Transparent semiconductor oxides with two-dimensional (2D) heterostructures have been extensively
studied as new materials for thin-film transistors and photosensors due to their remarkable photovoltaic
characteristics, making them useful for newly developed optoelectronics. Here we demonstrate the fabrication
and characterization of an ITO/n-IGZO/p-GeSe transparent selective wavelength photodetector.
The wavelength-dependent photovoltaic behavior of the n-IGZO/p-GeSe heterostructure under
UV-Visible laser light shifts the I–V curves down with positive Voc and negative Isc values of about 0.12 V
and −49 nA and 0.09 V and −17 nA, respectively. Interestingly, when an NIR laser irradiated the device, the
I–V curves shifted up with negative Voc and positive Isc values of about −0.11 V and 45 nA, respectively.
This behavior is attributed to the free carrier concentration induced by photogenerated carriers across the
device at different points that varied with the wavelength-dependent photon absorption. Consequently,
the direction of the electric field polarity across the junction can be flipped. This study demonstrates a
zero-bias near-infrared (NIR) photodetector with a high photoresponsivity of 538.9 mA W−1, a fast rise
time of 25.2 ms, and a decay time of 25.08 ms. Furthermore, we observed a detectivity (D) of 8.4 × 109
Jones, a normalized photocurrent to dark current ratio (NPDR) of 2.8 × 1010 W−1, and a noise equivalent
power (NEP) of 2.2 × 10−14 W Hz−1/2. Our strategy opens alternative possibilities for scalable, low-cost,
multifunctional transparent near-infrared photosensors with selective wavelength photodetection.