Hybrid organic–inorganic perovskites have emerged as novel photovoltaic materials and hold great promise for realization of high-efficiency thin film solar modules. In this study, we unveil the ...ambipolar characteristics of perovskites by employing the transport measurement techniques of charge extraction by linearly increasing voltage (CELIV) and time-of-flight (TOF). These two complementary methods are combined to quantitatively determine the mobilities of hole and electron of CH3NH3PbI3 perovskite while revealing the recombination process and trap states. It is revealed that efficient and balanced transport is achieved in both CH3NH3PbI3 neat film and CH3NH3PbI3/PC61BM bilayer solar cells. Moreover, with the insertion of PC61BM, both hole and electron mobilities of CH3NH3PbI3 are doubled. This study offers a dynamic understanding of the operation of perovskite solar cells.
Suppressing the mobility of anionic species in polymer electrolytes (PEs) is essential for mitigating the concentration gradient and internal cell polarization, and thereby improving the stability ...and cycle life of rechargeable alkali metal batteries. Now, an ether‐functionalized anion (EFA) is used as a counter‐charge in a lithium salt. As the salt component in PEs, it achieves low anionic diffusivity but sufficient Li‐ion conductivity. The ethylene oxide unit in EFA endows nanosized self‐agglomeration of anions and trapping interactions between the anions and its structurally homologous matrix, poly(ethylene oxide), thus suppressing the mobility of negative charges. In contrast to previous strategies of using anion traps or tethering anions to a polymer/inorganic backbone, this work offers a facile and elegant methodology on accessing selective and efficient Li‐ion transport in PEs and related electrolyte materials (for example, composites and hybrid electrolytes).
The right counter‐charge: An ether‐functionalized anion (EFA) as counter‐charge to a lithium ion could achieve low anionic diffusivity but sufficient Li‐ion conductivity in a polymer electrolyte. This feature is highly desired in high‐performance solid‐state lithium batteries.
A novel ladder‐type donor (IDTT) is developed by substituting the two outward thiophenes of the IDT donor with two thieno3,2‐bthiophenes. The polymer derived from this donor possesses longer ...effective conjugation and better planarity, which improves electron delocalization along the polymer backbone and charge mobility. The polymer solar cell device using PIDTT‐DFBT shows a high power conversion efficiency of 7.03% with a large open‐circuit voltage of 0.95 V without using any additives or post‐solvent/thermal annealing processes.
Solution processable semiconducting polymers with excellent film forming capacity and mechanical flexibility are considered among the most progressive alternatives to conventional inorganic ...semiconductors. However, the random packing of polymer chains and the disorder of the polymer matrix typically result in low charge transport mobilities (10–5–10–2 cm2 V–1 s–1). These low mobilities compromise their performance and development. Here, we present a strategy, by utilizing capillary action, to mediate polymer chain self-assembly and unidirectional alignment on nanogrooved substrates. We designed a sandwich tunnel system separated by functionalized glass spacers to induce capillary action for controlling the polymer nanostructure, crystallinity, and charge transport. Using capillary action, we demonstrate saturation mobilities with average values of 21.3 and 18.5 cm2 V–1 s–1 on two different semiconducting polymers at a transistor channel length of 80 μm. These values are limited by the source-drain contact resistance, R c. Using a longer channel length of 140 μm where the contact resistance is less important, we measured μh = 36.3 cm2 v–1 s–1. Extrapolating to infinite channel length where R c is unimportant, the intrinsic mobility for poly4-(4,4-dihexadecyl-4H-cyclopenta1,2-b:5,4-b′dithiophen-2-yl)-alt-1,2,5thiadiazolo3,4-cpyridine (M n = 140 kDa) at this degree of chain alignment and structural order is μh ≈ 47 cm2 v–1 s–1. Our results create a promising pathway toward high performance, solution processable, and low-cost organic electronics.
The diffusion coefficient is independent of defect density. Improving carrier lifetime is an effective way to increase carrier diffusion length.
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Linear conjugated polymers have attracted significant attention in organic electronics in recent decades. However, despite intrachain π‐delocalization, interchain hopping is their transport ...bottleneck. In contrast, two‐dimensional (2D) conjugated polymers, as represented by 2D π‐conjugated covalent organic frameworks (2D c‐COFs), can provide multiple conjugated strands to enhance the delocalization of charge carriers in space. Herein, we demonstrate the first example of thiophene‐based 2D poly(arylene vinylene)s (PAVs, 2DPAV‐BDT‐BT and 2DPAV‐BDT‐BP, BDT=benzodithiophene, BT=bithiophene, BP=biphenyl) via Knoevenagel polycondensation. Compared with 2DPAV‐BDT‐BP, the fully thiophene‐based 2DPAV‐BDT‐BT exhibits enhanced planarity and π‐delocalization with a small band gap (1.62 eV) and large electronic band dispersion, as revealed by the optical absorption and density functional calculations. Remarkably, temperature‐dependent terahertz spectroscopy discloses a unique band‐like transport and outstanding room‐temperature charge mobility for 2DPAV‐BDT‐BT (65 cm2 V−1 s−1), which far exceeds that of the linear PAVs, 2DPAV‐BDT‐BP, and the reported 2D c‐COFs in the powder form. This work highlights the great potential of thiophene‐based 2D PAVs as candidates for high‐performance opto‐electronics.
