[2017.05] 张业栋同学的论文"Precise Patterning of Organic Single Crystals via Capillary-Assisted Alternating-Electric Field "发表在 small上
Owing to the extraordinary properties, organic micro/nanocrystals are important building blocks for future low-cost and high-performance organic electronic devices. However, integrated device application of the organic micro/nanocrystals is hampered by the difficulty in high-throughput, high-precision patterning of the micro/nanocrystals. In this study, the authors demonstrate, for the first time, a facile capillary-assisted alternating-electric field method for the large-scale assembling and patterning of both 0D and 1D organic crystals. These crystals can be precisely patterned at the photolithography defined holes/channels at the substrate with the yield up to 95% in 1 mm2. The mechanism of assembly kinetics is systematically studied by the electric field distribution simulation and experimental investigations. By using the strategy, various organic micro/nanocrystal patterns are obtained by simply altering the geometries of the photoresist patterns on substrates. Moreover, ultraviolet photodetectors based on the patterned Alq3 micro/nanocrystals exhibit visible–blind photoresponse with high sensitivity as well as excellent stability and reproducibility. This work paves the way toward high-integration, high-performance organic electronic, and optoelectronic devices from the organic micro/nanocrystals.
[2017.02] 邓巍同学的论文"Ultrahigh-Responsivity Photodetectors from Perovskite Nanowire Arrays for Sequentially Tunable Spectral Measurement"发表在 Nano Lett. 上
Compared with polycrystalline films, single-crystalline methylammonium lead halide (MAPbX3, X = halogen) perovskite nanowires (NWs) with well-defined structure possess superior optoelectronic properties for optoelectronic applications. However, most of the prepared perovskite NWs exhibit properties below expectations due to poor crystalline quality and rough surfaces. It also remains a challenge to achieve aligned growth of single-crystalline perovskite NWs for integrated device applications. Here, we report a facile fluid-guided antisolvent vapor-assisted crystallization (FGAVC) method for large-scale fabrication of high-quality single-crystalline MAPb(I1-xBrx)3 (x = 0, 0.1, 0.2, 0.3, 0.4) NW arrays. The resultant perovskite NWs showed smooth surfaces due to slow crystallization process and moisture-isolated growth environment. Significantly, photodetectors made from the NW arrays exhibited outstanding performance in respect of ultrahigh responsivity of 12 500 A W-1, broad linear dynamic rang (LDR) of 150 dB, and robust stability. The responsivity represents the best value ever reported for perovskite-based photodetectors. Moreover, the spectral response of the MAPb(I1-xBrx)3 NW arrays could be sequentially tuned by varying the content of x = 0-0.4. On the basis of this feature, the NW arrays were monolithically integrated to form a unique system for directly measuring light wavelength. Our work would open a new avenue for the fabrication of high-performance, integrated optoelectronic devices from the perovskite NW arrays.
[2017.02] 课题组应邀为 Adv. Mater. Tech. 撰写了题为"Ordered and Patterned Assembly of Organic Micro/Nanocrystals for Flexible Electronic and Optoelectronic Devices"的综述
Organic semiconductor micro/nanocrystals (OSMCs) have attracted intensive research over the past few decades. Their unique electrical and mechanical properties afford them applications in a vast network of active flexible electronic and optoelectronic fields, such as organic field-effect transistors (OFETs), photodetectors (PDs), and organic light-emitting diodes (OLEDs) etc. However, the growth orientation and location of OSMCs are usually stochastic in nature, which hinders the further use of OSMCs in large-area plastic electronic devices. On the other hand, traditional microelectronic processing techniques like photolithography may damage the plastic substrates, polymer insulators, and organic materials. Thus the alignment and patterning of OSMCs and development of new device construction technologies are prerequisite for their flexible device applications in practice. In this progress report, we will highlight the important advancement for fabricating the aligned and patterned OSMCs, with a focus on their applications in next-generation flexible electronic and optoelectronic devices. Also, the challenges and outlooks of the ordered and patterned OSMCs in the flexible device applications are presented.
