The development of emerging applications based on large-area flexible and wearable devices requires solution-processable thin-film electronics. Organic semiconductors can be processed in solution, but typically suffer from relatively low performance and insufficient stability in ambient conditions. Inorganic nanostructures, however, can be processed in solution while retaining the excellent electronic performance and structural stability of crystalline inorganic materials. In particular, a range of two-dimensional inorganic nanosheets can be dispersed in various solvents as stable colloidal inks. These nanosheets can be assembled into continuous thin films in which neighbouring sheets interact via van der Waals forces with few interfacial trapping states. The resulting tiled nanosheets, which we term two-dimensional van der Waals thin films, offer significant potential in thin-film electronics. Here we explore the development of van der Waals thin films and their use in high-performance large-area electronics. We examine the formulation of the nanosheet inks and their scalable assembly into van der Waals thin films and devices. We also consider their application in large-area wearable electronics and the challenges that exist in delivering practical devices.
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Reuss, R. H. et al. Macroelectronics: perspectives on technology and applications. Proc. IEEE 93, 1239–1256 (2005).
Reuss, R. H., Hopper, D. G. & Park, J.-G. Macroelectronics. MRS Bull. 31, 447–454 (2006).
Rogers, J. A. et al. Paper-like electronic displays: large-area rubber-stamped plastic sheets of electronics and microencapsulated electrophoretic inks. Proc. Natl Acad. Sci. USA 98, 4835–4840 (2001).
Duan, X. et al. High-performance thin-film transistors using semiconductor nanowires and nanoribbons. Nature 425, 274–278 (2003). This paper reported the early effort in thin-film electronics based on assembled 1D semiconductor nanowire thin films.
Kelly, A. G. et al. All-printed thin-film transistors from networks of liquid-exfoliated nanosheets. Science 356, 69–73 (2017).
Arias, A. C., MacKenzie, J. D., McCulloch, I., Rivnay, J. & Salleo, A. Materials and applications for large area electronics: solution-based approaches. Chem. Rev. 110, 3–24 (2010).
Yuan, Y. et al. Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method. Nat. Commun. 5, 3005 (2014).
Newman, C. R. et al. Introduction to organic thin film transistors and design of n-channel organic semiconductors. Chem. Mater. 16, 4436–4451 (2004).
Sun, Y. & Rogers, J. A. Inorganic semiconductors for flexible electronics. Adv. Mater. 19, 1897–1916 (2007).
Ridley, B. A., Nivi, B. & Jacobson, J. M. All-inorganic field effect transistors fabricated by printing. Science 286, 746–749 (1999). This paper reported the early effort in thin-film electronics constructed from 0D quantum dots.
Choi, J.-H. et al. Exploiting the colloidal nanocrystal library to construct electronic devices. Science 352, 205–208 (2016). This paper presented state-of-the-art thin-film electronics on a flexible substrate constructed from 0D quantum dots.
Mitzi, D. B. Solution processing of chalcogenide semiconductors via dimensional reduction. Adv. Mater. 21, 3141–3158 (2009).
Lin, Z. et al. Cosolvent approach for solution-processable electronic thin films. ACS Nano 9, 4398–4405 (2015).
Talapin, D. V., Lee, J.-S., Kovalenko, M. V. & Shevchenko, E. V. Prospects of colloidal nanocrystals for electronic and optoelectronic applications. Chem. Rev. 110, 389–458 (2010).
Kovalenko, M. V., Scheele, M. & Talapin, D. V. Colloidal nanocrystals with molecular metal chalcogenide surface ligands. Science 324, 1417–1420 (2009).
Talapin, D. V. & Murray, C. B. PbSe nanocrystal solids for n-and p-channel thin film field-effect transistors. Science 310, 86–89 (2005).
Xu, F. & Zhu, Y. Highly conductive and stretchable silver nanowire conductors. Adv. Mater. 24, 5117–5122 (2012).
Hu, L., Kim, H. S., Lee, J.-Y., Peumans, P. & Cui, Y. Scalable coating and properties of transparent, flexible, silver nanowire electrodes. ACS Nano 4, 2955–2963 (2010).
Jin, S. et al. Scalable interconnection and integration of nanowire devices without registration. Nano Lett. 4, 915–919 (2004).
