Photo-controlled programmable logic gate via self-powered Cu2O/BiFeO3/TiO2 ferroelectric heterojunction photodetectors

The increased demands for high integration, fast computation, and a wide range of data processing in digital logic circuits have triggered an interest in programmable logic gates that can run different logic operations. Photodetectors (PDs) based on ferroelectric materials can obtain different ferroelectric polarization states utilizing pre-biased voltage regulation to achieve programmable logic functions, but low photoelectric conversion efficiency and slow photoresponse speed are still key problems to be addressed for programmable logic gate devices. Herein, the Cu2O/BiFeO3(BFO)/TiO2 ferroelectric heterojunction PDs were constructed by introducing a p-type hole transport layer Cu2O on the BFO/TiO2 ferroelectric heterojunction films, which not only broadens the photoresponse spectra range to the red light, but also forms a stepped energy band structure at the heterojunction interface, and the interfacial electric field promotes the separation and transport of photogenerated carriers, improving the self-powered photodetection performance of the devices. The Cu2O/BFO/TiO2 PDs demonstrate a responsivity of 3.0mA/W and a photoresponse rise time/decay time of 2.3/23.9 ms at 420nm light illumination. The Cu2O/BFO/TiO2 PD can be polarized in different states by pre-biased voltage and outputs different electrical signal values under the ultraviolet (365nm) and visible (420nm) monochromatic light or the mixed light irradiation, thus the device can realize the "AND" gate output in the positive bias polarization state and the "OR" gate output in the negative bias polarization state, which shows that the ferroelectric heterojunction PDs has a great potential application in the field of photo-controlled programmable logic gate circuits.