Yingli Chu

Ultrasensitive Photodetectors Based on Island-Structured CH3NH3PbI3 Thin Films

CH3NH3PbI3 perovskite-based optoelectronics have attracted intense research interests recently because of their easy fabrication process and high power conversion efficiency. Herein, we report a novel photodetector based on unique CH3NH3PbI3 perovskite films with island-structured morphology. The light-induced electronic properties of the photodetectors were investigated and compared to those devices based on conventional compact CH3NH3PbI3 films. The island-structured CH3NH3PbI3 photodetectors exhibited a rapid response speed (<50 ms), good stability at a temperature of up to 100 °C, a large photocurrent to dark current ratio (Ilight/Idark > 1 × 10(4) under an incident light of ∼6.59 mW/cm(2), and Ilight/Idark > 1 × 10(2) under low incident light ∼0.018 mW/cm(2)), and excellent reproducibility. Especially, the performance of the island-structured devices markedly exceed that of the conventional compact CH3NH3PbI3 thin-film devices. These excellent performances render the island-structured device to be potentially applicable for a wide range of optoelectronics.

Photosensitive and Flexible Organic Field-Effect Transistors Based on Interface Trapping Effect and Their Application in 2D Imaging Array

Flexible organic phototransistors are fabricated using polylactide (PLA), a polar biomaterial, as the dielectric material. The charge trapping effect induced by the polar groups of the PLA layer leads to a photosensitivity close to ≈104. The excellent performance of this new device design is further demonstrated by incorporating the phototransistors into a sensor array to successfully image a star pattern.

Facile Synthesis of a MoS2 and Functionalized Graphene Heterostructure for Enhanced Lithium-Storage Performance

A facile strategy was designed for the in situ synthesis of MoS2 nanospheres on functionalized graphene nanoplates (MoS2@f-graphene) for use as lithium-ion battery anode materials. A modified Birch reduction was used to exfoliate graphite into few-layer graphene followed by modification with functional groups. Compared to the most common approach of mixing MoS2 and reduced graphene oxide, our approach provides a way to circumvent the harsh oxidation and destruction of the carbon basal planes. In this process, alkylcarboxyl functional groups on the functionalized graphene (f-graphene) serve as sites where MoS2 nanospheres crystallize, and thus create bridges between the MoS2 nanospheres and the graphene layers to effectively facilitate electronic transport and to avoid both the aggregation of MoS2 and the restacking of graphene. As anode materials, this unique MoS2@f-graphene heterostructure has a high specific capacity of 1173 mAh g-1 at a current density of 100 mA g-1 and a good rate capacity (910 mAh g-1 at 1600 mA g-1).

High-Performance Inorganic Perovskite Quantum Dot–Organic Semiconductor Hybrid Phototransistors

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 Iphoto /Idark ratio. The devices exhibit outstanding optoelectronic properties in terms of photoresponsivity (1.7 × 104 A W-1 ), detectivity (2.0 × 1014 Jones), external quantum efficiency (67000%), Iphoto /Idark ratio (8.1 × 104 ), 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.

Preparation of Advanced CuO Nanowires/Functionalized Graphene Composite Anode Material for Lithium Ion Batteries

The copper oxide (CuO) nanowires/functionalized graphene (f-graphene) composite material was successfully composed by a one-pot synthesis method. The f-graphene synthesized through the Birch reduction chemistry method was modified with functional group “–(CH2)5COOH”, and the CuO nanowires (NWs) were well dispersed in the f-graphene sheets. When used as anode materials in lithium-ion batteries, the composite exhibited good cyclic stability and decent specific capacity of 677 mA·h·g−1 after 50 cycles. CuO NWs can enhance the lithium-ion storage of the composites while the f-graphene effectively resists the volume expansion of the CuO NWs during the galvanostatic charge/discharge cyclic process, and provide a conductive paths for charge transportation. The good electrochemical performance of the synthesized CuO/f-graphene composite suggests great potential of the composite materials for lithium-ion batteries anodes.

Pursuing Polymer Dielectric Interfacial Effect in Organic Transistors for Photosensing Performance Optimization

Abstract Polymer dielectrics in organic field‐effect transistors (OFETs) are essential to provide the devices with overall flexibility, stretchability, and printability and simultaneously introduce charge interaction on the interface with organic semiconductors (OSCs). The interfacial effect between various polymer dielectrics and OSCs significantly and intricately influences device performance. However, understanding of this effect is limited because the interface is buried and the interfacial charge interaction is difficult to stimulate and characterize. Here, this challenge is overcome by utilizing illumination to stimulate the interfacial effect in various OFETs and to characterize the responses of the effect by measuring photoinduced changes of the OFETs performances. This systemic investigation reveals the mechanism of the intricate interfacial effect in detail, and mathematically explains how the photosensitive OFETs characteristics are determined by parameters including polar group of the polymer dielectric and the OSC side chain. By utilizing this mechanism, performance of organic electronics can be precisely controlled and optimized. OFETs with strong interfacial effect can also show a signal additivity caused by repeated light pulses, which is applicable for photostimulated synapse emulator. Therefore, this work enlightens a detailed understanding on the interface effect and provides novel strategies for optimizing OFET photosensory performances.

