Comparative Study of Exciton Relaxation Dynamics in C60 and C70 Solid

• Published in: The journal of physical chemistry. B 1999-08, Vol.103 (31), p.6504-6508
• Main Authors: Cho, Hyun Sun, Yang, Sung Ik, Kim, Seong Keun, Shin, Eun-joo, Kim, Dongho
• Format: Article
• Language: English
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp991252t

The exciton dynamics of C70 solid has been investigated by the time-resolved photoluminescence (PL) and transient absorption (TA) technique and compared with the case of C60 solid. Three distinct PL bands were observed at 685, 715, and 740 nm. The high-energy band at 685 nm displayed an almost purely single-exponential decay profile, while the other two exhibited a slow-decaying tail as well, especially at low temperatures. Laser fluence dependence of PL decay profiles shows that the decay in C70 solid, in contrast to the case of C60, is predominantly governed by fast (20 ps) nonradiative exciton-trap annihilation, with the intersystem crossing playing a minor role in lower energy bands at 715 and 740 nm. On the other hand, laser fluence dependence of transient absorption signals shows that the decay in C70 is much faster than PL decay, which indicates the fast component arises from the exciton−exciton annihilation process under extremely high laser fluence condition.