Advanced Electronic Materials

An cross‐bar structure is employed to design a transparent p‐n junction‐based photodetector. The device consisting of aligned n‐SnO₂ and p‐NiO nanofibers is prepared via a mature electrospinning process that is suitable for commercial applications. It exhibits a high detectivity of 2.33 × 10¹³ Jones under 250 nm illumination at −5 V, outperforming most state‐of‐art SnO₂‐based UV photodetectors. It is also endowed with a self‐powered feature due to a photovoltaic effect from the p‐n junction, resulting in a photocurrent of 10⁻¹⁰ A, responsivity of 30.29 mA W⁻¹ at 0 V bias, and detectivity of 2.24 × 10¹¹ Jones at 0.05 V bias. Moreover, the device is highly transparent (over 90% toward visible light) due to the wide band gap of photoactive materials and well‐designed cross‐bar fiber structure. Additionally, an n‐SnO₂‐p‐ZnO:Ag (Ag doped ZnO) self‐powered UV photodetector is fabricated that shows good performance and give another example of the use of the cross‐bar structure.

Sự phát triển nhanh chóng của các công nghệ hữu cơ mới đã dẫn đến những ứng dụng quan trọng của thiết bị điện tử hữu cơ như đi-ốt phát sáng, pin năng lượng mặt trời và bóng bán dẫn hiệu ứng trường. Yêu cầu lớn hiện nay là chất dẫn điện có độ dẫn cao và tính trong suốt để có thể hoạt động như lớp chuyển tải điện tích hoặc kết nối điện trong các thiết bị hữu cơ. Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS), được biết đến như là chất dẫn điện nổi bật nhất, đã đảm nhận vai trò này nhờ vào khả năng tạo màng tốt, tính trong suốt cao, độ dẫn điện điều chỉnh được và độ ổn định nhiệt tuyệt vời. Bài tổng quan này tóm tắt các phương pháp hóa học và vật lý thú vị có thể nâng cao hiệu quả độ dẫn điện của PEDOT:PSS một cách hiệu quả, đặc biệt tập trung vào cơ chế nâng cao độ dẫn cũng như ứng dụng của các màng PEDOT:PSS. Những triển vọng cho các nỗ lực nghiên cứu trong tương lai cũng được đề cập. Dự kiến rằng các màng PEDOT:PSS với độ dẫn cao và tính trong suốt có thể là trọng điểm cho những đột phá vật liệu điện tử hữu cơ trong tương lai.

Bismuth ferrite (BFO)‐based ceramics with large electromechanical response are important in electronic device applications. To better understand their physical mechanisms, a new phase diagram established by temperature dependence of dielectric properties, temperature dependence of piezoelectric coefficient, and the evolution of their properties is proposed to explain the contribution of piezoelectric and strain response by comparing ferroelectric (FE) and relaxor ferroelectric (RFE) compositions. The FE components with macrodomains have large piezoelectric constant (d₃₃ of 412 pC/N) at high temperature. The RFE components with nanodomains possess giant strain response (S_uni = 0.37%) at 180 °C. Combined with in situ and ex situ techniques, the physical mechanisms behind the enhancement of these properties are explored. Macrodomains and multipolar phase coexistence contribute to the piezoelectricity improvement. Nanodomains and an unstable depolarization temperature (T_d) region engineer the strain enhancement, which can promote electric‐field‐induced domain switching, lattice strain, and irreversible phase transition. In particular, the T_d region of BiFeO₃‐based ceramics has been ignored for several years, although it is actually an effective medium to engineer properties. The proposed phase diagram and dynamic model can be used to well understand the structural origins of large electromechanical properties in BFO‐based ceramics, which can give some guidance to explore materials with excellent properties for different applications.

Poly(3,4‐ethylenedioxy thiophene):poly(styrenesulfonate) (PEDOT:PSS) exhibits valuable characteristics concerning stability, green‐processing, flexibility, high electrical conductivity, and ease of property modulation, qualifying it as one of the most promising p‐type organic conductors for thermoelectric (TE) applications. While blending with inorganic counterparts is considered a good strategy to further improve polymeric TE properties, only a few attempts succeed so far due to inhomogeneous embedding and the non‐ideal organic‐inorganic contact. Here a new strategy to include nanoparticles (NPs) without any ligand termination inside PEDOT:PSS thin films is proposed. Spark discharge‐generated tin oxide NPs (SnO_x‐NPs) are “gently” and homogenously deposited through low‐energy diffusion mode. Strong interaction between naked SnO_x‐NPs and PSS chains occurs in the topmost layer, causing a structural reorganization towards an improved PEDOT chains crystalline packing at the bottom, providing a positive contribution to the electrical conductivity. Meanwhile, dedoping and energy filtering effect introduced by the SnO_x‐NPs cause dramatic Seebeck coefficient enhancement. The optimized power factor of 116 μWm⁻¹ K⁻² achieved is more than six times higher than the value found for the film without NPs. This easy and efficient strategy promises well for future mass production of flexible TE devices and the mechanism revealed may inspire future research on TEs and flexible electronics.

