High-Performance Self-Powered Transparent Metal–Semiconductor-Metal Ultraviolet Photodetector Based on Sub-10 nm Thick Dual-Asymmetric Interdigitated Electrodes

Transparent self-powered ultraviolet (UV) photodetectors (PDs) are demonstrated experimentally with dual-asymmetric interdigitated electrodes composed of Au and Ag with different sizes on top of a ZnO active layer. The electrodes are sub-10 nm thick and highly transparent in both UV and visible regimes, making the whole device look transparent and output light current over 1/3 higher than that of the counterpart with thick opaque electrodes at 0 V. The PD with only electrode material asymmetry can work at 0 V because of the Schottky junction formed at the Au/ZnO interface and the Ohmic contact at the Ag/ZnO interface. The junction asymmetry can be further enhanced by the electrode size difference. The PD with a Au and Ag finger width ratio of 1:4 achieves a photocurrent over 11 times that of the device with identical Au and Ag sizes. A high responsivity of 56.3 μA/W and a high detectivity of 1.54 × 108 Jones are achieved. The rise and fall times are as low as 3.1 and 2.8 ms, respectively. By patterning the pads, our PD becomes more uniform and transparent with an average visible transmissivity improved to 77.6% (the highest among the UV PD chips reported), while the optoelectronic conversion performance remains unchanged. The overall properties are comparable and even superior to those of the previously reported counterparts. This work provides insights into the design and mechanism of transparent self-powered UV PDs, facilitating advancements in this field.