Low-Temperature Combustion Synthesis of a Spinel NiCo2O4 Hole Transport Layer for Perovskite Photovoltaics

Ioannis T Papadas; Apostolos Ioakeimidis; Gerasimos S Armatas; Stelios A Choulis

doi:10.1002/advs.201701029

Low-Temperature Combustion Synthesis of a Spinel NiCo₂O₄ Hole Transport Layer for Perovskite Photovoltaics

Adv Sci (Weinh). 2018 Mar 3;5(5):1701029. doi: 10.1002/advs.201701029. eCollection 2018 May.

Authors

Ioannis T Papadas¹, Apostolos Ioakeimidis¹, Gerasimos S Armatas², Stelios A Choulis¹

Affiliations

¹ Molecular Electronics and Photonics Research Unit Department of Mechanical Engineering and Materials Science and Engineering Cyprus University of Technology Limassol 3041 Cyprus.
² Department of Materials Science and Technology University of Crete Heraklion 71003 Greece.

Abstract

The synthesis and characterization of low-temperature solution-processable monodispersed nickel cobaltite (NiCo₂O₄) nanoparticles (NPs) via a combustion synthesis is reported using tartaric acid as fuel and the performance as a hole transport layer (HTL) for perovskite solar cells (PVSCs) is demonstrated. NiCo₂O₄ is a p-type semiconductor consisting of environmentally friendly, abundant elements and higher conductivity compared to NiO. It is shown that the combustion synthesis of spinel NiCo₂O₄ using tartaric acid as fuel can be used to control the NPs size and provide smooth, compact, and homogeneous functional HTLs processed by blade coating. Study of PVSCs with different NiCo₂O₄ thickness as HTL reveals a difference on hole extraction efficiency, and for 15 nm, optimized thickness enhanced hole carrier collection is achieved. As a result, p-i-n structure of PVSCs with 15 nm NiCo₂O₄ HTLs shows reliable performance and power conversion efficiency values in the range of 15.5% with negligible hysteresis.

Keywords: NiCo2O4; combustion synthesis; hole transporting layers; perovskites solar cells; transparent conductive oxides.