Charge Photogeneration in Organic Photovoltaics: Role of Hot versus Cold Charge‐Transfer Excitons
Abstract
The role of excess excitation energy on long‐range charge separation in organic donor/acceptor bulk heterojunctions (BHJs) continues to be unclear. While ultrafast spectroscopy results argue for efficient charge separation through high‐energy charge‐transfer (CT) states within the first picosecond (ps) of excitation, charge collection measurements suggest excess photon energy does not increase the current density in BHJ devices. Here, the population dynamics of charge‐separated polarons upon excitation of high‐energy polymer states and low‐energy interfacial CT states in two polymer/fullerene blends from ps to nanosecond time scales are studied. It is observed that the charge‐separation dynamics do not show significant dependence on excitation energy. These results confirm that excess exciton energy is not necessary for the effective generation of charges.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Oct 26, 2015
- Source ID
- 10.1002/aenm.201501032
Entities
People
- Bhoj R. Gautam
- Erik Klump
- Evgeny Danilov
- Franky So
- Harald Ade
- Iordania Constantinou
- Kenan Gundogdu
- Liang Yan
- Robert Younts
- Wei You
- Wentao Li
Organizations
- North Carolina State University
- Office of Naval Research
- University of North Carolina at Chapel Hill