A highly efficient simplified organic light-emitting diode (OLED) with a molecularly controlled strategy to form near-perfect interfacial layer on top of the anode is demonstrated. A self-organized polymeric hole injection layer (HIL) is exploited increasing hole injection, electron blocking, and reducing exciton quenching near the electrode or conducting polymers; this HIL allows simplified OLED comprised a single small-molecule fluorescent layer to exhibits a high current efficiency (∼20 cd/A).

mesoporous charge transfer layer, their application into the fl exible electronics would be limited due to their brittleness and the high-temperature (i.e., T > 450 °C) sintering process which damages plastic substrates. Otherwise, solutionprocessed planar heterojunction (SP-PHJ) PrSCs can be fabricated using low-temperature processable interlayers without mesoporous metal oxides; this approach enables the fabrication of fl exible PrSCs on plastic substrates. [7][8][9] Therefore, the development of a solution-processed and effi ciently charge-transporting interlayer material has been required recently to increase PCE of SP-PHJ PrSCs for the practical application of highly effi cient and fl exible PrSCs. In addition to conducting polymers (e.g., poly(3,4-ethylen edioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), [ 7,9,15,16 ] self-organized hole extraction layer (SOHEL) [ 9 ] ), several different hole transport materials (HTMs), including inorganic materials (graphene oxide, [ 17 ] reduced graphene oxide, [ 18 ] NiO x [ 15 ] ) and conjugated polymers (e.g., PolyTPD, [ 19 ] P3HT, [ 20 ] poly(2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2′,5′di(thien-2-yl)thieno[3,2-b]thiophene) (DPP-DTT), [ 21 ] PCP-DTBT, [ 21 ] and PCDTBT [ 21 ] ) have been used to increase the PCE in SP-PHJ PrSCs.Among these materials, polymeric HTMs have been intensively developed for highly effi cient SP-PHJ PrSCs because they can be fabricated by solution processing and exhibit better hole mobility compared to vacuum-processed small-molecule HTMs. [ 3 ] In the fi rst few papers reporting SP-PHJ PrSCs, they were based on the PEDOT:PSS HTM [ 16 ] because PEDOT:PSS is one of the most commonly used HTMs for organic photovoltaics [22][23][24][25][26][27] and organic light-emitting diodes (OLEDs). [ 28,29 ] However, work function (WF) of PEDOT:PSS (≈4.9-5.2 eV) is highly dependent on the ratio of the polymeric acid, PSS relative to PEDOT [ 25,28 ] and therefore may not be suffi ciently high to perfectly match the valence band maxima (VBM) of perovskite materials (e.g., -5.43 eV for methylammonium lead iodide (MAPbI 3 )) for ohmic contact and consequential effi cient charge extraction. [ 9,15,[19][20][21][22][23][24][25][26][27][28][29] Moreover, PEDOT:PSS is dispersed with a large particle size (≈60 nm) in solution; [ 30 ] it precipitates slowly from the solution during storage and is diffi cult to redisperse from the aggregated Organic-inorganic hybrid perovskite solar cells are fabricated using a watersoluble, self-doped conducting polyaniline graft copolymer based on poly(4styrenesulfonate)-g -polyaniline (PSS -g-PANI) as an effi cient hole-extraction layer (HEL) because of its advantages, including low-temperature solution processability, high transmittance, and a low energy barrier with perovskite photoactive layers. Compared with conventional poly(3,4-ethylenedioxythiop hene):poly(styrene sulfonate) (PEDOT:PSS) dispersed in water solution, PSSg-PANI molecules are dissolved in water because of the polymeric dopant covalently bonde...

Researchers achieved ultrahigh efficiency of solution-processed simplified small-molecule OLEDs that use novel universal host materials.

The structural, optical, and room-temperature electrical properties of strained La-doped SrTiO3 epitaxial thin films are investigated. Conductive La-doped SrTiO3 thin films with concentration varying from 5 to 25% are grown by molecular beam epitaxy on four different substrates: LaAlO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, SrTiO3, and DyScO3, which result in lattice mismatch strain ranging from −2.9% to +1.1%. We compare the effect of La concentration and strain on the structural and optical properties, and measure their effect on the electrical resistivity and mobility at room temperature. Room temperature resistivities ranging from ∼10−2 to 10−5 Ω cm are obtained depending on strain and La concentration. The room temperature mobility decreases with increasing strain regardless of the sign of the strain. The observed Drude peak and Burstein-Moss shift from spectroscopic ellipsometry clearly confirm that the La addition creates a high density of free carriers in SrTiO3. First principles calculations were performed to help understand the effect of La-doping on the density of states effective mass as well as the conductivity and DC relaxation time.

PtS2 is a newly developed group 10 2D layered material with high carrier mobility, wide band gap tunability, strongly bound excitons, symmetrical metallic and magnetic edge states, and ambient stability, making it attractive in nanoelectronic, optoelectronic, and spintronic fields. To the aim of application, a large-scale synthesis is necessary. For transition-metal dichalcogenide (TMD) compounds, a thermally assisted conversion method has been widely used to fabricate wafer-scale thin films. However, PtS2 cannot be easily synthesized using the method, as the tetragonal PtS phase is more stable. Here, we use a specified quartz part to locally increase the vapor pressure of sulfur in a chemical vapor deposition furnace and successfully extend this method for the synthesis of PtS2 thin films in a scalable and controllable manner. Moreover, the PtS and PtS2 phases can be interchangeably converted through a proposed strategy. Field-effect transistor characterization and photocurrent measurements suggest that PtS2 is an ambipolar semiconductor with a narrow band gap. Moreover, PtS2 also shows excellent gas-sensing performance with a detection limit of ∼0.4 ppb for NO2. Our work presents a relatively simple way of synthesizing PtS2 thin films and demonstrates their promise for high-performance ultrasensitive gas sensing, broadband optoelectronics, and nanoelectronics in a scalable manner. Furthermore, the proposed strategy is applicable for making other PtX2 compounds and TMDs which are compatible with modern silicon technologies.