NiO/Graphene Composite for Enhanced Charge Separation and Collection in p-Type Dye Sensitized Solar Cell

Abstract

A p-type semiconductor photoelectrode in dye sensitized solar cells (DSCs) has a large optical band gap and high ionization potential but suffers from its intrinsically low hole transfer rate, thus resulting in much poorer performance than n-DSCs. Nickel oxide (NiO)/graphene composite is synthesized to offer a larger surface area and higher conductivity than the pristine NiO film. The novel composite as a photoelectrode in p-DSCs demonstrates increment of both short-circuit photocurrent and open-circuit photovoltage, leading to 2 times increase of power conversion efficiency. Electrochemical impedance spectroscopy and open-circuit voltage decay measurements indicate that the charge recombination of the composite-based p-DSCs is significantly suppressed due to enhanced hole transport by the presence of graphene, thus achieving an efficient electron–hole pair charge separation and collection in the composite film electrode for performance-improved NiO-based devices. The proposed mechanism provides physical insight into the enhancement process in p-DSCs.

Exceeding the limit of plasmonic light trapping in textured screen-printed solar cells using Al nanoparticles and wrinkle-like graphene sheets

“…12 In the absorption spectrum of the wrinkle-like graphene sheets (Figure 1c), a characteristic sp 2 absorption peak is located at approximately 280 nm. 21 Another peak is discernible at 840 nm, 22 unlike the planar graphene sheet ( Supplementary Fig. S1).…”

Graphene based metal and metal oxide nanocomposites: synthesis, properties and their applications

“…379 Apart from TiO 2 in group 4, HRG/NiO nanocomposites were used to fabricate photoelectrodes in high conductivity, it may serve as a shuttle to enhance electron transport and to suppress the recombination in n-type DSSCs. 382 The novel HRG/NiO composite has doubled its power conversion efficiency when applied as a photoelectrode in p-DSCs. Additionally, the composite photocathode (with an appropriate amount of graphene) offers faster hole transport and larger surface area than bare NiO films.…”

Recent advances in multifunctional nanocarbons used in dye-sensitized solar cells

“…5. [158][159][160][161][162][163][164][165][166][167] Intermolecular forces such as physisorption, electrostatic binding, and charge transfer govern the mutual interactions between metal oxides and graphene. To this date, three different procedures have been developed to prepare graphene doped composites.…”

“…158,159 Secondly, single and few layer graphene ake suspensions were prepared by chemical exfoliation under either oxidative or reductive conditions 160,161,165 or by ultrasonication with Naon as a stabilizer.…”

“…[158][159][160][161][162][163][164][165][166][167] Interesting is the observation by Li et al, who showed that V OC increases upon graphene doping from 73 to 105 mV in NiO-based devices. 165 This fact was ascribed to lower hole densities, since graphene traps and transports holes. Regardless of the type of electrode, the overall device efficiency was greatly improved.…”