All-inorganic lead halide perovskite quantum dots (IHP QDs) have great potentials in photodetectors. However, the photoresponsivity is limited by the low charge transport efficiency of the IHP QD layers. High-performance phototransistors based on IHP QDs hybridized with organic semiconductors (OSCs) are developed. The smooth surface of IHP QD layers ensures ordered packing of the OSC molecules above them. The OSCs significantly improve the transportation of the photoexcited charges, and the gate effect of the transistor structure significantly enhances the photoresponsivity while simultaneously maintaining high I /I ratio. The devices exhibit outstanding optoelectronic properties in terms of photoresponsivity (1.7 × 10 A W ), detectivity (2.0 × 10 Jones), external quantum efficiency (67000%), I /I ratio (8.1 × 10 ), and stability (100 d in air). The overall performances of our devices are superior to state-of-the-art IHP photodetectors. The strategy utilized here is general and can be easily applied to many other perovskite photodetectors.

A high-quality perovskite film with interconnected perovskite grains was obtained by incorporating terephthalic acid (TPA) additive into the perovskite precursor solution. The presence of TPA changed the crystallization kinetics of the perovskite film and promoted lateral growth of grains in the vicinity of crystal boundaries. As a result, sheet-shaped perovskite was formed and covered onto the bottom grains, which made some adjacent grains partly merge together to form grains-interconnected perovskite film. Perovskite solar cells (PSCs) with TPA additive exhibited a power conversion efficiency (PCE) of 18.51% with less hysteresis, which is obviously higher than that of pristine cells (15.53%). PSCs without and with TPA additive retain 18 and 51% of the initial PCE value, respectively, aging for 35 days exposed to relative humidity 30% in air without encapsulation. Furthermore, MAPbI film with TPA additive shows superior thermal stability to the pristine one under 100 °C baking. The results indicate that the presence of TPA in perovskite film can greatly improve the performance of PSCs as well as their moisture resistance and thermal stability.

Hole transport layer NiOx-based inverted perovskite solar cells (PSCs) have advantages of simple fabrication, low temperature, and low cost. Furthermore, the p-type NiOx material compared to that of typical n-type SnOx for PSCs has better photostability potential due to its lower photocatalytic ability. However, the NiOx layer modified by some typical materials show relatively simple functions, which limit the synthesized performance of NiOx-based inverted PSCs. Phenethyl ammonium iodide (PEAI) was introduced to modify the NiOx/perovskite interface, which can synchronously contribute to better crystallinity and stability of the perovskite layer, passivating interface defects, formed quasi-two-dimensional PEA2PbI4 perovskite layers, and superior interface contact properties. The PCEs of PSCs with the PEAI-modified NiOx/perovskite interface was obviously increased from 20.31 from 16.54% compared to that of the reference PSCs. The PSCs with PEAI modification remained 75 and 72% of the original PCE values aging for 10 h at 85 °C and 65 days in a relative humidity of 15%, which are superior to the original PCE values (47 and 51%, respectively) for the reference PSCs. Therefore, PSCs with the PEAI-modified NiOx/perovskite interface show higher PCEs and better thermal stability and moisture resistance.

Planar perovskite solar cells (PSCs) that use nickel oxide (NiO) as a hole transport layer have recently attracted tremendous attention because of their excellent photovoltaic efficiencies and simple fabrication. However, the electrical conductivity of NiO and the interface contact properties of the NiO/perovskite layer are always limited for the NiO layer fabricated at a relatively low annealing temperature. Ferrocenedicarboxylic acid (FDA) was firstly introduced to modify a p-type NiO hole transport layer in PSCs, which obviously improves the crystallization of the perovskite layer and hole transport and collection abilities and reduces carrier recombination. PSCs with a FDA modified NiO layer reached a PCE of 18.20%, which is much higher than the PCE (15.13%) of reference PSCs. Furthermore, PSCs with a FDA interfacial modification layer show better UV durability and a hysteresis-free effect and still maintain the original PCE value of 49.8%after being exposed to UV for 24 h. The enhanced performance of the PSCs is attributed to better crystallization of the perovskite layer, the passivation effect of FDA, superior interface contact at the NiO/perovskite layers and enhancement of the electrical conductivity of the FDA modified NiO layer. In addition, PSCs with FDA inserted at the interface of the perovskite/PCBM layers can also improve the PCE to 16.62%, indicating that FDA have dual functions to modify p-type and n-type carrier transporting layers.

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A two-step polarization reversal process was identified in the pentacene/poly(vinylidene fluoride-trifluoroethylene) double-layer device. Displacement current measurement showed that three peaks generated non-symmetrically in the current-voltage characteristics. Accordingly, optical electric-field induced second-harmonic generation measurement displayed two hysteresis loops. A proposed model based on a two-step polarization reversal mechanism accounted for these results, and suggested that interaction of interfacial charge and ferroelectric polarization governed the mechanism. The proposed model is useful to explain the reduced remanent polarization in ferroelectric field-effect transistors, and will be helpful for developing organic devices with a ferroelectric layer.

To understand the physical meaning of threshold voltage in organic field-effect transistors (OFETs), we studied the threshold voltage (shift) dependence on gate-insulator thickness as well as active-layer thickness, by using pentacene OFETs with and without a dipole interlayer between pentacene active layer and SiO2 gate insulator. Results showed that the presence of dipole monolayer caused a large threshold voltage shift and there was a linear relationship between the threshold voltage shift and the layer thickness of pentacene as well as SiO2. Assuming the pentacene film is a dielectric layer and the threshold voltage in pentacene OFET is determined from a zero-electric-field condition at the gate insulator interface, we propose a model based on compensation of the local electric field in the vicinity of semiconductor and gate insulator interface. The model well accounts for both the large negative threshold voltage shift and the linear relation. These findings reveal the importance of interfacial electric field for analyzing organic devices.

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