Snow, E. S., Novak, J. P., Campbell, P. M. & Park, D. Random networks of carbon nanotubes as an electronic material. Appl. Phys. Lett. 82, 2145–2147 (2003). This paper presented the early exploration of nanotube networks for thin-film electronics.
Cao, Q. et al. Medium-scale carbon nanotube thin-film integrated circuits on flexible plastic substrates. Nature 454, 495–500 (2008).
Xiang, L. et al. Low-power carbon nanotube-based integrated circuits that can be transferred to biological surfaces. Nat. Electron. 1, 237–245 (2018).
Geim, A. K. & Grigorieva, I. V. Van der Waals heterostructures. Nature 499, 419–425 (2013).
Lin, Z. et al. Solution processable colloidal nanoplates as building blocks for high-performance electronic thin films on flexible substrates. Nano Lett. 14, 6547–6553 (2014). This paper presented the concept of assembling van der Waals thin films from solution-processable 2D nanostructures.
Lin, Z. et al. Solution-processable 2D semiconductors for high-performance large-area electronics. Nature 562, 254–258 (2018). This paper demonstrated the formulation of high-quality phase-pure semiconducting MoS 2 ink solution and the assembly of van der Waals thin films for integrated logic circuits.
Israelachvili, J. N. Intermolecular and Surface Forces (Academic Press, Elsevier, 2011).
Jung, W. et al. Colloidal synthesis of single-layer MSe2 (M = Mo, W) nanosheets via anisotropic solution-phase growth approach. J. Am. Chem. Soc. 137, 7266–7269 (2015).
Sokolikova, M. S., Sherrell, P. C., Palczynski, P., Bemmer, V. L. & Mattevi, C. Direct solution-phase synthesis of 1T’ WSe2 nanosheets. Nat. Commun. 10, 712 (2019).
Mahler, B., Hoepfner, V., Liao, K. & Ozin, G. A. Colloidal synthesis of 1T-WS2 and 2H-WS2 nanosheets: applications for photocatalytic hydrogen evolution. J. Am. Chem. Soc. 136, 14121–14127 (2014).
Sun, Y., Fujisawa, K., Terrones, M. & Schaak, R. E. Solution synthesis of few-layer WTe2 and MoxW1−xTe2 nanostructures. J. Mater. Chem. C. 5, 11317–11323 (2017).
Boles, M. A., Ling, D., Hyeon, T. & Talapin, D. V. The surface science of nanocrystals. Nat. Mater. 15, 141–153 (2016).
Amani, M. et al. Solution-synthesized high-mobility tellurium nanoflakes for short-wave infrared photodetectors. ACS Nano 12, 7253–7263 (2018).
Wang, Y. et al. Field-effect transistors made from solution-grown two-dimensional tellurene. Nat. Electron. 1, 228–236 (2018).
Paton, K. R. et al. Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids. Nat. Mater. 13, 624–630 (2014).
Coleman, J. N. et al. Two-dimensional nanosheets produced by liquid exfoliation of layered materials. Science 331, 568–571 (2011). This paper presented the liquid-phase exfoliation of diverse 2D crystals into solution-processable ink materials.
Coleman, J. N. Liquid exfoliation of defect-free graphene. Acc. Chem. Res. 46, 14–22 (2012).
Pan, K. et al. Sustainable production of highly conductive multilayer graphene ink for wireless connectivity and IoT applications. Nat. Commun. 9, 5197 (2018).
Worsley, R. et al. All-2D material inkjet-printed capacitors: toward fully printed integrated circuits. ACS Nano 13, 54–60 (2019).
Backes, C. et al. Production of highly monolayer enriched dispersions of liquid-exfoliated nanosheets by liquid cascade centrifugation. ACS Nano 10, 1589–1601 (2016).
Zeng, Z. et al. Single‐layer semiconducting nanosheets: high‐yield preparation and device fabrication. Angew. Chem. Int. Ed. 50, 11093–11097 (2011). This paper reported the early effort in lithium-intercalation exfoliation of MoS 2 nanosheets in solution and demonstration of electronic applications.
Kappera, R. et al. Phase-engineered low-resistance contacts for ultrathin MoS2 transistors. Nat. Mater. 13, 1128–1134 (2014).
Wang, L., Xu, Z., Wang, W. & Bai, X. Atomic mechanism of dynamic electrochemical lithiation processes of MoS2 nanosheets. J. Am. Chem. Soc. 136, 6693–6697 (2014).
