Low-temperature solution-processed graphene oxide derivative hole transport layer for organic solar cells

A Mo6+ cation modified graphene oxide (GO) derivative of GO-Mo was synthesized by a low-temperature solution method with different amounts of ammonium heptamolybdate (Mo-precursor) added into the GO solutions. The GO-Mo products were characterized through Raman microspectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy measurements and their photoelectric properties were systematically investigated. Organic bulk heterojunction solar cells with GO-Mo as the hole transport layer (HTL) were fabricated and their performance as a function of the number of GO-Mo layers was also studied. The performance of these devices was much better than that of the device with GO as the HTL. The best performance of the device with a power conversion efficiency of 2.61%, an open-circuit voltage of 0.59 V and a short-circuit current density of 9.02 mA cm−2 were obtained. Finally, the effect of the Mo-precursor weight in the GO solution on the device performance was discussed.