Zero Bias Operation: Photodetection Behaviors Obtained by Emerging Materials and Device Structures

Quantum Graphene Asymmetric Devices for Harvesting Electromagnetic Energy

We present here the fabrication at the wafer level and the electrical performance of two types of graphene diodes: ballistic trapezoidal-shaped graphene diodes and lateral tunneling graphene diodes. In the case of the ballistic trapezoidal-shaped graphene diode, we observe a large DC current of 200 µA at a DC bias voltage of ±2 V and a large voltage responsivity of 2000 v/w, while in the case of the lateral tunneling graphene diodes, we obtain a DC current of 1.5 mA at a DC bias voltage of ±2 V, with a voltage responsivity of 3000 v/w. An extended analysis of the defects produced during the fabrication process and their influences on the graphene diode performance is also presented.

Imitating Synapse Behavior: Exploiting Off-Current in TPBi-Doped Small Molecule Phototransistors for Broadband Wavelength Recognition

Phototransistors have gained significant attention in diverse applications such as photodetectors, image sensors, and neuromorphic devices due to their ability to control electrical characteristics through photoresponse. The choice of photoactive materials in phototransistor research significantly impacts its development. In this study, we propose a novel device that emulates artificial synaptic behavior by leveraging the off-current of a phototransistor. We utilize a p-type organic semiconductor, dinaphtho[2,3-b:2',3'- f]thieno[3,2-b]thiophene (DNTT), as the channel material and dope it with the organic semiconductor 2,2',2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) on the DNTT transistor. Under light illumination, the general DNTT transistor shows no change in off-current, except at 400 nm wavelength, whereas the TPBi-doped DNTT phototransistor exhibits increased off-current across all wavelength bands. Notably, DNTT phototransistors demonstrate broad photoresponse characteristics in the wavelength range of 400-1000 nm. We successfully simulate artificial synaptic behavior by differentiating the level of off-current and achieving a recognition rate of over 70% across all wavelength bands.