Enhanced saturable absorption induced by Pauli blocking and radiation-induced trapping with negative photoresponse in Cr2O3/MoS2/PEDOT:PSS

Abstract

We have successfully shown a method to considerably modify the nonlinear saturable absorption characteristics of nanocomposite films (NCFs) composed of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT:PSS), molybdenum disulfide (MoS2), and chromium (III) oxide (Cr2O3). Furthermore, a transition from negative to positive photoresponse was observed under UV illumination by adjusting the concentration of Cr2O3. Various concentrations of Cr2O3 were incorporated into the NCF to produce films using a simple drop-casting method on a glass substrate. Optical properties, specifically the refractive index (n) and extinction coefficient (k), of the resulting NCFs were assessed using the Kramers–Kronig equations. Nonlinear studies revealed the changes in the optical nonlinearity of pure PEDOT:PSS upon combination with MoS2 and Cr2O3. In particular, the occurrence of Pauli blocking was observed in Cr2O3/MoS2/PEDOT:PSS NCFs, leading to improved saturable absorption within the NCF structure. Additionally, a negative photoresponse to UV light exposure was observed, which is attributed to the trapping and confinement of charges generated by the radiation. These results highlight the negative photoresponse and notable saturable absorption qualities, suggesting intriguing directions for additional research into the photoresponse and nonlinear optical features of NCFs.