Nevertheless, band alignment calculations show that the ionisation potential of CaCuP matches the valence band position of various semiconductors of technological interest. Thus, it may be possible to integrate CaCuP as a contact layer into device structures where full transparency is not required. We call on the community for further experimental investigation of CaCuP with focus on its optical properties. Growth of high-quality single crystals would be particularly useful to investigate if the high absorption coefficient of the present CaCuP samples is an intrinsic feature of the material or the consequence of a less-than-ideal growth process. Beyond-DFT calculations that provide an improved description of the band gap (GW theory) and excited states (Bethe-Salpeter formalism) would also provide a clearer picture of the optical properties of CaCuP. Finally, exploration of other thin-film synthesis routes, epitaxial growth, and extrinsic doping would help to build a more robust assessment of CaCuP as a transparent conductor and opto-electronic material in general.