Zheng, J. et al. High yield exfoliation of two-dimensional chalcogenides using sodium naphthalenide. Nat. Commun. 5, 2995 (2014).
Fan, X. et al. Fast and efficient preparation of exfoliated 2H MoS2 nanosheets by sonication-assisted lithium intercalation and infrared laser-induced 1T to 2H phase reversion. Nano Lett. 15, 5956–5960 (2015).
Eda, G. et al. Photoluminescence from chemically exfoliated MoS2. Nano Lett. 11, 5111–5116 (2011).
Park, S., Vosguerichian, M. & Bao, Z. A review of fabrication and applications of carbon nanotube film-based flexible electronics. Nanoscale 5, 1727–1752 (2013).
Fan, Z. et al. Toward the development of printable nanowire electronics and sensors. Adv. Mater. 21, 3730–3743 (2009).
Kagan, C. R. & Andry, P. Thin-film Transistors (CRC Press, 2003).
Zhao, Y. et al. High‐electron‐mobility and air‐stable 2D layered PtSe2 FETs. Adv. Mater. 29, 1604230 (2017).
Bandurin, D. A. et al. High electron mobility, quantum Hall effect and anomalous optical response in atomically thin InSe. Nat. Nanotechnol. 12, 223–227 (2017).
Li, L. et al. Black phosphorus field-effect transistors. Nat. Nanotechnol. 9, 372–377 (2014).
Yang, S. et al. A delamination strategy for thinly layered defect‐free high‐mobility black phosphorus flakes. Angew. Chem. Int. Ed. 130, 4767–4771 (2018).
Liu, Y. et al. Toward barrier free contact to molybdenum disulfide using graphene electrodes. Nano Lett. 15, 3030–3034 (2015).
Yang, S. et al. Ultrafast delamination of graphite into high‐quality graphene using alternating currents. Angew. Chem. Int. Ed. 56, 6669–6675 (2017).
Zhang, Z. et al. Van der Waals epitaxial growth of 2D metallic vanadium diselenide single crystals and their extra‐high electrical conductivity. Adv. Mater. 29, 1702359 (2017).
Ma, H. et al. Thickness-tunable synthesis of ultrathin type-II Dirac semimetal PtTe2 single crystals and their thickness-dependent electronic properties. Nano Lett. 18, 3523–3529 (2018).
Zhang, C. et al. Transparent, flexible, and conductive 2D titanium carbide (MXene) films with high volumetric capacitance. Adv. Mater. 29, 1702678 (2017).
Zhu, J. et al. Solution-processed dielectrics based on thickness-sorted two-dimensional hexagonal boron nitride nanosheets. Nano Lett. 15, 7029–7036 (2015). This paper reported the assembly of low-leakage thin-film dielectrics from solution-processed 2D BN nanosheets.
Osada, M. et al. High‐κ dielectric nanofilms fabricated from titania nanosheets. Adv. Mater. 18, 1023–1027 (2006).
Matsuba, K. et al. Neat monolayer tiling of molecularly thin two-dimensional materials in 1 min. Sci. Adv. 3, e1700414 (2017).
Richardson, J. J., Björnmalm, M. & Caruso, F. Technology-driven layer-by-layer assembly of nanofilms. Science 348, aaa2491 (2015).
Cassagneau, T., Guérin, F. & Fendler, J. H. Preparation and characterization of ultrathin films layer-by-layer self-assembled from graphite oxide nanoplatelets and polymers. Langmuir 16, 7318–7324 (2000).
Sasaki, T. et al. Layer-by-layer assembly of titania nanosheet/polycation composite films. Chem. Mater. 13, 4661–4667 (2001).
Li, L. et al. Layer-by-layer assembly and spontaneous flocculation of oppositely charged oxide and hydroxide nanosheets into inorganic sandwich layered materials. J. Am. Chem. Soc. 129, 8000–8007 (2007).
Li, X. et al. Highly conducting graphene sheets and Langmuir–Blodgett films. Nat. Nanotechnol. 3, 538–542 (2008).
Taguchi, Y. et al. Fabrication of hybrid layered films of MoS2 and an amphiphilic ammonium cation using the Langmuir–Blodgett technique. Langmuir 14, 6550–6555 (1998).
Yu, X., Prévot, M. S., Guijarro, N. & Sivula, K. Self-assembled 2D WSe2 thin films for photoelectrochemical hydrogen production. Nat. Commun. 6, 7596 (2015).
