Skip to main content Accessibility help

General method to synthesize ultrasmall metal oxide nanoparticle suspensions for hole contact layers in organic photovoltaic devices

  • Yun-Ju Lee (a1), Jian Wang (a1), Julia W. P. Hsu (a1) and Diego Barrera (a2)


Solution-processed hole contact layers (HCLs) of metal oxide nanoparticle (NP) films improve performance of organic photovoltaics (OPVs), but have thus far required harsh post-deposition thermal or plasma treatments. Here, we describe a general method to synthesize suspensions of ultrasmall (1–2 nm) MoO3, WO3, NiOx, and CoOx NPs in n-butanol. Spin-coated metal oxide NP films with no post-deposition treatment exhibit high work function and ionization energy consistent with the oxidation states of the metal cations. Metal oxide NP HCLs demonstrate performance matching those of reference conventional and inverted OPVs containing PEDOT:PSS and evaporated MoO3.


Corresponding author

Address all correspondence to Yun-Ju Lee


Hide All
1.Greiner, M.T. and Lu, Z.-H.: Thin-film metal oxides in organic semiconductor devices: their electronic structures, work functions and interfaces. NPG Asia Mater. 5, e55 (2013).
2.Li, N., Baran, D., Forberich, K., Machui, F., Ameri, T., Turbiez, M., Carrasco-Orozco, M., Drees, M., Facchetti, A., Krebs, F.C., and Brabec, C.J.: Towards 15% energy conversion efficiency: a systematic study of the solution-processed organic tandem solar cells based on commercially available materials. Energy Environ. Sci. 6, 3407 (2013).
3.Søndergaard, R.R., Hösel, M., and Krebs, F.C.: Roll-to-roll fabrication of large area functional organic materials. J. Polym. Sci. B, Polym. Phys. 51, 16 (2013).
4.Steim, R., Kogler, F.R., and Brabec, C.J.: Interface materials for organic solar cells. J. Mater. Chem. 20, 2499 (2010).
5.Yip, H.-L. and Jen, A.K.Y.: Recent advances in solution-processed interfacial materials for efficient and stable polymer solar cells. Energy Environ. Sci. 5, 5994 (2012).
6.Zilberberg, K., Meyer, J., and Riedl, T.: Solution processed metal-oxides for organic electronic devices. J. Mater. Chem. C 1, 4796 (2013).
7.Steirer, K.X., Ndione, P.F., Widjonarko, N.E., Lloyd, M.T., Meyer, J., Ratcliff, E.L., Kahn, A., Armstrong, N.R., Curtis, C.J., Ginley, D.S., Berry, J.J., and Olson, D.C.: Enhanced efficiency in plastic solar cells via energy matched solution processed NiOx interlayers. Adv. Energy Mater. 1, 813 (2011).
8.Liu, F., Shao, S., Guo, X., Zhao, Y., and Xie, Z.: Efficient polymer photovoltaic cells using solution-processed MoO3 as anode buffer layer. Sol. Energy Mater. Sol. Cells 94, 842 (2010).
9.Chen, C.-P., Chen, Y.-D., and Chuang, S.-C.: High-performance and highly durable inverted organic photovoltaics embedding solution-processable vanadium oxides as an interfacial hole-transporting layer. Adv. Mater. 23, 3859 (2011).
10.Zilberberg, K., Gharbi, H., Behrendt, A., Trost, S., and Riedl, T.: Low-temperature, solution-processed MoOx for efficient and stable organic solar cells. ACS Appl. Mater. Interfaces 4, 1164 (2012).
11.Xie, F., Choy, W.C.H., Wang, C., Li, X., Zhang, S., and Hou, J.: Low-temperature solution-processed hydrogen molybdenum and vanadium bronzes for an efficient hole-transport layer in organic electronics. Adv. Mater. 25, 2051 (2013).
12.Zilberberg, K., Trost, S., Schmidt, H., and Riedl, T.: Solution processed vanadium pentoxide as charge extraction layer for organic solar cells. Adv. Energy Mater. 1, 377 (2011).
13.Steirer, K.X., Chesin, J.P., Widjonarko, N.E., Berry, J.J., Miedaner, A., Ginley, D.S., and Olson, D.C.: Solution deposited NiO thin-films as hole transport layers in organic photovoltaics. Org. Electron. 11, 1414 (2010).
14.Girotto, C., Voroshazi, E., Cheyns, D., Heremans, P., and Rand, B.P.: Solution-processed MoO3 thin films as a hole-injection layer for organic solar cells. ACS Appl. Mater. Interfaces 3, 3244 (2011).
