Observation of Two Triplet-Pair Intermediates in Singlet Exciton Fission.
Singlet fission is an excitation multiplication process in molecular systems that can circumvent energy losses and significantly boost solar cell efficiencies; however, the nature of a critical intermediate that enables singlet fission and details of its evolution into multiple product excitations remain obscure. We resolve the initial sequence of events comprising the fission of a singlet exciton in solids of pentacene derivatives using femtosecond transient absorption spectroscopy. We propose a three-step model of singlet fission that includes two triplet-pair intermediates and show how transient spectroscopy can distinguish initially interacting triplet pairs from those that are spatially separated and noninteracting. We find that the interconversion of these two triplet-pair intermediates is limited by the rate of triplet transfer. These results clearly highlight the classical kinetic model of singlet fission and expose subtle details that promise to aid in resolving problems associated with triplet extraction.
Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States.
Ryan D
RD
Pensack
Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States.
Evgeny E
EE
Ostroumov
Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada.
Andrew J
AJ
Tilley
Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States.
Samuel
S
Mazza
Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
Christopher
C
Grieco
Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States.
Karl J
KJ
Thorley
Department of Chemistry, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
John B
JB
Asbury
Department of Chemistry, University of Toronto , Toronto, Ontario M5S 3H6, Canada.
Dwight S
DS
Seferos
Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506, United States.
John E
JE
Anthony
Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States.
Gregory D
GD
Scholes