Kaur, H. et al. Large area fabrication of semiconducting phosphorene by. Langmuir–Blodgett Assem. Sci. Rep. 6, 34095 (2016).
Osada, M. et al. Robust high-κ response in molecularly thin perovskite nanosheets. ACS Nano 4, 5225–5232 (2010).
Li, D., Müller, M. B., Gilje, S., Kaner, R. B. & Wallace, G. G. Processable aqueous dispersions of graphene nanosheets. Nat. Nanotechnol. 3, 101–105 (2008).
Borini, S. et al. Ultrafast graphene oxide humidity sensors. ACS Nano 7, 11166–11173 (2013).
Moon, I. K. et al. 2D graphene oxide nanosheets as an adhesive over-coating layer for flexible transparent conductive electrodes. Sci. Rep. 3, 1112 (2013).
Hantanasirisakul, K. et al. Fabrication of Ti3C2Tx MXene transparent thin films with tunable optoelectronic properties. Adv. Electron. Mater. 2, 1600050 (2016).
Zhong, J. et al. Efficient and scalable synthesis of highly aligned and compact two-dimensional nanosheet films with record performances. Nat. Commun. 9, 3484 (2018).
Min, K. et al. A facile route to fabricate stable reduced graphene oxide dispersions in various media and their transparent conductive thin films. J. Colloid Interface Sci. 383, 36–42 (2012).
Carey, T. et al. Fully inkjet-printed two-dimensional material field-effect heterojunctions for wearable and textile electronics. Nat. Commun. 8, 1202 (2017).
Casiraghi, C. et al. Inkjet printed 2D-crystal based strain gauges on paper. Carbon 129, 462–467 (2018).
McManus, D. et al. Water-based and biocompatible 2D crystal inks for all-inkjet-printed heterostructures. Nat. Nanotechnol. 12, 343–350 (2017). This paper demonstrated inkjet-printable 2D crystals for the construction of multilayer heterostructures and logic memory devices.
Bariya, M. et al. Roll-to-roll gravure printed electrochemical sensors for wearable and medical devices. ACS Nano 12, 6978–6987 (2018).
Kim, S. J., Choi, K., Lee, B., Kim, Y. & Hong, B. H. Materials for flexible, stretchable electronics: graphene and 2D materials. Annu. Rev. Mater. Res. 45, 63–84 (2015).
He, Q. et al. Fabrication of flexible MoS2 thin‐film transistor arrays for practical gas‐sensing applications. Small 8, 2994–2999 (2012).
Fiori, G. et al. Electronics based on two-dimensional materials. Nat. Nanotechnol. 9, 768–779 (2014).
Zhu, W. et al. Flexible black phosphorus ambipolar transistors, circuits and AM demodulator. Nano Lett. 15, 1883–1890 (2015).
González, R. I. et al. Bending energy of 2D materials: graphene, MoS2 and imogolite. RSC Adv. 8, 4577–4583 (2018).
Yan, H. et al. A high-mobility electron-transporting polymer for printed transistors. Nature 457, 679–686 (2009).
Oh, J. Y. et al. Intrinsically stretchable and healable semiconducting polymer for organic transistors. Nature 539, 411–415 (2016).
Li, J. et al. A stable solution-processed polymer semiconductor with record high-mobility for printed transistors. Sci. Rep. 2, 754 (2012).
Fix, W., Ullmann, A., Ficker, J. & Clemens, W. Fast polymer integrated circuits. Appl. Phys. Lett. 81, 1735–1737 (2002).
Drury, C., Mutsaers, C., Hart, C., Matters, M. & De Leeuw, D. Low-cost all-polymer integrated circuits. Appl. Phys. Lett. 73, 108–110 (1998).
Tang, J. et al. Flexible CMOS integrated circuits based on carbon nanotubes with sub-10 ns stage delays. Nat. Electron. 1, 191–196 (2018).
Shao, Y. et al. Graphene-based materials for flexible supercapacitors. Chem. Soc. Rev. 44, 3639–3665 (2015).
Paterson, A. F. & Anthopoulos, T. D. Enabling thin-film transistor technologies and the device metrics that matter. Nat. Commun. 9, 5264 (2018).
X.D. acknowledges support from the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering through award DE-SC0018828. Y.H. acknowledges financial support from National Science Foundation grant EFRI-1433541.
The authors declare no competing interests.
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