Paul Blom 2013-2014 Seminar Series
January 22, 2014
In solar cells, free charge carriers can recombine both via bimolecular (Langevin) and trap-assisted recombination (Shockley-Read-Hall). Trap-assisted recombination of electrons and holes is governed by capture coefficients that are thermally activated with an identical activation energy as measured for the hole mobility μp. To elucidate which recombination mechanism is dominant in organic solar cells, we investigated Charge-transfer (CT) state electroluminescence in several polymer:fullerene bulk heterojunction solar cells. The ideality factor of the electroluminescence reveals that the CT emission in polymer:fullerene solar cells originates from free-carrier bimolecular recombination at the donor-acceptor interface, rather than a charge trap-mediated process. These results are in agreement with measurements of the illumination-intensity dependence of the open-circuit voltage.
Post time: Jul-12-2017