[2017.01] 刁森林同学的论文"12.35% efficient graphene quantum dots/silicon heterojunction solar cells using graphene transparent electrode"发表在 Nano Energy 上
Zero-dimensional graphene quantum dots (GQDs) have lately intrigued intensive interest because of their great promise in energy, optoelectronic, and bio-imaging applications. Herein, we demonstrated the fabrication of highly efficient GQDs/n-silicon heterojunction solar cells via a simple solution process. Owing to the unique band structure, the GQDs layer could not only serve as hole transport layer to facilitate the separation of photo- generated electron-hole pairs, but also act as electron blocking layer to suppress the carrier recombination at anode. Moreover, graphene was used as the transparent top electrode for the heterojunction solar cells, ensuring the efficient light absorption and carrier collection. By adjusting the sizes of GQDs and the thickness of GQDs layer, a power conversion efficiency (PCE) as high as 12.35% under AM 1.5G irradiation was achieved, which represented a new efficiency record for this new-type solar cell. The devices also exhibited excellent stability in air due to the high chemical/physical stability of GQDs and graphene. The successful achievement of the high- efficiency GQDs/Si heterojunction solar cells opens up the opportunities for their potential applications in high- performance and low-cost photovoltaics.
[2016.12] 夏斐斐老师的论文"Surface Charge Transfer Doping via Transition Metal Oxides for Efficient p-Type Doping of II-VI Nanostructures"发表在 ACS Nano 上
Wide band gap II–VI nanostructures are important building blocks for new-generation electronic and optoelectronic devices. However, the difficulty of realizing p-type conductivity in these materials via conventional doping methods has severely handicapped the fabrication of p–n homojunctions and complementary circuits, which are the fundamental components for high-performance devices. Herein, by using first-principles density functional theory calculations, we demonstrated a simple yet efficient way to achieve controlled p-type doping on II–VI nanostructures via surface charge transfer doping (SCTD) using high work function transition metal oxides such as MoO3, WO3, CrO3, and V2O5 as dopants. Our calculations revealed that these oxides were capable of drawing electrons from II–VI nanostructures, leading to accumulation of positive charges (holes injection) in the II–VI nanostructures. As a result, Fermi levels of the II–VI nanostructures were shifted toward the valence band regions after surface modifications, along with the large enhancement of work functions. In situ ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy characterizations verified the significant interfacial charge transfer between II–VI nanostructures and surface dopants. Both theoretical calculations and electrical transfer measurements on the II–VI nanostructure-based field-effect transistors clearly showed the p-type conductivity of the nanostructures after surface modifications. Strikingly, II–VI nanowires could undergo semiconductor-to-metal transition by further increasing the SCTD level. SCTD offers the possibility to create a variety of electronic and optoelectronic devices from the II–VI nanostructures via realization of complementary doping.
[2016.12] 综述"Surface Charge Transfer Doping of Low-Dimensional Nanostructures toward High-Performance Nanodevices"以封面论文的形式发表在 Adv. Mater. 上.
Device applications of low-dimensional semiconductor nanostructures rely on the ability to rationally tune their electronic properties. However, the conven- tional doping method by introducing impurities into the nanostructures suf- fers from the low ef ciency, poor reliability, and damage to the host lattices. Alternatively, surface charge transfer doping (SCTD) is emerging as a simple yet ef cient technique to achieve reliable doping in a nondestructive manner, which can modulate the carrier concentration by injecting or extracting the carrier charges between the surface dopant and semiconductor due to the work-function difference. SCTD is particularly useful for low-dimensional nanostructures that possess high surface area and single-crystalline struc- ture. The high reproducibility, as well as the high spatial selectivity, makes SCTD a promising technique to construct high-performance nanodevices based on low-dimensional nanostructures. Here, recent advances of SCTD are summarized systematically and critically, focusing on its potential applica- tions in one- and two-dimensional nanostructures. Mechanisms as well as characterization techniques for the surface charge transfer are analyzed. We also highlight the progress in the construction of novel nanoelectronic and nano-optoelectronic devices via SCTD. Finally, the challenges and future research opportunities of the SCTD method are prospected.
