Out-of-plane photoconductive and bulk photovoltaic effects in two-dimensional a-In2Se3/Ta2NiS5 ferroelectric heterojunctions

Two-dimensional a-In2Se3 exhibits simultaneous intercorrelated in-plane and out-of-plane polarization, making it a highly promising material for use in memories, synapses, sensors, detectors, and optoelectronic devices. With its narrow bandgap, a-In2Se3 is particularly attractive for applications in photodetection. However, relatively little research has been conducted on the out-of-plane photoconductive and bulk photovoltaic effects in a-In2Se3. This limits the potential of a-In2Se3 in the device innovation and performance modification. Herein, we have developed an a-In2Se3-based heterojunction with a transparent electrode of two-dimensional Ta2NiS5. The out-of-plane electric field can effectively separate the photo-generated electron-hole pairs in the heterojunction, resulting in an out-of-plane responsivity (R), external quantum efficiency (EQE), and specific detectivity (D*) of 0.78 mA/W, 10-3 % and 1.14 x 10(8) Jones, respectively. The out-of-plane bulk photovoltaic effect has been demonstrated by changes in the short circuit current (SCC) and open circuit voltage (Voc) with different optical power intensity and temperature, which indicates that a-In2Se3-based heterojunctions has application potential in mid-far infrared light detection based on its out-of-plane photoconductive and bulk photovoltaic effects. Although the out-of-plane photoconductive and bulk photovoltaic effects are relatively lower than that of traditional materials, the findings pave the way for a better understanding of the out-of-plane characteristics of two-dimensional a-In2Se3 and related heterojunctions. Furthermore, the results highlight the application potential of a-In2Se3 in low-power device innovation and performance modification.