Determining Out-of-Plane Hole Mobility in CuSCN via the Time-of-Flight Technique To Elucidate Its Function in Perovskite Solar Cells

Lokeshwari Mohan; Sinclair R Ratnasingham; Julianna Panidi; Matyas Daboczi; Ji-Seon Kim; Thomas D Anthopoulos; Joe Briscoe; Martyn A McLachlan; Theo Kreouzis

doi:10.1021/acsami.1c09750

Determining Out-of-Plane Hole Mobility in CuSCN via the Time-of-Flight Technique To Elucidate Its Function in Perovskite Solar Cells

ACS Appl Mater Interfaces. 2021 Aug 18;13(32):38499-38507. doi: 10.1021/acsami.1c09750. Epub 2021 Aug 7.

Authors

Affiliations

¹ Department of Materials and Centre for Processable Electronics, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, U.K.
² School of Engineering and Materials Science and Materials Research Institute, Queen Mary University of London, Mile End Road, London E1 4NS, U.K.
³ Department of Physics and Centre for Processable Electronics, Imperial College London, South Kensington, London SW7 2AZ, U.K.
⁴ Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.
⁵ School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, U.K.

PMID: 34365787
DOI: 10.1021/acsami.1c09750

Abstract

Copper(I) thiocyanate (CuSCN) is a stable, low-cost, solution-processable p-type inorganic semiconductor used in numerous optoelectronic applications. Here, for the first time, we employ the time-of-flight (ToF) technique to measure the out-of-plane hole mobility of CuSCN films, enabled by the deposition of 4 μm-thick films using aerosol-assisted chemical vapor deposition (AACVD). A hole mobility of ∼10^-3 cm²/V s was measured with a weak electric field dependence of 0.005 cm/V^1/2. Additionally, by measuring several 1.5 μm CuSCN films, we show that the mobility is independent of thickness. To further validate the suitability of our AACVD-prepared 1.5 μm-thick CuSCN film in device applications, we demonstrate its incorporation as a hole transport layer (HTL) in methylammonium lead iodide (MAPbI₃) perovskite solar cells (PSCs). Our AACVD films result in devices with measured power conversion efficiencies of 10.4%, which compares favorably with devices prepared using spin-coated CuSCN HTLs (12.6%), despite the AACVD HTLs being an order of magnitude thicker than their spin-coated analogues. Improved reproducibility and decreased hysteresis were observed, owing to a combination of excellent film quality, high charge-carrier mobility, and favorable interface energetics. In addition to providing a fundamental insight into charge-carrier mobility in CuSCN, our work highlights the AACVD methodology as a scalable, versatile tool suitable for film deposition for use in optoelectronic devices.

Keywords: copper(I) thiocyanate; hole transport material; out-of-plane hole mobility; perovskite solar cells; time-of-flight technique.