Efficient charge generation from triplet excitons in metal-organic heterojunctions
Abstract
The success of many emerging molecular electronics concepts hinges on an atomistic understanding of the underlying electronic dynamics. We employ picosecond time-resolved x-ray photoemission spectroscopy (tr-XPS) to elucidate the roles of singlet and triplet excitons for photoinduced charge generation at a copper-phthalocyanine-C60 heterojunction. Contrary to common belief, fast intersystem crossing to triplet excitons after photoexcitation is not a loss channel but contributes to a significantly larger extent to the time-integrated interfacial charge generation than the initially excited singlet excitons. The tr-XPS data provide direct access to the diffusivity of the triplet excitons DCuPc=(1.8 ±1.2 ) ×10-5c m2/s (where CuPc is copper-phthalocyanine) and their diffusion length Ldiff=(8 ±3 ) nm .
- Publication:
-
Physical Review B
- Pub Date:
- January 2019
- DOI:
- 10.1103/PhysRevB.99.020303
- Bibcode:
- 2019PhRvB..99b0303R