Introduction
Liquid exfoliation
Fig.2 (a) Reduced graphene oxide spray-coated on a 4-inch quartz wafer. Adapted from Ref. [66]. (b) Rod-coated room-temperature reduced graphene oxide transferred on a flexible PET substrate. Adapted from Ref. [69]. (c) Scheme for Langmuir-Blodgett method where a graphene film forms at the air-water-interface. The substrate is pulled upwards while the film is under steady compression. The film adheres to the substrate as it is pulled, and a monolayer transfer is achieved. Adapted from Ref. [41] |
Tab.1 Summary of liquid exfoliated graphene based transparent electrodes, where , and refer to sheet resistance, transmittance (at 550 nm) and figure of merit, respectively. Annealing column mentions whether high-temperature annealing is done and at what temperature. Exfoliation method explains which method is used and whether surfactants are used; if only GO is mentioned, then no agitation is used for exfoliation |
Rs/(Ω·sq−1) | T/% | annealing/°C | exfoliation method | Ref. | |
---|---|---|---|---|---|
100 | 90 | 35 | – | – | minimum industry requirment [70] |
22500 | 62 | 0.03 | 250 | surfactant+ sonication | [71] |
40000 | 78 | 0.036 | 400a) | GO+ sonication | [68] |
5100 | 42 | 0.069 | 250 | sonication | [35] |
6000 | 60 | 0.11 | 400a) | GO+ sonication | [64] |
6000 | 70 | 0.16 | – | surfactant+ sonication | [40] |
1500 | 44 | 0.25 | – | shear | [52] |
3200 | 70 | 0.30 | 600 | electrochemical | [58] |
4000 | 76 | 0.32 | 500 | surfactant+ sonication | [72] |
5000 | 80 | 0.32 | 800 | surfactant+ GO+ sonication | [65] |
1000 | 47 | 0.41 | 500 | surfactant+ sonication | [72] |
1680 | 65 | 0.46 | – | GO+ sonication | [69] |
4000 | 82 | 0.56 | 1100 | GO+ sonication | [68] |
2000 | 74 | 0.58 | 400+1100a) | GO+ sonication | [64] |
550 | 48 | 0.78 | 600 | electrochemical | [58] |
1700 | 75 | 0.72 | – | GO | [67] |
2200 | 84 | 0.94 | 1100 | GO+ sonication | [66] |
930 | 75 | 1.3 | 300 | intercalation | [41] |
668 | 80 | 2.39 | 350 | surfactant+ sonication | [50] |
1100 | 89 | 2.86 | 700 | GO | [67] |
440 | 76 | 2.9 | 400 | electrochemical | [55] |
600 | 86 | 4.01 | 400+1100 | intercalation+ GO | [15] |
778 | 90 | 4.5 | 1000 | surfactant+ sonication | [48] |
330 | 87 | 4.8 | 300 | electrochemical | [56] |
459 | 90 | 7.59 | 400+1100b) | intercalation+ GO | [15] |
260 | 85 | 8.6 | 350 | shear | [43] |
657 | 96 | 13.9 | 450 | electrochemical | [54] |
210a) | 96 | 43.5 | 450 | electrochemical | [54] |
Notes: a) Hydrazine vapor+ annealing. b) Chemical doping via HNO3 and SOCl2. |
Chemical vapor deposition
Fig.3 (a) Schematic picture of a horizontal quartz furnace where gases flow laterally over the substrate in a reaction zone surrounded by heating elements. (b) Simplified scheme of graphene growth in CVD. Hydrocarbons adsorb on the surface (1), dehydrogenate (2), nucleate and grow (3), diffuse to bulk if high carbon soluble substrate (4), diffuse out (5), and segregate (6). Adapted from Ref. [84] |
Fig.4 Defect healing scheme by Park et al., where gold nanoparticles are electroplated onto defected areas, increasing their conductivity. Adapted from Ref. [109]. (a) Schematic figure on where the gold nanoparticles coalesce after electroplating process. (b) Electroplating scheme of the gold nanoparticles |
