The role of surface passivation for efficient and photostable PbS quantum dot solar cells

  • Nature Energy 1, Article number: 16035 (2016)
  • doi:10.1038/nenergy.2016.35
  • Download Citation
Published online:


For any emerging photovoltaic technology to become commercially relevant, both its power conversion efficiency and photostability are key parameters to be fulfilled. Colloidal quantum dot solar cells are a solution-processed, low-cost technology that has reached an efficiency of about 9% by judiciously controlling the surface of the quantum dots to enable surface passivation and tune energy levels. However, the role of the quantum dot surface on the stability of these solar cells has remained elusive. Here we report on highly efficient and photostable quantum dot solar cells with efficiencies of 9.6% (and independently certificated values of 8.7%). As a result of optimized surface passivation and the suppression of hydroxyl ligands—which are found to be detrimental for both efficiency and photostability—the efficiency remains within 80% of its initial value after 1,000 h of continuous illumination at AM1.5G. Our findings provide insights into the role of the quantum dot surface in both the stability and efficiency of quantum dot solar cells.

  • Subscribe to Nature Energy for full access:



Additional access options:

Already a subscriber?  Log in  now or  Register  for online access.


  1. 1.

    ,  & Hybrid nanorod-polymer solar cells. Science 295, 2425–2427 (2002).

  2. 2.

    et al. Solution-processed PbS quantum dot infrared photodetectors and photovoltaics. Nature Mater. 4, 138–142 (2005).

  3. 3.

    et al. Colloidal-quantum-dot photovoltaics using atomic-ligand passivation. Nature Mater. 10, 765–771 (2011).

  4. 4.

    et al. Hybrid passivated colloidal quantum dot solids. Nature Nanotech. 7, 577–582 (2012).

  5. 5.

    , ,  & Improved performance and stability in quantum dot solar cells through band alignment engineering. Nature Mater. 13, 796–801 (2014).

  6. 6.

    et al. Air-stable n-type colloidal quantum dot solids. Nature Mater. 13, 822–828 (2014).

  7. 7.

    , , ,  & Solar cells based on junctions between colloidal PbSe nanocrystals and thin ZnO films. ACS Nano 3, 3638–3648 (2009).

  8. 8.

    et al. Depleted-heterojunction colloidal quantum dot solar cells. ACS Nano 4, 3374–3380 (2010).

  9. 9.

    et al. Solution-processed inorganic bulk nano-heterojunctions and their application to solar cells. Nature Photon. 6, 529–534 (2012).

  10. 10.

    et al. Remote trap passivation in colloidal quantum dot bulk nano-heterojunctions and its effect in solution-processed solar cells. Adv. Mater. 26, 4741–4747 (2014).

  11. 11.

    et al. Stability assessment on a 3% bilayer PbS/ZnO quantum dot heterojunction solar cell. Adv. Mater. 22, 3704–3707 (2010).

  12. 12.

    et al. Energy level modification in lead sulfide quantum dot thin films through ligand exchange. ACS Nano 8, 5863–5872 (2014).

  13. 13.

     & Charge trapping in bright and dark states of coupled PbS quantum dot films. ACS Nano 6, 3292–3303 (2012).

  14. 14.

    et al. Dependence of carrier mobility on nanocrystal size and ligand length in PbSe nanocrystal solids. Nano Lett. 10, 1960–1969 (2010).

  15. 15.

    et al. Size-tunable, bright, and stable PbS quantum dots: a surface chemistry study. ACS Nano 5, 2004–2012 (2011).

  16. 16.

    et al. Quantum dot photovoltaics in the extreme quantum confinement regime: the surface-chemical origins of exceptional air- and light-stability. ACS Nano 4, 869–878 (2010).

  17. 17.

    ,  & Efficient, air-stable colloidal quantum dot solar cells encapsulated using atomic layer deposition of a nanolaminate barrier. Appl. Phys. Lett. 103, 263905 (2013).

  18. 18.

    , ,  & PbS colloidal quantum dot/ZnO-based bulk heterojunction solar cells with high stability under continuous light soaking. Phys. Status Solidi RRL 8, 961–965 (2014).

  19. 19.

    et al. Schotty solar cells based on colloidal nanocrystal films. Nano Lett. 8, 3488–3492 (2008).

  20. 20.

    et al. Efficient, stable infrared photovoltaics based on solution-cast colloidal quantum dots. ACS Nano 2, 833–840 (2008).

