Heterostructures with built‐in electric fields are crucial for charge separation and lateral photovoltaic effect in current position‐sensitive detectors (PSDs), which have to be produced by combining semiconductors with metal or other semiconductors to form various vertical junctions (e.g. Schottky junctions) via complicated and high‐cost manufacture processes. In the present work, it was found that vertical junctions can be directly written and patterned inside graphene oxide (GO) films with gradient C/O ratios by laser scribing due to the optical filter effect of the films and the formation of reduced GO (rGO) layers. Such junctions were verified to show the capability for high‐precision position sensing on the micrometer scale, owing to the lateral photovoltaic effect. These self‐powered laser‐scribed PSDs can exhibit a small nonlinearity of <5.4%, which is far less than the acceptable level of 15%. A fast response time of about 1 ms can be obtained under a zero bias voltage, which is the fastest speed among the photodetectors based on pure rGO. Electron lateral diffusion in the upper layers of the laser‐scribed devices was found to play a main role. These suggest that laser‐scribed vertical junctions inside rGO are promising for high‐precision displacement sensing, with the capability of low cost, flexibility, and passive operation mode.

Numerous molecular ferroelectrics having excellent properties even comparable to inorganic ones, which usually contain heavy or toxic metals, have been developed recently. Hopefully, they can be used as substitutes for the well-known organic ferroelectric polymers (P(VDF-TrFE)) with huge coercive fields and poor spontaneous polarization for various applications. However, the bottleneck for practical applications, i.e., the preparation of high-quality thin films and high resolution device arrays with a desired crystallographic orientation for memory switching, still remains. In this study, large-area micro device arrays of molecular ferroelectrics with highly-crystalline or even single-crystalline films are intentionally self-assembled on electrodes or within electrode gaps using a solution processing technique, including the molecular ferroelectrics for which it is usually difficult to make thin films. The as-grown air-stable memory micro arrays with an optimum crystallographic orientation can exhibit excellent non-volatile memory performance with a smaller operation voltage of <5 V. These attributes can pave the way for molecular ferroelectrics to become a promising candidate for applications including flexible memories and circuits.

Photoinduced space-charges in organic optoelectronic devices, which are usually caused by poor mobility and charge injection imbalance, always limit the device performance. Here we demonstrate that photoinduced space-charge layers, accumulated at organic semiconductor-insulator interfaces, can also play a role for photocurrent generation. Photocurrent transients from organic devices, with insulator-semiconductor interfaces, were systematically studied by using the double-layer model with an equivalent circuit. Results indicated that the electric fields in photoinduced space-charge layers can be utilized for charge generation and can even induce a photovoltage reversal. Such an operational process of light harvesting would be promising for photoelectric conversion in organic devices.

Graphene-based optoelectronic devices, including reduced graphene oxide (RGO) devices, commonly exhibit a large dark current and low on/off ratio with high dark-power consumption and a small responsivity. In this study, semi-RGO-based infrared photodetectors were directly "written" by using lasers, which can exhibit a small dark current of approximately 12 µA/cm² with a high responsivity of approximately 0.18 A/W at 1,550 nm. Both the dark current and response speed can be tuned with GO as the gate dielectric in a field-effect transistor structure. These findings suggest the possibility of the three-dimensional "writing" of a micro-optoelectronic device or system with a low cost and high performance.