title: Ultrafast Coherent Electron-Hole Separation Dynamics in a Fullerene Derivative.
abstract: The use of fullerene derivatives as electron donors in bulk heterojunctions is a promising development in the search for efficient energy conversion in hybrid solar cells. A long-lived photoexcited electron-hole pair will give rise to increased efficiency in photoenergy conversion. One way to prevent fast electron-hole recombination is to engineer fullerene derivatives that exhibit intrinsic electron-hole separation through accessible charge-transfer excited states. In this letter, the dynamics of photoexcited electron-hole pairs in a C60 derivative is studied using the real-time time-dependent density functional theory. Although the charge-transfer excited state is not directly accessible from the ground state, intrinsic coherent electron-hole separation is observed following photoexcition as a result of direct coupling between excited states. Ultrafast charge-transfer dynamics is the dominant phenomenon in <60 fs after visible photoexcitation. This work provides insights into the characteristics of ultrafast dynamics in photoexcited fullerene derivatives, and aids in the rational design of efficient solar cells.
authors: Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
authors: Craig T
authors: CT
authors: Chapman
authors: Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
authors: Wenkel
authors: W
authors: Liang
authors: Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
authors: Xiaosong
authors: X
authors: Li
keywords: TDDFT; charge transfer; electron−hole dynamics; fullerene