Sensitivity boosting in solid-state NMR of thin organic semiconductors by a paramagnetic dopant of copper phthalocyanine

摘要

Sensitivity enhancements in cross-polarization magic-angle-spinning (CPMAS) solid-state NMR spectra of organic thin-film semiconductors are reported. A vacuum-deposited paramagnetic dopant on the semiconductor films reduces ~1H T_1 relaxation time, enabling faster repetition of NMR measurements. When the thickness of the films is between 50 and 100 nm, ~1H spins are well polarized by ~1H-~1H spin diffusion, giving the maximum sensitivity without harmful effects such as paramagnetic shift, broadening, and quenching of CPMAS signals. The binary films of copper phthalocyanine (CuPc) and phenyldipyrenylphosphine oxide (POPy _2) show a threefold reduction of the NMR measurement time.