Side-chain effect of organic semiconductors in OFET-based chemical sensors

Organic field-effect transistors (OFETs) offer great potential applications in chemical and biological sensing for homeland security, environmental monitoring, industry manufacturing, and medical/biological detection. Many studies concentrate on sensitivity and selectivity improvement of OFET-based sensors. We report four organic semiconductors with different alkyl side chain lengths but the same π-conjugated core structure for OFETs. Our work focuses on the molecular structure of organic semiconductors (OSCs). Alkyl side chains can hinder the diffusion of ammonia into the OSCs layer, which blocks the interaction between ammonia and conducting channel. The result also reveals the relationship between the alky chain and the film thickness in sensitivity control. These results are expected to be a guide to the molecular design of organic semiconductors and the choice of OSCs.摘要有机场效应晶体管在化学和生物传感、国土安全、环境监测、工业生产、医疗生物检测中具有很大的应用前景.如何提高基于有 机场效应晶体管传感器的灵敏度和选择性的研究已有很多报导. 本文用四种具有不同长度的烷基侧链和相同π–π共轭结构的有机半导体 来制备有机场效应晶体管, 集中研究有机半导体的分子结构. 烷基侧链可以减缓氨气在有机半导体层中的扩散, 阻止氨气和导电通道之间 的相互作用. 研究结果揭示了改变烷基侧链长度和薄膜厚度可以调控传感器的灵敏度, 这些结果有助于指导有机半导体材料的分子设计 和种类选择.

Direct Detection of Dilute Solid Chemicals with Responsive Lateral Organic Diodes

Organic field-effect transistors (OFETs) have emerged as promising sensors targeting chemical analytes in vapors and liquids. However, the direct detection of solid chemicals by OFETs has not been achieved. Here for the first time, we describe the direct detection of solid chemical analytes by organic electronics. An organic diode structure based on a horizontal side-by-side p-n junction was adopted and shown to be superior to OFETs for this purpose. The diodes showed more than 40% current decrease upon exposure to 1 ppm melamine powders. The estimated detection limit to melamine can potentially reach the ppb range. This is the first demonstration of an electronic signal from an interaction between a solid and an organic p-n junction directly, which suggests that our lateral organic diodes are excellent platforms for the development of future sensors when direct detection of solid chemicals is needed. The approach developed here is general and can be extended to chemical sensors targeting various analytes, opening unprecedented opportunities for the development of low-cost and high-performance solid chemical sensors.

Distinguishable Detection of Ultraviolet, Visible, and Infrared Spectrum with High-Responsivity Perovskite-Based Flexible Photosensors

Distinguishable detection of the ultraviolet, visible, and infrared spectrum is promising and significant for the super visual system of artificial intelligences. However, it is challenging to provide a photosensor with such broad spectral response ability. In this work, the ultraviolet, visible, and infrared spectrum is distinguished by developing serial photosensors based on perovskite/carbon nanotube hybrids. Oraganolead halide perovskites (CH3 NH3 PbX3 ) possess remarkable optoelectronic properties and tunable optical band gaps by changing the halogens, and integration with single-walled carbon nanotubes can further improve their photoresponsivities. The CH3 NH3 PbCl3 -based photosensor shows a responsivity up to 105 A W-1 to ultraviolet and no obvious response to visible light, which is superior to that of most ultraviolet sensors. The CH3 NH3 PbBr3 -based photosensor exhibits a high responsivity to visible light. Serial devices of the two hybrid photosensors with comparable electric and sensory performances can distinguish the spectrum of ultraviolet, visible, and infrared even with varying light intensities. The photosensors also demonstrate excellent mechanical flexibility and bending stability. By taking full advantages of the oraganolead halide perovskites, this work provides flexible high-responsivity photosensors specialized for ultraviolet, and gives a simple strategy for distinguishable detection of ultraviolet, visible, and infrared spectrum based on the serial flexible photosensors.

Performance improvement of organic phototransistors by using polystyrene microspheres

Organic phototransistors (OPTs) have been intensively studied in recent years due to the combined advantages of phototransistors and organic semiconductors (OSCs). However, the electrical performance of OPTs is largely limited by OSCs themselves, posing a challenge to further improve the performance of the devices. Preparing nano/micro-structures of OSCs is considered as an effective way to improve the performance of OPTs. Polystyrene (PS) microsphere, as a kind of insulating and low-cost material, is extensively used in fabricating nano/microporous structures, and the resulting devices exhibit high response to external stimuli. Therefore, we combined PS microspheres with OSCs to fabricate PS/OSC OPTs, and the Ilight/Idark ratio was enhanced by two orders of magnitude compared with the pristine counterparts, which can be modulated from 46 to 1800 by controlling the diameters of PS microspheres. This strategy paves a way for developing high-performance OPTs with nano/microporous structures with potential applications in organic optoelectronics.摘要有机光敏晶体管(OPTs)因结合了有机半导体和光敏晶体管的优势, 引起了科研工作者的广泛兴趣. 然而, OPTs性能很大程度上受限于有机半导体本身的性质, 这对进一步提高OPTs性能提出了挑战. 制备具有微纳结构的有机半导体被认为是提高器件性能的一种有效途径. 聚苯乙烯(PS)微球作为一种绝缘和低成本的材料, 可应用于制备微纳结构的器件, 使器件实现对外部刺激的超高响应. 本文中, 我们利用PS微球杂化有机半导体来制备具有微纳结构的OPTs, 使其光电流/暗电流(光灵敏度)提高了两个数量级, 并且通过调控PS微球的直径, 使光灵敏度从46增大到1800. 此研究结果为制备具有微纳孔结构的OPTs提供了新方法, 扩大了其在有机光电子中的应用.