|
Abstract
|
A combination of reduced graphene oxide (rGO) nanosheets grafted with regioregular poly(3-hexylthiophene)
(P3HT) (rGO-g-P3HT) and P3HT-b-polystyrene (PS) block copolymers was utilized to modify the morphology of
P3HT:[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) active layers in photovoltaic devices. Efficiencies greater than
6% were acquired after a mild thermal annealing. To this end, the assembling of P3HT homopolymers and P3HT-b-PS
block copolymers onto rGO-g-P3HT nanosheets was investigated, showing that the copolymers were assembled from the
P3HT side onto the rGO-g-P3HT nanosheets. Assembling of P3HT-b-PS block copolymers onto the rGO-g-P3HT nanosheets
developed the net hole and electron highways for charge transport, thereby in addition to photoluminescence quenching the charge mobility (�h and �e) values increased considerably. The best charge mobilities were acquired for the
P3HT
50000:PC71BM:rGO-g-P3HT50000:P3HT7000-b-PS1000 system (�h = 1.9 × 10−5 cm2 V–1 s–1 and �e = 0.8 × 10−4 cm2 V–1 s–1).
Thermal annealing conducted at 120 ∘C also further increased the hole and electron mobilities to 9.8 × 10−4 and 2.7 × 10−3 cm2
V–1 s–1, respectively. The thermal annealing acted as a driving force for better assembly of the P3HT-b-PS copolymers onto
the rGO-g-P3HT nanosheets. This phenomenon improved the short circuit current density, fill factor, open circuit voltage and
power conversion efficiency parameters from 11.13 mA cm−2, 0.63 V, 62% and 4.35% to 12.98 mA cm−2, 0.69 V, 68% and 6.09%,
respectively.
|