Organic semiconductor LEDs and solar cells: the role of spin
Event details
| Date | 08.04.2013 |
| Hour | 13:15 |
| Speaker |
Richard Friend University of Cambridge Bio : Richard Friend is the Cavendish Professor of Physics in the University of Cambridge. He has developed the semiconductor physics of pi-conjugated organic polymers, and his research group has demonstrated that these materials can be used in wide range of semiconductor devices, including light-emitting diodes and transistors. He co-founded Cambridge Display Technology Ltd in 1992 to develop light-emitting diode displays, Plastic Logic Ltd in 2000, to develop polymer transistor circuits that are now being developed as flexible active-matrix backplanes for e-paper displays, and Eight-19 Ltd in 2010 to develop plastic solar cells. |
| Location | |
| Category | Conferences - Seminars |
Excitons in molecular semiconductors generally show high Coulomb binding energies, of order 0.5 eV, because dielectric screening is low. They also show comparable values for the exchange energy between spin-singlet and spin-triplet configurations. These both present challenges and opportunities for the use of such materials in both light-emitting diodes and also in solar cells. Non-geminate electron-hole collisions in organic semiconductor diodes should produce 25% spin singlet events and 75% spin triplet events. For systems designed to operate as LEDs, triplet excitons can decay efficiently through triplet-triplet collisions to produce an emissive singlet exciton. Large exchange energies allow scope for multiple exciton generation for materials for which the triplet exciton energy is less than one half of the singlet exciton energy, since this favours energetically the fission of a photogenerated singlet to a pair of triplet excitons. If this process can be used in tandem with a lower energy gap semiconductor that harvests singlet excitons directly then this may enhance solar energy conversion beyond the single-junction Shockley-Queisser limit. We have shown that this can be achieved using a pentacene/lead selenide hybrid solar cell device structure.
Practical information
- General public
- Free
Organizer
- Holger Frauenrath
Contact
- Holger Frauenrath