QUENCHING OF PHOTOLUMINESCENCE FROM POROUS SILICON BY AROMATIC-MOLECULES

A systematic study of the efficiency of photoluminescence (PL) quenchi ng of nanocrystalline porous Si by aromatic triplet energy accepters w as carried out. The effects of molecular triplet energy, molecular siz e, and the porous Si emission energy on PL quenching efficiency were p robed. Photoluminescent porous Si samples, prepared by electrochemical etch, were titrated with toluene solutions of anthracene, 9,10-diphen ylanthracene, 9,10-dichloroanthracene, 9,10-dimethylanthracene, pyrene , 1,2-benzanthracene, acridine, and 1,4-diphenyl-1,3-butadiene, and th e steady-state and time-resolved PL spectra were measured. The quenchi ng of PL adequately fits a dynamic Stern-Volmer quenching model. The r ate of quenching increases with increasing exoergicity, and then level s off at higher exoergicities. The mechanism of quenching is attribute d to energy transfer from the porous Si excited state to the triplet l evels of the quencher molecules. The rate of quenching can also be aff ected by the size of substituents on the quenchers; some molecules wit h larger substituents display slower quenching rates than expected fro m their triplet energies.