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 the hybrid DPPTT coated MoS₂ phototransistor is higher, R = 398 A/W compared to its pristine MoS₂, R = 155 A/W at V_g = 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 hybrid heterostructure with IR absorbing polymer may pave the way to design the high sensitivity IR photodetector for promising optoelectronic applications.