Evaluation of photoluminescence quantum yield of monolayer WSe2 using reference dye of 3‐borylbithiophene derivative

We studied an evaluation method of photoluminescence (PL) quantum yield of monolayer transition metal chalcogenides (TMDs) on a transparent substrate using a reference dye. A 3‐borylbithiophene derivative (C58H49BN2S4) reference dye shows a high PL quantum yield of 36% even in the solid form and the high quantum yield is kept in a Poly(methyl methacrylate) (PMMA) matrix. Moreover, the photon energy of PL is similar to those of monolayer TMDs. These PL characteristics of the reference dye are useful for a evaluation of PL quantum yield in monolayer TMDs. The PL quantum yield of 0.18 ± 0.03% was evaluated for mechanically exfoliated monolayer WSe2 on glass substrate at room temperature.