Low-Temperature Fabrication and Performance of Polycrystalline CuI Films as Transparent p-Type Semiconductors

Transparent p-type polycrystalline CuI films with high hole mobility are produced by solid iodination of Cu3N precursor layers and subsequent heat treatment at 120 degrees C. The hole mobility reached 20 cm(2) V-1 s(-1) in the CuI films fabricated on both glass and polyethylene terephthalate substrates. Furthermore, transparent p-n diodes with sufficiently high rectification ratio (6 x 10(6)) and ideality factor (1.6) are successfully fabricated by employing a heterojunction of p-type CuI and n-type amorphous In-Ga-Zn-O (a-IGZO) layers. The CuI/a-IGZO heterojunction exhibits the photovoltaic effect, with a short-circuit current of 0.33 mu A and an open-circuit voltage of 10 mV under UV illumination at a wavelength of 365 nm and intensity of 1.9 mW cm(-2). The photoresponse at zero bias is sufficiently quick, and thus, the photovoltaic properties of the CuI/a-IGZO diodes rendere them potential candidates for visible-light-blind and self-powered UV photodetectors. These findings suggest that CuI is an excellent transparent p-type semiconductor that can be fabricated at low temperature.