Advances in organic thermoelectric materials have focused on the enhancement of mechanical property to address the limitations and needs of forming flexible and free‐standing films for the application of flexible/wearable thermoelectric devices. Herein, thermoelectric nanocomposite films are fabricated based on conductive polymer poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), plastic reinforcer polyvinyl alcohol (PVA), and inorganic Bi_0.5Sb_1.5Te₃ thermoelectric nanocrystals with various contents. The resulting PEDOT:PSS/PVA/Bi_0.5Sb_1.5Te₃ nanocomposite films exhibit a power factor of 47.7 µW m⁻¹ K⁻² and a ZT value of 0.05 at 300 K. More importantly, they are mechanically tough, yet very flexible with a tensile strength of 79.3 MPa and a fracture strain of 32.4%, which is sufficient to meet the required mechanical properties of textile manufacturing and body movements for flexible thermoelectric films, thus providing a substantial impact on future developments of flexible/wearable energy generation devices.

In order to develop functional nanostructures with controllable size, composition, morphology, and interface, a series of dopamine (DA) modified polypyrrole (PPy) nanostructures that have tunable electrical conductivity and improved water dispersibility are prepared. The DA‐PPy nanostructures exhibit various morphologies, including nanosphere, nanofiber, nanorod, and nanoflake; and all of these nanostructures can be achieved by simply varying the DA/Py reacting mole ratio. Furthermore, the potential application of each as‐fabricated DA‐PPy, which depend on their tunable electrical properties, are explored. In particular, DA‐PPy resulting from a 0.032 dopamine/pyrrole (DA/Py) mole ratio demonstrate superior capacitance for supercapacitors; at DA/Py = 0.064, DA‐PPy can be implemented as a co‐filler into the epoxy network to prepare hybrid electrically conductive adhesives and DA‐PPy synthesized from 0.64 DA/Py mole ratio reveals impressive electromagnetic microwave absorption ability that can be used for electromagnetic interference shielding applications. Due to the synergetic effects of DA and electrically conductive polymer PPy, this one‐step procedure represents a promising protocol to control the syntheses and properties of nanomaterials for applications in advanced electronic devices.

Superior photovoltaic performance in organic–inorganic hybrid perovskite is based on the unique properties of each moiety contined within it. Identifying the role of metal atoms in the perovskite is of great importance to explore the low‐toxicity lead‐free perovskite solar cells. By using the first‐principle calculations, four types of AMX₃ (A = CH₃NH₃, M = Pb, Sn, Ge, Sr, X = I) perovskite materials are investigated and an attempt is made to understand the structural and electronic influences of the metal atoms on the properties of perovskites. Then, the solutions to the replacement of Pb are discussed. It is found that for the small radius metal atoms as compared with Pb, the strong geometry distortion will result in a less p–p electron transition and larger carrier effective mass. The outer ns² electrons of the metal ions play critical roles on the modulation of the optical and electronic properties for perovskite materials. These findings suggest that the solutions to the Pb replacement might be metal or metallic clusters that have effective ionic radius and outer ns² electrons configuration on the metal ions with low ionization energy similar to Pb²⁺. Based on this, lead‐free perovskite solar cells are expected to be realized in the near future.

Antiferroelectric ceramics with extraordinary energy‐storage density have gained exponentially soaring attention for their applications in pulsed power capacitors. Nevertheless, high energy dissipation is a deficiency of antiferroelectric materials. The modulation of Ba/La‐doped (Pb_0.91Ba_xLa_0.06−2x/3)(Zr_0.6Sn_0.4)O₃ (x = 0.015, 0.03, 0.045, 0.06) antiferroelectric ceramics is aimed at increasing the energy efficiency and obtaining an ideal energy storage density. The traditional solid‐state reaction is exploited for ceramics fabrication and all prepared samples exhibit an ultralow electrical hysteresis due to the local structural heterogeneity, as verified by Raman spectroscopy. Of particular importance is the fact that the (Pb_0.91Ba_0.045La_0.03)(Zr_0.6Sn_0.4)O₃ ceramic possesses an excellent recoverable energy storage density (W_rec = 8.16 J cm⁻³) and a remarkable energy efficiency (η = 92.1%) simultaneously under an electric field of 340 kV cm⁻¹. Moreover, the corresponding ceramic exhibits a superior discharge current density (C_D = 1498.6 A cm⁻²), a high level of power density (P_D = 202.3 MW cm⁻³), and a nanosecond‐level discharge period (53 ns). This provides a promising antiferroelectric material for fabricating ceramic capacitors with excellent energy storage and high power characteristics.

Silicon doped hafnium oxide was the material used in the original report of ferroelectricity in hafnia in 2011. Since then, it has been subject of many further publications including the demonstration of the world's first ferroelectric field‐effect transistor in the state‐of‐the‐art 28 nm technology. Though many studies are conducted with a strong focus on application in memory devices, a comprehensive study on structural stability in these films remains to be seen. In this work, a film thickness of about 36 nm, instead of the 10 nm used in most previous studies, is utilized to carefully probe how the concentration range impacts the evolution of phases, the dopant distribution, the field cycling effects, and their interplay in the macroscopic ferroelectric response of the films. Si:HfO₂ appears to be a rather fragile system: different phases seem close in energy and the system is thus rich in competing phenomena. Nonetheless, it offers ferroelectricity or field‐induced ferroelectricity for elevated annealing conditions up to 1000 °C. Similar to the measures taken for conventional ferroelectrics such as lead zirconate titanate, engineering efforts to guarantee stable interfaces and stoichiometry are mandatory to achieve stable performance in applications such as ferroelectric memories, supercapacitors, or energy harvesting devices.