Room temperature fabricated flexible NiO/IGZO pn diode under mechanical strain

•p-Type semiconducting NiO is deposited by room temperature sputtering.•NiO and IGZO are used to fabricate pn diodes on free-standing plastic substrate.•Tensile and compressive strain induced by bending is applied to the flexible diodes.•Application under strain is demonstrated by the rectification of a 50 Hz AC signal.

Flexible electronic devices fabricated on plastic substrates require semiconductors, which can be deposited at low temperatures. While Indium–Gallium–Zinc-Oxide (IGZO) is a promising n-type oxide semiconductor, a p-type oxide semiconductor with similar performance is currently not available. Here, the room temperature deposition of nickel oxide (NiO) acting as a p-type oxide semiconductor on a flexible plastic foil is described. NiO exhibits a carrier density of +1.6 × 1017 cm−3 and a Hall mobility of 0.45 cm2/Vs. p-type NiO is combined with n-type IGZO to fabricate flexible pn diodes on a free-standing polyimide substrate. The diodes show an ideality factor of ≈3.2 and an on–off current-ratio of ≈104. The NiO/IGZO diodes stay fully operational when exposed to tensile or compressive mechanical strain of 0.25%, induced by bending to a radius of 10 mm. In addition, a 50 Hz AC signal was rectified using a flexible diode while flat and bent.