[2016.08] 商其勋同学的论文被《Materials Views》亮点报道
[2016.08] 商其勋同学的论文"An Inherent Multifunctional Sellotape Substrate for High‐Performance Flexible and Wearable Organic Single‐Crystal Nanowire Array‐Based Transistors"发表在 Adv. Electron. Mater. 上
Sellotape, as a flexible, sticky, and lightweight substrate, can be integrated in electronic devices to realize unprecedented and low-cost applications, such as biomedical devices, wearable electronics, smart clothes, and sensory skin for robotic system. However, very few works have successfully demonstrated fabricating devices on sellotape substrates, primarily because traditional microelectronic processing techniques, including photolithography, metalliza- tion, and lift-off, are incompatible with sellotape. Here a novel tape-stripping method is demonstrated for large-area fabrication of high-performance flexible and wearable organic nanowire array-based field-effect transistors (ONWFETs) on sellotape substrates. The copper phthalocyanine ONWFETs on the tapes exhibit high average mobility (≈1.02 cm2 V−1 s−1) as well as high bending and wearing stability. Furthermore, 3D ONWFET circuitry consisting of five vertically stacked layers is demonstrated. Device geometries and elec- tronic properties are maintained with high fidelity after sequential stacking processes. This is so far the first study of ONWFETs on flexible tapes and their applications in wearable or 3D integrated devices. It is anticipated that the novel tape stripping method may help overcome upcoming difficulties for organic flexible electronics.
[2016.08] 邓巍同学的论文被 《X-MOL》 报道
[2016.07] 毛杰同学的论文被《Materials Views》亮点报道
[2016.04] 张洪宾老师的论文"High-Responsivity, High-Detectivity, Ultrafast Topological Insulator Bi2Se3 /Silicon Heterostructure Broadband Photodetectors"发表在 ACS Nano 上
As an exotic state of quantum matter, topological insulators have promising applications in new-generation electronic and optoelectronic devices. The realization of these applications relies critically on the preparation and properties understanding of high-quality topological insulators, which however are mainly fabricated by high-cost methods like molecular beam epitaxy. We here report the successful preparation of high-quality topological insulator Bi2Se3/Si heterostructure having an atomically abrupt interface by van der Waals epitaxy growth of Bi2Se3 films on Si wafer. A simple, low-cost physical vapor deposition (PVD) method was employed to achieve the growth of the Bi2Se3 films. The Bi2Se3/Si heterostructure exhibited excellent diode characteristics with a pronounced photoresponse under light illumination. The built-in potential at the Bi2Se3/Si interface greatly facilitated the separation and transport of photogenerated carriers, enabling the photodetector to have a high light responsivity of 24.28 A W–1, a high detectivity of 4.39 × 1012 Jones (Jones = cm Hz1/2 W–1), and a fast response speed of aproximately microseconds. These device parameters represent the highest values for topological insulator-based photodetectors. Additionally, the photodetector possessed broadband detection ranging from ultraviolet to optical telecommunication wavelengths. Given the simple device architecture and compatibility with silicon technology, the topological insulator Bi2Se3/Si heterostructure holds great promise for high-performance electronic and optoelectronic applications.
