Photoluminescence Quenching and Photoconductivity in Devices Using 3,6-Diaryl-<i>N</i>-hexylcarbazole

Photocarrier generation mechanisms in 3,6-diaryl-<i>N</i>-hexylcarbazole (aryl = <i>p</i>-cyanophenyl and <i>p</i>-acetophenyl) were studied in single-layer, bilayer, and blend film devices in sandwich geometry between indium–tin oxide (ITO) and Al electrodes. Bilayer and blend film devices were made with <i>N</i>,<i>N</i>′-diphenyl-<i>N</i>,<i>N</i>′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD). Photoluminescence (PL) was strongly quenched by electric field. The photocurrent versus electric field plots and photoresponse action spectra were used to identify the source of photocarrier generation (interface versus bulk) in the three devices. In blend devices, the photocurrent density is directly proportional to PL quenching efficiency, indicating efficient carrier generation and collection in these devices. PL quenching and photocurrent results were fitted to theoretical equations to obtain material parameters such as exciton binding energy, exciton dissociation rate at zero field, PL quenching efficiency at zero field, and carrier mobility-lifetime product. The device properties of the two carbazole derivatives are suitable for visible-blind UV photodetectors

Superconducting Cavity-Based Sensing of Band Gaps in 2D Materials

The superconducting coplanar waveguide (SCPW) cavity plays an essential role in various areas like superconducting qubits, parametric amplifiers, radiation detectors, and studying magnon-photon and photon-phonon coupling. Despite its wide-ranging applications, the use of SCPW cavities to study various van der Waals 2D materials has been relatively unexplored. The resonant modes of the SCPW cavity exquisitely sense the dielectric environment. In this work, we measure the charge compressibility of bilayer graphene coupled to a half-wavelength SCPW cavity. Our approach provides a means to detect subtle changes in the capacitance of the bilayer graphene heterostructure, which depends on the compressibility of bilayer graphene, manifesting as shifts in the resonant frequency of the cavity. This method holds promise for exploring a wide class of van der Waals 2D materials, including transition metal dichalcogenides (TMDs) and their moiré, where DC transport measurement is challenging