Direct Measurement of the Triplet Quantum Yield of Poly(3-dodecylthiophene) in Solution

Abstract

The photophysics, including radiative and nonradiative quantum yields and decay rates, of regioregular poly(3-dodecylthiophene) (P3DT) in benzene were studied by means of UV−visible spectroscopy, photoluminescence spectroscopy, photothermal beam deflection (PBD), photoacoustic calorimetry (PAC), and time-resolved photoluminescence spectroscopy. We observe the fluorescence quantum efficiency to be 0.30 ± 0.01 and the internal conversion (from S1 to S0) quantum yield of 0.59 ± 0.02 as well as the intersystem crossing (from S1 to T1) quantum yield of 0.11 ± 0.01. By measuring the fluorescence lifetime of ca. 490 ps, we estimate a radiative lifetime of 1.64 ns for the singlet excitons and nonradiative decay rate constants of kic = 1.21 ns-1 and kisc = 0.22 ns-1 for internal conversion and intersystem crossing, respectively. The nature and photophysics of triplet states in poly(3-dodecylthiophene) are well characterized using PBD and PAC, and the result suggests that internal conversion plays a major role in energy depletion.