Complementary n‐Type and p‐Type Graphene Films for High Power Factor Thermoelectric Generators

Abstract

Solution-phase exfoliated graphene has always been an attractive material for flexible thermoelectric applications, but traditional oxidative routes suffer from poor flake quality and a lack of quality doping techniques to make complementary n-type and p-type films. Here, it is demonstrated that by changing the adsorbed surfactant during the intercalation-exfoliation process (polyvinylpyrrolidone for n-type, pyrenebutyric acid for p-type), both extremely high electrical conductivity (3010 and 2330 S cm −1 ) and high Seebeck coefficients (53.1 and −45.5 µV K −1 ) can be achieved. The result is that both of these films show remarkable power factors, over 600 µW m −1 K −2 at room temperature, which is over an order of magnitude better than that in previous works demonstrating complementary n-type and p-type graphene thermoelectric films. Based on these films, a full all-graphene thermoelectric device is constructed as a proof of concept, where a peak power of 5.0 nW is recorded at a temperature difference of 50 K.

Large-Area Thermal Distribution Sensor Based on Multilayer Graphene Ink

“…A likely reason is that the absence of other than atmospheric dopants results in a lower charge carrier concentration, but at the same time, there are no large dopant molecules contributing to carrier scattering, which promotes higher carrier mobility. While the resistivities observed in this work range from 48 to 87 µΩ m, in sound agreement with similarly fabricated films [ 20 ], the values are an order of magnitude greater compared to those reported by Novak et al [ 16 ], likely due to smaller flake size and, thus, shorter carrier mean free path and enhanced interface scattering. As a further comparison, the mobility values of inkjet-printed n-type graphene films have been reported to possess electron mobilities ranging from 8.9 to 23.9 cm 2 V −1 s −1 as a function of increasing film thickness [ 50 ], agreeing well with the results reported here.…”

“…When compared to results from previous studies on p-type liquid-phase exfoliated graphene films, the electronic properties agree well with atmospherically doped films [ 20 ]. However, in comparison to polymer-doped films, our results show a lower hole concentration but a larger carrier mobility [ 16 ]. A likely reason is that the absence of other than atmospheric dopants results in a lower charge carrier concentration, but at the same time, there are no large dopant molecules contributing to carrier scattering, which promotes higher carrier mobility.…”

“…Films of graphene can be fabricated in large area either by chemical vapor deposition (CVD) or via liquid-phase processes, thus fulfilling the physical size requirements associated with tactile user interfaces. Recently, solution-processed few-layer graphene has been reported to provide a thermoelectric response with Seebeck coefficient S > 80 μV K −1 [ 14 ] and power factor PF = S 2 σ > 600 μW m −1 K −2 [ 15 , 16 ], rendering it intriguing for thermal sensing applications as well.…”

“…Despite the favorable characteristics, thermoelectric applications exploiting graphene remain scarcely reported. Previous reports considering the utilization of graphene as an active material for thermoelectric devices include the exploitation of both CVD-grown and solution-processed graphene [ 16 , 17 , 18 , 19 , 20 ] often in combination with either carbon nanotubes (CNTs) or conductive polymers [ 15 , 21 , 22 , 23 , 24 , 25 ]. Nevertheless, only a few of the proposed approaches possess a large-area architecture suitable for detecting distributions in temperature [ 19 , 26 ].…”

Synthesis and applications of WO3 nanosheets: the importance of phase, stoichiometry, and aspect ratio

“…For ionic salts, this can be easily accomplished by heating in an inert environment to allow dissociation of the salt without formation of side products. This approach has been widely reported to generate graphene of higher aspect ratio than other approaches, [70][71][72] and is commonly adapted for other VDW materials such as WS 2 and MoS 2 . 73 Fig.…”