Crystalline, planar and fully thiophene‐based two‐dimensional poly(arylene vinylene) is developed for the first time via Knoevenagel polycondensation. It exhibits a narrow optical band gap and efficient π‐delocalization for band‐like transport and high charge carrier mobility.
A large database of known molecular semiconductors is used to define a plausible physical limit to the charge carrier mobility achievable within this materials class. From a detailed study of the ...desirable properties in a large dataset, it is possible to establish whether such properties can be optimized independently and what would be a reasonably achievable optimum for each of them. All relevant parameters are computed from a set of almost five thousand known molecular semiconductors, finding that the best known materials are not ideal with respect to all properties. These parameters in decreasing order of importance are the molecular area, the nonlocal electron–phonon coupling, the 2D nature of transport, the local electron–phonon coupling, and the highest transfer integral. It is also found that the key properties related to the charge transport are either uncorrelated or “constructively” correlated (i.e., they improve together) concluding that a tenfold increase in mobility is within reach in a statistical sense, on the basis of the available data. It is demonstrated that high throughput screenings, when coupled with physical models of transport produce both specific target materials and a more general physical understanding of the materials space.
The physical parameters relevant for charge transport are evaluated for ≈5000 known molecular semiconductors extracted from the Cambridge Structural Database and the expected charge mobility is computed. A number of potential high mobility semiconductors are found and, by studying the distribution of such parameters, the physical limit to the charge mobility achievable within this materials class is predicted.
One of the most important issues of the organic light‐emitting diode (OLED) is the highly efficient blue‐emissive material, which demands both excellent photoluminescent quantum yield (PLQY) and ...balanced carrier mobilities. Herein, a series of blue‐emissive donor–π–acceptor (D–π–A) materials with fluorene π‐bridge and their D–A analogues are synthesized and discovered with a theoretical combined experimental method. Based on the excellent electron mobility of the oxadiazole (OXZ) acceptor, it is further proven that the insertion of the fluorene π‐bridge can not only contribute to the formation of hybrid local and charge‐transfer excited state with high PLQY, but also give rise to the hole mobilities by enhanced intermolecular face‐to‐face stacking. As a result, the non‐doped OLED of TPACFOXZ exhibits a high maximum external quantum efficiency approaching 10% with boosted and balanced hole and electron mobilities of 5.60 × 10−5 and 6.60 × 10−5 cm2 V−1 s−1, respectively, which are among the best results of the non‐doped blue fluorescent OLEDs.
Incorporation of fluorene‐bridge in donor–acceptor (D–A) molecules is proven to demonstrates double functions: high photoluminescent quantum yield and balanced carrier mobilities due to decent stacking patterns. Remarkably, the non‐doped OLED of the fluorene‐bridged D–A materials demonstrate excellent electroluminescent performances with high efficiency, low driving voltage, low rolling‐off with boosted and balanced carrier mobility.
•Understanding graphene structure and properties can help in grasping the idea of graphene in suitable consideration and applications.•Integration of graphene in fuel cells and batteries have shown a ...better enhancement in the performance and efficiency.•Developing further advanced studies and researches on graphene can be a potential material in renewable energy sector.•Overcoming the main challenges of graphene materials will make it the best candidate for any application especially in energy field.
Energy demand is increasing in the present world where it is essential to explore alternative energy resource that is clean, renewable and sustainable. Graphene is now receiving the great attention as it possesses excellent properties such as high charge mobility up to 230,000 cm2/Vs, 3000 W/m.K thermal conductivity, 2.3% absorption of visible light, strong mechanical strength of 130 GPa and high specific surface area of 2600 m2/g. These properties can be altered depending on synthesis techniques to obtain graphene such as; mechanical exfoliation, reduction of graphene oxide, chemical vapour deposition (CVD) and epitaxial growth of graphene. Furthermore, different characteristics of graphene can be employed for different applications in energy conversion and storage, for example, fuel cell and lithium ion battery. Hence, many studies were investigated to examine graphene and its applications. The objectives of this review is to understand and cover graphene background including properties and synthesis, which will help in understanding better the concept of graphene in its application such as in fuel cell and lithium ion batteries. In addition, it is showing the most key challenges and future consideration when nanostructured graphene is utilized.
Boron nitride's (BN) large band gap does not permit carrier transport at ambient conditions. We show that BN sheets can be exfoliated by functionalization with oxy-groups to introduce additional ...acceptor and donor energy levels appropriate for energy storage devices. Further, the incorporation of heteroatoms into transition metal sulfides enhances capacitance via Faradic redox reactions and their cyclic stability. The functionalized boron nitride (mK-BN) and Carbon Nanotubes (CNTs) are intertwined with a Zn-doped Cadmium-Sulfide (Zn–CdS) nanostructure to increase the surface area-charge storage. In a supercapacitor application, Zn–CdS/mK-BN/CNT exhibits a 787 F/g specific capacitance (SC) in an aqueous (aq.) electrolyte. Further, the Zn–CdS/mK-BN/CNT was deployed as a cathode material in an asymmetric supercapacitor device (ASC) coupled with an ionic electrolyte (IE), (NHEt3)+(NO3)−, offered a SC of 173 F/g with an approximate 99% stability due to the enhanced charge mobility. The reported functionalization of BN induces additional energy levels making the material ideal for energy storage devices and will directly impact the next-generation of advanced supercapacitor electrode materials.
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