Enhanced Infrared Photosensitivity in DPP based Polymer Sensitized MoS₂ Phototransistor

Two-dimensional semiconductors particularly Transition Metal Dichalcogenides (TMDCs) hold promising potential in future optoelectronic applications due to their high photoresponsivity and tunable band structure for broadband photodetection. Infrared (IR) photodetectors play a key role in various applications, including image sensing, communications, environmental monitoring, remote control, day and night-time surveillance, and chemical/biological sensing. Photo response of 2D TMDCs materials in the IR spectral region is one of the challenging tasks due to their band edge absorption. Here, we report the high photo-response behavior of a few-layered MoS₂ Field-effect Transistor (FET), sensitizing the surface of MoS₂ with IR absorbing DPPTT polymer. The proposed photodetector sensitized with DPPTT polymer shows an enhanced photocurrent response under the IR spectral range from 800 nm – 1050 nm with a high photocurrent responsivity of R = 10³ A/W where the pristine MoS₂ phototransistor fails to produce any responsivity. The photocurrent of the pristine MoS₂ phototransistor and the DPPTT polymer sensitized MoS₂ phototransistors are measured under white light illumination using a halogen lamp source. Under the white light, the R value of hybrid DPPTT coated MoS₂ phototransistor is higher, R = 398 A/W compared to its pristine MoS₂, R = 155 A/W at V_bg = 20V. The large photo response in the hybrid phototransistor device is due to the increase of IR absorption on DPPTT polymer and subsequent charge transfer to the MoS₂ layers. Photo-to-Dark Current Ratio (PDCR) in our hybrid MoS₂/Polymer Phototransistor is 70 at 800 nm and decreased to 10 at 1050 nm and Detectivity (D) in the range of 10¹¹ to 10⁹. Our study revealed that 2D semiconductor with IR absorbing polymer may pave the way to design the high sensitivity IR photodetector for promising optoelectronic applications.