Cu2P3I2 wires were synthesized and converted to Ag2P3I2 via post-synthetic modification. Single-wire and thin film devices were constructed from each material and evaluated as rapidly reversible humidity sensing semiconductors. All devices exhibited a dramatic increase in current when exposed to a ~30.85% RH (~9745.3 ppm by moisture volume) atmosphere compared to that of dry N2. Cu2P3I2 devices exhibited greater sensitivity compared to their respective Ag2P3I2 analogs with the highest being the thin film at 2.43 × 10−8 A% RH. While all devices exhibited rapid (<5 s) reversibility, the thin film devices exhibited greater sensitivity compared to their single-wire forms.

In an attempt to widen the family of Phosphorus Metal Halides (MxPyXz) and enable new applications, post-synthetic modifications to the MxPyXz, Cu2P3I2 have been reported. While such a technique suggests access to an entirely new family of MxPyXz-based materials, we report, in this work, that the ion-exchange process seemingly influences important properties such as the crystallographic pattern and vibrational modes.