Towards defect-free thin films of the earth-abundant absorber zinc phosphide by nanopatterning

Large-scale deployment of thin-film photovoltaics will be facilitatedthrough earth-abundant components. Herein, selective area epitaxyand lateral overgrowth epitaxy are explored for the growth of zincphosphide (Zn3P2), a promising earth-abundant absorber. The idealgrowth conditions are elucidated, and the nucleation of single-crystalnanopyramids that subsequently evolve towards coalesced thin-filmsis demonstrated. The zinc phosphide pyramids exhibit room temper-ature bandgap luminescence at 1.53 eV, indicating a high-qualitymaterial. The electrical properties of zinc phosphide and the junc-tion with the substrate are assessed by conductive atomic forcemicroscopy on n-type, p-type and intrinsic substrates. The measure-ments are consistent with the p-type characteristic of zinc phosphide.Overall, this constitutes a new, and transferrable, approach for thecontrolled and tunable growth of high-quality zinc phosphide, a stepforward in the quest for earth-abundant photovoltaics.