[2016.04] 邓巍同学的论文"Organometal Halide Perovskite Quantum Dots Light-Emitting Diodes"发表在 Adv. Funct. Mater. 上
Organometal halide perovskites quantum dots (OHP-QDs) with bright, color-tunable, and narrow-band photoluminescence have significant advantages in display, lighting, and laser applications. Due to sparse concentrations and difficulties in the enrichment of OHP-QDs, production of large-area uniform films of OHP-QDs is a challenging task, which largely impedes their use in electroluminescence (EL) devices. Here, we report a simple dip-coating method to effectively fabricate large-area uniform films of OHP-QDs. Using this technique, we successfully produced multicolor OHP-QDs light-emitting diodes (OQ-LEDs) emitting in blue, blue-green, green, orange, and red color by simply tuning the halide composition or size of QDs. The blue, green and red OQ-LEDs exhibited, respectively, a maximum luminance of 2673, 2398, and 986 cd m-2 at a current efficiency of 4.01, 3.72, and 1.52 cd A-1, and an external quantum efficiency of 1.38%, 1.06%, and 0.53%, which are much better than most LEDs based on OHP films. The packaged OQ-LEDs show long-term stability in air (humidity~50%) for at least 7 days. The results demonstrate the great potential of the dip-coating method to fabricate large-area uniform films for various QDs. The high-efficiency OQ-LEDs also demonstrate the promising potential of OHP-QDs for low-cost display, lighting and optical communication applications.
[2016.03] 毛杰同学的论文"Ultrafast, Broadband Photodetector Based on MoSe2/Silicon Heterojunction with Vertically Standing Layered Structure Using Graphene as Transparent Electrode"发表在 Adv. Sci. 上
Advances in the photocurrent conversion of layered molybdenum diselenide (MoSe2)
have enabled the realization of a variety of important optoelectronic devices such as
photovoltaics and photodetectors owing to its extraordinary properties. However,
photodetectors based on MoSe2 mono-/multilayer sheets still suffer from low response
speed and relatively weak light response arising from low light absorption. Herein, it is
demonstrated that high-quality MoSe2/Si heterojunctions could be constructed by
depositing n-type MoSe2 film on p-type Si substrate. The relatively thick MoSe2 film
could offer strong light absorption from ultraviolet (UV) to visible and to near-infrared
(NIR) light. Significantly, the MoSe2 film fabricated by sputtering possessed a vertically
standing layered structure, greatly facilitating the separation and transport of
photogenerated carriers. Collection of the carriers was further enhanced by the use of
graphene (Gr) transparent electrode on the top. Owing to the unique device structure,
the Gr/MoSe2/Si photodetectors exhibited outstanding device characteristics in terms
of broadband response ranging from 365 to 1310 nm, high detectivity of 7.13 × 10^10
Jones, and ultrafast response speed of 270 ns. These parameters are significantly
better than mono-/multilayer MoSe2-based photodetectors. Our work paves the way for
development of high-performance optoelectronic devices based on MoSe2/Si
[2016.03] 邓巍同学的论文"Aligned Single-Crystalline Perovskite Microwire Arrays for High-Performance Flexible Image Sensors with Long-Term Stability"发表在 Adv. Mater. 上
A simple, low-cost blade-coating method is developed for the large-area fabrication of single-crystalline aligned CH3NH3PbI3 microwire (MW) arrays. The solution-coating method is applicable to flexible substrates, enabling the fabrication of MW-array-based photodetectors with excellent long-term stability, flexibility, and bending durability. Integrated devices from such photodetectors demonstrate high performance for high-resolution, flexible image sensors.
[2016.01] 综述"Two-dimensional layered material/silicon heterojunctions for energy and optoelectronic applications"发表在 Nano Res. 上
As one of the most important semiconductor materials, silicon (Si) has been widely used in current energy and optoelectronic devices, such as solar cells and photodetectors. However, the traditional Si p–n junction solar cells need complicated fabrication processes, leading to the high cost of Si photovoltaic devices. The wide applications of Si-based photodetectors are also hampered by their low sensitivity to ultraviolet and infrared light. Recently, two-dimensional (2D) layered materials have emerged as a new material system with tremendous potential for future energy and optoelectronic applications. The combination of Si with 2D layered materials represents an innovative approach to construct high-performance optoelectronic devices by harnessing the complementary advantages of both materials. In this review, we summarize the recent advances in 2D layered material/Si heterojunctions and their applications in photovoltaic and optoelectronic devices. Finally, the outlook and challenges of 2D layered material/Si heterojunctions for high-performance device applications are presented.