The absorption of a single photon produces two triplet excitons in a process called singlet fission. A singlet fission material (A) absorbing at short wavelength may be combined with a conventional material (B) absorbing at longer wavelength for solar energy conversion with efficiency theoretically exceeding the Shockley-Queisser limit. The success of this strategy relies on the collection of charges from the two triplet excitons in (A) as well as from the single exciton in (B). Here we demonstrate strategies for the implementation of this strategy via either charge or energy transfer. In the first example, we show the competitive one and two-electron transfer from the singlet-triplet pair quantum superposition formed from optical excitation of tetracene to the LUMO+1 and LUMO levels in C60, respectively. In the second example, we demonstrate the transfer of triplet excitons in tetracene to a second electron donor, CuPc, in competition with charge separation and recombination. We discuss stringent requirements for the harvesting of charge or energy from singlet fission for efficient solar energy conversion.

Harvesting singlet fission for solar energy conversion: Charge vs. energy transfer

246th National Meeting (2013)

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