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In this work, we report a simple method for solution-processed organic light emitting devices (OLEDs), where single-layer graphene acts as the anode and the hexa-peri-hexabenzocoronene exfoliating agent (HBC-6ImBr) provides surface modification. In SEM images, the PEDOT:PSS solution fully covered the graphene electrode after coating with HBC-6ImBr. The fabricated solution-processed OLEDs with a single-layer graphene anode showed outstanding brightness at 3182 cd/m² and current efficiency up to 6 cd/A which is comparable to that of indium tin oxide films, and the OLED device brightness performance increases six times compared to tri-layer graphene treated with UV-Ozone at the same driving voltage. This method can be used in a wide variety of solution-processed organic optoelectronics on surface-modified graphene anodes. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, bismuth iodide (BiI3), a layered metal halide semiconducting light absorber with a wide bandgap of ≈1.8 eV and strong optical absorption in the visible region, has received greater attention for photovoltaic applications. In this study, ultrasensitive visible‐light photodetectors with graphene/BiI3 vertical heterostructures are achieved by van der Waals epitaxies. The BiI3 films deposited on graphene show flatter morphologies and significantly better crystallinities than that of BiI3 films on SiO2 substrates, mainly due to weak van der Waals interactions at the graphene/BiI3 interface. Hybrid photodetectors with highly crystalline graphene/BiI3 heterostructures demonstrate an ultrahigh responsivity of 6 × 106 A W−1, shot‐noise‐limited detectivity of 7 × 1014 Jones, and a relatively short response time of ≈8 ms. Compared to most previously reported graphene‐based hybrid photodetectors, these devices have comparable photosensitivities but a faster response speed and lower operation voltage, which is quite promising for ultralow intensity visible‐light sensors. Moreover, the electronic structure and interfacial chemistry at the graphene/BiI3 heterojunctions are investigated using photoemission spectroscopy. The results give clear evidence that no chemical interactions occur between graphene and BiI3, resulting in the van der Waals epitaxial growth, and the measured band bending consistently illustrates that a photoinduced charge transfer occurs at the graphene/BiI3 interface. [ABSTRACT FROM AUTHOR]

In this work, graphene-methylammonium lead iodide (MAPbI3) perovskite hybrid phototransistors fabricated by sequential vapor deposition are demonstrated. Ultrahigh responsivity of 1.73 × 107 A W−1 and detectivity of 2 × 1015 Jones are achieved, with extremely high effective quantum efficiencies of about 108% in the visible range (450-700 nm). This excellent performance is attributed to the ultra-flat perovskite films grown by vapor deposition on the graphene sheets. The hybrid structure of graphene covered with uniform perovskite has high exciton separation ability under light exposure, and thus efficiently generates photocurrents. This paper presents photoluminescence (PL) images along with statistical analysis used to study the photo-induced exciton behavior. Both uniform and dramatic PL intensity quenching has been observed over entire measured regions, consistently demonstrating excellent exciton separation in the devices. [ABSTRACT FROM AUTHOR]