has not only a long-lived T1 state to achieve a long tau P, but also a Tn state that is close to the S1 state of the dyad to trigger effective spin-orbit charge transfer intersystem crossing (SOCT-ISC). The rationality of this strategy was validated by a new phosphor OF-BCz that is able to show a tau P of 1.92 s and a phi P of 30 % even in a less rigid matrix of poly(methyl methacrylate) (PMMA). Excitingly, OF-BCz exhibited its potential as both a photocuring initiator and an in situ quality indicator, allowing for the visual detection of defects in photolithographic patterning. Through spin-orbit charge transfer intersystem crossing (SOCT-ISC) strategy, a new ortho-linked donor-acceptor dyad OF-BCz showing a long lifetime (tau P) of 1.92 s and a high efficiency (phi P) up to 30 % in PMMA matrix, was constructed. Thanks to its excellent performance and high triplet energy level (ET1), OF-BCz was successfully applied in photolithography as a photoinitiator and an in situ quality indicator.+image