Fig.5 (a) Schematic of electrical injection of nickel atoms as p-type dopant by Chae et al., made with an AlN buffer layer. Adapted from Ref. [143]. (b) Chlorine doping of graphene in ICP by Pham et al., with two metal meshes to confine low energy radicals and protect the graphene layer. Adapted from Ref. [16] |
Tab.2 Summary of different graphene based transparent electrodes, where Rs, T, and Rchange refer to sheet resistance, transmittance (at 550 nm unless otherwise specified), figure of merit and decrease of sheet resistance due to doping, respectively. Substrate refers to the substrate where Rs and T are measured on, if two substrates are given, then their corresponding measurements are given in brackets after the substrate |
Rs/(Ω·sq−1) | T/% | Rchange/% | substrate | dopant (n/p) | Ref. | ||
---|---|---|---|---|---|---|---|
100 | 90 | 35 | – | – | – | minimum industry requirement [70] | |
3600 | 85.7 | 0.66 | – | flexible glass | – | [134]a) | |
1645 | 81 | 1.03 | – | quartz | – | [104] | |
1300 | 80 | 1.24 | – | quartz | – | [136]a) | |
1170 | 88 | 2.44 | – | PET | – | [103] | |
661 | 83.7 | 3.09 | – | glass | – | [135]a) | |
600 | 86 | 4.01 | 37 | SiO2 (Rs)/glass (T) | Au2S (p) | [139] | |
230 | 71 | 4.39 | – | PET | – | [145] | |
280 | 76 | 4.58 | – | quartz | – | [98] | |
700 | 90 | 4.98 | – | SiO2 (Rs)/glass (T) | – | [146] | |
350 | 83b) | 5.52 | – | – | pyridine (n)c) | [147] | |
445 | 87 | 5.87 | 47 | SiO2 (Rs)/PET (T) | AuCl3 (p) | [148] | |
820 | 93 | 6.22 | 14 | SiO2 (Rs)/glass (T) | Au(OH)3 (p) | [139] | |
1150 | 97 | 10.7 | – | glass | – | [149] | |
200 | 86.7 | 12.7 | 87 | EVA+PET | HNO3 (p) | [150] | |
530 | 95 | 13.7 | 44 | SiO2 (Rs)/glass (T) | AuBr3 (p) | [139] | |
350 | 93 | 14.6 | 52 | – | RhCl3 (p) | [140] | |
150 | 87 | 17.4 | 66 | SiO2 (Rs)/PET (T) | AuCl3 (p) | [148] | |
220 | 91 | 17.8 | 70 | – | AuCl3 (p) | [140] | |
500 | 96 | 18.3 | 32 | – | HNO3 (p) | [140] | |
118d) | 84.9 | 18.7 | 56 | glass | CsF (n) | [151] | |
129 | 88 | 22.1 | 70 | SiO2 (Rs)/sapphire (T) | TFSA (p)e) | [152] | |
550 | 97 | 22.3 | – | PVDFf) | – | [153] | |
380 | 96 | 24.1 | 42 | glass | hydrazine (n) | [141] | |
618 | 97.5 | 24.1 | – | glass | – | [137]a) | |
500 | 97.1 | 25.4 | – | quartz | – | [154] | |
299 | 95.7 | 28.4 | 62 | SiO2 (Rs)/quartz (T) | HNO3 (p) | [105] | |
81 | 85.6 | 29 | – | PESg) | – | [138]a) | |
300 | 96 | 30.5 | 68 | SiO2 (Rs)/glass (T) | AuCl3 (p) | [139] | |
216 | 95 | 33.6 | 70 | quartz | Ni (p)h) | [143] | |
367 | 97.3 | 37.3 | – | PET | – | [101] | |
215 | 96 | 42.5 | 44 | SiO2 (Rs)/glass (T) | Au NP (p) | [109] | |
320 | 98 | 58.0 | – | cellulose | – | [107] | |
50 | 89 | 62.8 | 76 | glass | hydrazine (n) | [141] | |
305 | 98.2 | 67.7 | 49 | PET | Cl plasma (p) | [16] | |
30d) | 90 | 116 | 25 | SiO2 (Rs)/PET (T) | HNO3 (p) | [106] | |
118i) | 97.3 | 116 | 80 | PET | Cl plasma (p) | [16] | |
115 | 97.5 | 135 | 50 | SiO2 (Rs)/PET (T) | HNO3 (p) | [106] | |
25 | 96.5 | 419 | 83 | parylene-C | HNO3 (p) | [108] |
Notes: a) PECVD directly on dielectric substrate. b) At 633 nm. c) In-situ doping. d) Stacked four-layer graphene. e) Bis(trifluoromethanesulfonyl)amide. f) Polyvinylidene fluoride. g) Polyestersulfone. h) Doped via electrical injection. i) Stacked two-layer graphene |