Abstract
Phosphides are interesting candidates for hole transport materials and p-type transparent conducting applications, capable of achieving greater valence band dispersion than their oxide counterparts due to the higher lying energy and increased size of the P 3p orbital. After computational identification of the indirect-gap semiconductor CaCuP as a promising candidate, we now report reactive sputter deposition of phase-pure p-type CaCuP thin films. Their intrinsic hole concentration and hole mobility exceed 1 × 1020 cm−3 and 35 cm2 V−1 s−1 at room temperature, respectively. Transport calculations indicate potential for even higher mobilities. Copper vacancies are identified as the main source of conductivity, displaying markedly different behaviour compared to typical p-type transparent conductors, leading to improved electronic properties. The optical transparency of CaCuP films is lower than expected from first principles calculations of phonon-mediated indirect transitions. This discrepancy could be partly attributed to crystalline imperfections within the films, increasing the strength of indirect transitions. We determine the transparent conductor figure of merit of CaCuP films as a function of composition, revealing links between stoichiometry, crystalline quality, and opto-electronic properties. These findings provide a promising initial assessment of the viability of CaCuP as a p-type transparent contact.
| Original language | English |
|---|---|
| Pages (from-to) | 5872-5883 |
| Number of pages | 12 |
| Journal | Chemical Science |
| Volume | 13 |
| Issue number | 20 |
| Early online date | 26 Apr 2022 |
| DOIs | |
| Publication status | Published - 28 May 2022 |
Bibliographical note
Funding Information:This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 840751 (synthesis, characterization, and experimental data analysis work). This work was authored in part at the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under contract no. DE-AC36-08GO28308. The views expressed in this article do not necessarily represent the views of the DOE or the US government. Funding supporting development and operation of synthesis and characterization equipment (RRS, KNH, AZ) was provided by the Office of Science, Office of Basic Energy Sciences. JW and DOS acknowledge Diamond Light Source Ltd for co-sponsorship of an EngD studentship on the EPSRC Centre for Doctoral Training in Molecular Modelling and Materials Science (EP/L015862/1). This work used the ARCHER and ARCHER2 UK National Supercomputing Service ( https://www.archer2.ac.uk ), via our membership of the UK's HEC Materials Chemistry Consortium, which is funded by the EPSRC (EP/L000202, EP/R029431 and EP/T022213), and the UK Materials and Molecular Modelling (MMM) Hub (Thomas EP/P020194 and Young EP/T022213). The UCL Grace, Kathleen and Thomas HPC Facilities (Grace@UCL, Kathleen@UCL, Thomas@UCL) were also used in the completion of this work. JW thanks Dr Anna Regoutz and Dr Benjamin A. D. Williamson for insightful discussions about this project. AC thanks Dr Sage Bauers for assistance with electrical measurements. IB and BM acknowledge support from the Winton Programme for Physics of Sustainability. BM also acknowledges support from a UKRI Future Leaders Fellowship (grant no. MR/V023926/1) and from the Gianna Angelopoulos Programme for Science, Technology and Innovation. This work made use of resources provided by the Cambridge Tier-2 system, operated by the University of Cambridge Research Computing Service ( https://www.hpc.cam.ac.uk ) and funded by Tier-2 capital grant EP/P020258/1.
Publisher Copyright:
© 2022 The Royal Society of Chemistry
ASJC Scopus subject areas
- General Chemistry