  21. 21.

    et al. Hydroxylation of the surface of PbS nanocrystals passivated with oleic acid. Science 344, 1380–1384 (2014).

  22. 22.

    ,  & X-ray photoelectron spectroscopy sulfur 2p study of organic thiol and disulfide binding interactions with gold surfaces. Langmuir 12, 5083–5086 (1996).

  23. 23.

    et al. Low-temperature annealed PbS quantum dot films for scalable and flexible ambipolar thin-film-transistors and circuits. J. Mater. Chem. C 2, 10305–10311 (2014).

  24. 24.

    et al. Dissociation and oxidation of methanol on Cu(110). Surf. Sci. 507, 845–850 (2002).

  25. 25.

    et al. Structural, optical, and electrical properties of self-assembled films of PbSe nanocrystals treated with 1,2-ethanedithiol. ACS Nano 2, 271–280 (2008).

  26. 26.

    et al. High charge-carrier mobility enables exploitation of carrier multiplication in quantum-dot films. Nature Commun. 4, 2360 (2013).

  27. 27.

    et al. Epitaxially connected PbSe quantum-dot films: controlled neck formation and optoelectronic properties. ACS Nano 8, 11499–11511 (2014).

  28. 28.

    et al. Improvement in carrier transport properties by mild thermal annealing of PbS quantum dot solar cells. Appl. Phys. Lett. 102, 043506 (2013).

  29. 29.

    et al. Light-induced degradation of the active layer of polymer-based solar cells. Polym. Degrad. Stab. 95, 278–284 (2010).

  30. 30.

    et al. Photochemical stability of high efficiency PTB7:PC70BM solar cell blends. J. Mater. Chem. A 2, 20189–20195 (2014).

  31. 31.

    ,  & Oxidation of hydrogenated Si(111) by a radical propagation mechanism. J. Phys. Chem. C 116, 24607–24615 (2012).

  32. 32.

     & Stabilization of Si photoanodes in aqueous electrolytes through surface alkylation. J. Phys. Chem. B 102, 4058–4060 (1998).

  33. 33.

    , , ,  & Hybrid zinc oxide conjugated polymer bulk heterojunction solar cells. J. Phys. Chem. B 109, 9505–9516 (2005).

  34. 34.

    , , ,  & The effect of Al2O3 barrier layers in TiO2/Dye/CuSCN photovoltaic cells explored by recombination and DOS characterization using transient photovoltage measurements. J. Phys. Chem. B 109, 4616–4623 (2005).

  35. 35.

    et al. Experimental determination of the rate law for charge carrier decay in a polythiophene: fullerene solar cell. Appl. Phys. Lett. 92, 093311 (2008).

Download references


The research leading to these results has received funding from Fundació Privada Cellex, and European Community’s Seventh Framework Programme (FP7-ENERGY.2012.10.2.1) under grant agreement 308997. We also acknowledge financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) and the ‘Fondo Europeo de Desarrollo Regional’ (FEDER) through grant MAT2014-56210-R, as well as the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0522). This work was also supported by AGAUR under the SGR grant (2014SGR1548). The authors thank N. C. Miller for optical model simulation and measurement assistance, H. Mäckel for providing the TPC/TPV set-up and Q. Liu for measurement assistance.

Author information

Author notes

    • Yiming Cao
    •  & Alexandros Stavrinadis

    These authors contributed equally to this work.


  1. ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain

    • Yiming Cao
    • , Alexandros Stavrinadis
    • , Tania Lasanta
    • , David So
    •  & Gerasimos Konstantatos
  2. ICREA-Institució Catalana de Recerca i Estudis Avançats, Lluis Companys 23, 08010 Barcelona, Spain

    • Gerasimos Konstantatos


  1. Search for Yiming Cao in:

  2. Search for Alexandros Stavrinadis in:

  3. Search for Tania Lasanta in:

  4. Search for David So in:

  5. Search for Gerasimos Konstantatos in:


G.K. supervised the study. Y.C. and G.K. designed and directed this study and co-wrote the manuscript with feedback from all co-authors. Y.C. fabricated solar cells, characterized their photovoltaic performance, performed ageing tests under AM1.5G illumination, and analysed the XPS and UPS of QD solids. A.S. performed FIB imaging, synthesized colloidal PbS QDs, fabricated and characterized solar cells, and analysed the XPS results. T.L. synthesized colloidal PbS QDs. D.S. performed FET measurements.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Gerasimos Konstantatos.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    Supplementary Figures 1–20, Supplementary Tables 1–7, Supplementary References.