15.Stubhan, T., Ameri, T., Salinas, M., Krantz, J., Machui, F., Halik, M., and Brabec, C.J.: High shunt resistance in polymer solar cells comprising a MoO3 hole extraction layer processed from nanoparticle suspension. Appl. Phys. Lett. 98, 253308 (2011).
16.Stubhan, T., Li, N., Luechinger, N.A., Halim, S.C., Matt, G.J., and Brabec, C.J.: High fill factor polymer solar cells incorporating a low temperature solution processed WO3 hole extraction layer. Adv. Energy Mater. 2, 1433 (2012).
17.Yang, T., Wang, M., Cao, Y., Huang, F., Huang, L., Peng, J., Gong, X., Cheng, S.Z.D., and Cao, Y.: Polymer solar cells with a low-temperature-annealed sol–gel-derived MoOx film as a hole extraction layer. Adv. Energy Mater. 2, 523 (2012).
18.Zilberberg, K., Trost, S., Meyer, J., Kahn, A., Behrendt, A., Lützenkirchen-Hecht, D., Frahm, R., and Riedl, T.: Inverted organic solar cells with sol–gel processed high work-function vanadium oxide hole-extraction layers. Adv. Funct. Mater. 21, 4776 (2011).
19.Lee, Y.-J., Yi, J., Gao, G.F., Koerner, H., Park, K., Wang, J., Luo, K., Vaia, R.A., and Hsu, J.W.P.: Low-temperature solution-processed molybdenum oxide nanoparticle hole transport layers for organic photovoltaic devices. Adv. Energy Mater. 2, 1193 (2012).
20.Huang, J.-H., Huang, T.-Y., Wei, H.-Y., Ho, K.-C., and Chu, C.-W.: Wet-milled transition metal oxide nanoparticles as buffer layers for bulk heterojunction solar cells. RSC Adv. 2, 7487 (2012).
21.Redel, E., Huai, C., Dag, Ö., Petrov, S., O'Brien, P.G., Helander, M.G., Mlynarski, J., and Ozin, G.A.: From bare metal powders to colloidally stable TCO dispersions and transparent nanoporous conducting metal oxide thin films. Small 8, 3806 (2012).
22.Meyer, J., Khalandovsky, R., Goerrn, P., and Kahn, A.: MoO3 films spin-coated from a nanoparticle suspension for efficient hole-injection in organic electronics. Adv. Mater. 23, 70 (2011).
23.Greiner, M.T., Chai, L., Helander, M.G., Tang, W.-M., and Lu, Z.-H.: Transition metal oxide work functions: the influence of cation oxidation state and oxygen vacancies. Adv. Funct. Mater. 22, 4557 (2012).
24.Meyer, J., Shu, A., Kroeger, M., and Kahn, A.: Effect of contamination on the electronic structure and hole-injection properties of MoO3/organic semiconductor interfaces. Appl. Phys. Lett. 96, 133308 (2010).
25.Ratcliff, E.L., Meyer, J., Steirer, K.X., Armstrong, N.R., Olson, D., and Kahn, A.: Energy level alignment in PCDTBT:PC70BM solar cells: solution processed NiOx for improved hole collection and efficiency. Org. Electron. 13, 744 (2012).
26.Biesinger, M.C., Payne, B.P., Grosvenor, A.P., Lau, L.W., Gerson, A.R., and Smart, R.S.: Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni. Appl. Surf. Sci. 257, 2717 (2011).
27.Ratcliff, E.L., Meyer, J., Steirer, K.X., Garcia, A., Berry, J.J., Ginley, D.S., Olson, D.C., Kahn, A., and Armstrong, N.R.: Evidence for near-surface NiOOH species in solution-processed NiOx selective interlayer materials: impact on energetics and the performance of polymer bulk heterojunction photovoltaics. Chem. Mater. 23, 4988 (2011).
28.Wagenpfahl, A., Rauh, D., Binder, M., Deibel, C., and Dyakonov, V.: S-shaped current-voltage characteristics of organic solar devices. Phys. Rev. B 82, 115306 (2010).
29.Park, S.H., Roy, A., Beaupre, S., Cho, S., Coates, N., Moon, J.S., Moses, D., Leclerc, M., Lee, K., and Heeger, A.J.: Bulk heterojunction solar cells with internal quantum efficiency approaching 100%. Nat. Photonics 3, 297 (2009).
30.Gao, W., Dickinson, L., Grozinger, C., Morin, F.G., and Reven, L.: Self-assembled monolayers of alkylphosphonic acids on metal oxides. Langmuir 12, 6429 (1996).

Related content

Powered by UNSILO
Type Description Title
Supplementary materials

Lee supplementary material S1
Lee supplementary material S1

 Word (493 KB)
493 KB

General method to synthesize ultrasmall metal oxide nanoparticle suspensions for hole contact layers in organic photovoltaic devices

  • Yun-Ju Lee (a1), Jian Wang (a1), Julia W. P. Hsu (a1) and Diego Barrera (a2)


Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.