A high-performance broadband organic flexible photodetector from a narrow-bandgap thiazolo[5,4-d]thiazole containing conjugated polymer

Abstract

Our present study developed high-performance organic photodetectors (OPDs) with broad-spectrum capabilities utilizing a thiazolo[5,4-d]thiazole containing a high-mobility conjugated polymer P-TZTZ. The low bandgap polymer with 2D nanosheet morphology is synthesized by an easy condensation reaction between dithiooxamide and terephthalaldehyde. Based on the used substrate (Si-wafer and PET substrate), two variants of the proposed photodetectors were fabricated. Both variants of the fabricated photodetectors (PDs) demonstrated comparable photodetection capabilities in a broad region from 400 to 1000 nm. Under the presence of a broadband white light source, the peak photo-to-dark current ratio (PDCR) values for the PD fabricated on Si-substrate (PD1) are calculated to be 42.58 and 5.68 at the bias voltage (V_B) of −0.1 and +1.0 V, respectively. Similarly, the PD fabricated on ITO-coated PET substrate (PD2) under the influence of a broadband white light source offered PDCR values of 8.65 and 7.25 at a V_B of −4 V and +4 V, respectively. Experimental findings indicate that the fabricated PD1 achieves a peak responsivity of 2.12 A W⁻¹ at 410 nm with peak external quantum efficiency (EQE) values of 6.41% and 4.32% at 410 and 530 nm, respectively. The specific detectivity (D) values are estimated to be 4.42 × 10¹³ Jones at 410 nm and 3.71 × 10¹³ Jones at 530 nm. Similarly, the fabricated PD2 achieves the peak responsivity, external quantum efficiency, and specific detectivity values of 1.98 A W⁻¹, 5.9% and 1.71 × 10¹³ Jones at 410 nm, respectively. Transient performance analysis revealed that the P-TZTZ-based flexible PD exhibited rise and fall times of 180 ms and 100 ms, respectively. The high responsivity, detectivity, and millisecond-order switching time in rigid and flexible P-TZTZ-based PDs demonstrate the versatility and potential for diverse applications covering from rigid to flexible electronics.