Relaxation of photogenerated carriers in P3HT:PCBM organic blends.
The after-pulse time-resolved microwave conductivity (TRMC) decays observed in P3HT:PCBM blends display a dependence on time close to t(-beta), independent of excitation intensity, in the 10 ns-1 micros range. This is explained in terms of the relaxation of carriers in a Gaussian density of states (DOS). The model is based on a demarcation level that moves with time by thermal release and retrapping of initially trapped carriers. The model shows that when the disorder is large the after-pulse decay of the type t(-beta) is obtained, while at low disorder and large temperature the carrier distribution becomes independent of time. In the measurements different beta values were observed depending on the solvent used for spin-coating: 0.4-0.6 for chlorobenzene and 0.3-0.4 for toluene. The model was applied to extract the shape of the DOS from the TRMC decays, giving a dispersion parameter of about 120 meV for blends with high P3HT content.
Moehl
Thomas
T
Photovoltaic and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, 12071 Castelló, Spain.
Kytin
Vladimir G
VG
Bisquert
Juan
J
Kunst
Marinus
M
Bolink
Henk J
HJ
Garcia-Belmonte
Germà
G
D037741:Fullerenes / Q000737:chemistry*; D008872:Microwaves; D012993:Solar Energy; D013876:Thiophenes / Q000737:chemistry*; D013997:Time Factors
C539575:(6,6)-phenyl C61-butyric acid methyl ester; D037741:Fullerenes; D013876:Thiophenes; C507295:poly(3-hexylthiophene)