Zinc phosphide

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| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 470636688
| Name = Zinc phosphide
| Reference =
| ImageFile = Zn3P2structure. jpg
| ImageSize =
| ImageName = Zinc phosphide
| OtherNames = trizinc diphosphide
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|Section7=Chembox Hazards
| ExternalSDS = ThermoFisher Scientific, revised 02/2020
| GHSSignalWord = Danger
| IngestionHazard = Fatal, acutely toxic
| InhalationHazard = High
| HPhrases =
| PPhrases =
| NFPA H = 4
| NFPA R = 2
| NFPA F = 3
| NFPA S = W
| NFPA ref = Zn3P2 is a II V semiconductor with a direct band gap of 1.5 eV and may have applications in photovoltaic cells. A second compound exists in the zinc phosphorus system, zinc diphosphide (ZnP2).

Zn3P2 has a room temperature tetragonal form that converts to a cubic form at around 845 °C. In the room temperature form there are discrete P atoms, zinc atoms are tetrahedrally coordinated and phosphorus six coordinate, with zinc atoms at 6 of the vertices of a distorted cube. The crystalline structure of zinc phosphide is very similar to that of cadmium arsenide (Cd3As2), zinc arsenide (Zn3As2) and cadmium phosphide (Cd3P2). These compounds of the Zn Cd P As quaternary system exhibit full continuous solid solution.

Zinc phosphide is an ideal candidate for thin film photovoltaic applications, for it has strong optical absorption and an almost ideal band gap (1.5eV). In addition to this, both zinc and phosphorus are found abundantly in the Earth's crust, meaning that material extraction cost is low compared with that of other thin film photovoltaics. Both zinc and phosphorus are also nontoxic, which is not the case for other common commercial thin film photovoltaics, like cadmium telluride. Researchers at the University of Alberta were the first to successfully synthesize colloidal zinc phosphide. Before this, researchers were able to create efficient solar cells from bulk zinc phosphide, but their fabrication required temperatures greater than 850 °C or complicated vacuum deposition methods. By contrast, colloidal zinc phosphide nanoparticles, contained in a zinc phosphide “ink”, allows for inexpensive, easy large scale production, by means of slot die coating or spray coating. The testing and development of these zinc phosphide thin films is still in its early stages, but early results have been positive. Prototype heterojunction devices fabricated from zinc phosphide nanoparticle ink exhibited a rectification ratio of 600 and photosensitivity with an on/off ratio near 100. These are both acceptable suitability benchmarks for solar cells. Development still needs to be made on optimizing the nanoparticle ink formation and device architecture before commercialization is possible, but commercial spray on zinc phosphide solar cells may be possible within ten years.

The New Zealand Environmental Protection Authority has approved the import and manufacture of Microencapsulated Zinc Phosphide (MZP Paste) for the ground control of possums. The application was made by Pest Tech Limited, with support from Connovation Ltd, Lincoln University and the Animal Health Board. It will be used as an additional vertebrate poison in certain situations. Unlike 1080 poison, it cannot be used for aerial application.

Zinc phosphide is highly toxic, especially when ingested or inhaled. The reason for its toxicity is the release of phosphorus compounds, usually phosphine, when it reacts with water and acids. Phosphine is very toxic and, with trace amounts of P2H4, pyrophoric. Phosphine is also denser than air and may remain close to the ground without sufficient ventilation.