Microfluidic processing of ligand-engineered NiO nanoparticles for low-temperature hole-transporting layers in perovskite solar cells

Monika Michalska, Maciej Adam Surmiak, Fatemeh Maasoumi, Dimuthu C. Senevirathna, Paul Chantler, Hanchen Li, Bin Li, Tian Zhang, Xionfeng Lin, Hao Deng, Naresh Chandrasekaran, T. A.Nirmal Peiris, Kevin James Rietwyk, Anthony S.R. Chesman, Tuncay Alan, Doojin Vak, Udo Bach, Jacek J. Jasieniak

Research output: Contribution to journalArticleResearchpeer-review

11 Citations (Scopus)


Nickel oxide (NiO) is used as a hole-transporting layer (HTL) in perovskite solar cells (PSCs) because of its high optical transmittance, intrinsic p-type doping, and suitable valence band energy level. However, fabricating high-quality NiO films typically requires high-temperature annealing, which limits their applicability for low-temperature, printable PSCs. Herein, the need for such postprocessing steps is circumvented by coupling 4-hydroxybenzoic acid (HBA) or trimethyloxonium tetrafluoroborate (Me3OBF4) ligand-modified NiO nanoparticles (NPs) with a Tesla-valve microfluidic mixer to deposit high-quality NiO films at a temperature <150 °C. The NP dispersions and the resulting thin films are thoroughly characterized using a combination of optical, structural, thermal, chemical, and electrical methods. While the optical and structural properties of the ligand-exchanged NiO NPs remain comparable with those possessing the native long-chained aliphatic ligands, the ligand-modified NiO thin films exhibit dramatic reductions in surface energy and an increase in hole mobilities. These are correlated with concomitant and significant enhancements in performance and stability factors of PSCs when the ligand-modified NiO NPs are used as HTL layers within p−i−n device architectures.

Original languageEnglish
Article number2100342
Number of pages13
JournalSolar RRL
Issue number8
Publication statusPublished - Aug 2021


  • hole-transporting layers
  • ligand exchanges
  • low temperatures
  • nickel oxide
  • perovskite solar cells

Cite this