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We demonstrate a hybrid light-emitting device (LED) employing a chemical-vapor-deposition grown, centimeter-scale monolayer of WS2 (mWS2) as the active luminescent material embedded within conducti...

Development of multifunctional materials and devices has garnered enormous attention in the field of organic optoelectronics; nevertheless, achieving high mobility together with strong luminescence in a single semiconductor remains a major bottleneck. Here, a new multifunctional semiconductor molecule, 2,7-diphenylbenzo[4,5]thieno[3,2-b]benzofuran (BTBF-DPh), that integrates high charge transporting [1]benzothieno[3,2-b][1]benzothiophene with a strongly emissive furan group, is synthesized and applied in three types of optoelectronic devices, including organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and organic phototransistors (OPTs). OLEDs based on BTBF-DPh as the emissive layer showed a blue emission with CIE coordinates of (0.151, 0.069) and a maximum current efficiency of 2.96 cd A-1 with an external quantum efficiency of 4.23%. Meanwhile, OFETs fabricated with BTBF-DPh thin film manifested a carrier mobility of 0.181 cm2 V-1 s-1, which is comparable to that of thiophene-based counterparts. Additionally, BTBF-DPh-based OPTs exhibited a maximum responsivity and detectivity of 2.07 × 103 A W-1 and of 5.6 × 1015 Jones, respectively. On the one hand, our rationally designed material, BTBF-DPh, has a dense and close-packed structure with an extended π-conjugation, facilitating charge transport through adjacent molecules. On the other hand, the weakened dipole-dipole interactions between BTBF-DPh molecules that resulted from the unambiguous J-aggregation and reduced spin-orbit coupling caused by replacing sulfur atom significantly suppress the exciton quenching, contributing to the improved photoluminescence performance. These results validate that our newly developed BTBF-DPh is a promising multifunctional organic semiconductor for optoelectronic devices.

QD-based high-performance photodetectors (PDs) typically contain hazardous elements such as lead- and cadmium-based materials, raising toxicity and safety concerns for optoelectronic devices. Here,...

Lead-free double perovskite phosphors are promising alternatives to lead halide perovskites for wide uses in optoelectronic applications, but suffer from a low quantum efficiency. Here, we propose ...

Cesium lead halide perovskite nanocrystals have recently become emerging materials for color conversion in visible light communication (VLC) and solid-state lighting (SSL), due to their fast response and desirable optical properties. Herein, perovskite nanocrystal-polymethyl methacrylate (PNC-PMMA) films with red and yellow emission are prepared. The PNC-PMMA films, with optical properties such as a short lifetime and air stability, are used to make broadband color converters based on a high-bandwidth 75 μm blue micro-LED (μLED) for VLC. The yellow-emitting CsPb(Br/I)3 PNC-PMMA has a high bandwidth of 347 MHz, while the red-emitting CsPbI3 PNC-PMMA exhibits a higher modulation bandwidth of 822 MHz, which is ∼65 times larger than that of conventional phosphors. After fixing the two PNC-PMMA films in front of the μLED, a qualified warm white light is generated with a correlated color temperature of 5670 K, a color rendering index of 75.7, and a de L'Eclairage (CIE) coordinate at (0.33, 0.35). Although the color conversion of the blue light sacrifices some received power and slightly reduces the overall bandwidth from 1.130 to 1.005 GHz, a maximum real-time data rate of 1.7 Gbps is still achievable using the non-return-to-zero on-off keying modulation scheme, which is ∼6 times higher than that of the previous record. This study provides a practical approach to develop a considerably high-bandwidth white-light system for both high-speed VLC and high-quality SSL.

All-inorganic CsPbI2Br has attracted intensive attention due to its superior stability against thermal aging and light soaking. However, a large open circuit voltage (VOC) loss results from non-radiative recombination and the mismatched energy level alignment between CsPbI2Br and SnO2/Spiro-MeOTAD charge carrier extraction layer, has been discussed and rarely solved. Perovskite solar cells have theoretically a high value of VOC that can be obtained relative to the wide bandgap. Herein, IC61BA has been employed to modify the SnO2 surface to reduce surface defects, at the same time, a moderate energy level (CsPbI2Br)1-x(CsPbI3)x layer has been introduced at the interface between CsPbI2Br and Spiro-MeOTAD to form graded energy level alignment. As a result, correspondingly, the surface passivation and energy level tailoring reduced the energy level loss from reduced non-radiative recombination and a remarkable open circuit voltage (VOC) improved from 1.13 V to 1.34 V has been achieved, which further boosts the power conversion efficiency (PCE) of 15.56%.

Large-area nanostructured hybrid CH3NH3PbI3 perovskite thin films are fabricated via a direct one-step blade method on nanograting-patterned flexible cyclic olefin copolymer (COC) substrate in ambient condition. The nanostructure of perovskite films can be well controlled with high crystalline quality, revealed by X-ray diffraction (XRD) and photoluminescence (PL) characterization. Flexible photodetectors with nanostructured perovskite thin films demonstrate better performance than their counterparts with flat perovskite films. Numerical modeling of the local energy distribution of incident light reveals the contribution of nanostructures directly textured in perovskite films to the light absorption enhancement. The blade-coated CH3NH3PbI3 photodetector with the nanostructured texturing exhibits a high detectivity of 1.21 × 109 Jones and a responsivity of 0.36 A/W, which are 15% and 47% higher compared with the photodetector with the flat perovskite film, respectively. Our work offers a facile etching-free process that can create high crystalline nanostructured perovskite films for high-performance photodetectors over large-area flexible substrates.

All-inorganic perovskite CsPbBr3–Cs4PbBr6 composite nanocrystals (NCs) were synthesized via a convenient solution process without inert gas protection and systematically studied as green phosphors for light emitting diode (LED) applications. While colloidal composite NCs emit green color with an emission peak at around 515 nm, their thin films on top of blue GaN chips exhibit a redshift of ∼15–20 nm due to subsequential aggregation in solid state. The Commission Internationale De I'eclairage (CIE) chromaticity coordinates of the green LEDs assembled by composite NCs reached (0.201, 0.746) with nearly 100% green ratio. Moreover, the pure green LED displayed a luminous efficiency of 45 lm W−1 under 10 mA driving current. The colloidal CsPbBr3–Cs4PbBr6 composite NCs have the photoluminescence quantum yield (PLQY) as high as 74%. The high PLQY originates from cubic CsPbBr3 NCs well passivated by the zero-dimensional Cs4PbBr6 matrix, substantially suppressing the nonradiative recombination. The comparison between the green LEDs fabricated with pure and composite perovskites imply that the CsPbBr3–Cs4PbBr6 composites with higher quantum yield could be an effective way to get the brightness and the stability of pure green LEDs.

We experimentally demonstrated a high-speed multi-user green and blue laser diode based underwater optical wireless communication (UOWC) system using non-orthogonal multiple access (NOMA) with polarization multiplexing. The system affords eight users with a record sum rate of 18.75 Gbps over 2-m underwater plus 0.5-m free-space channel. The modulation bandwidths of four detachable optical paths with different wavelengths and polarization states all exceed 1.5 GHz. The results suggest that the flexible balance according to both user fairness and overall throughput/sum rate can be achieved via an appropriate power allocation strategy. The joint optimization of driving current and user assignment ensures the feasibility of providing stable high-speed UOWC for multiple users. With the proposed OFDMA-NOMA scheme, user scale expands by twice while the sum rate for single path reaches 3.2 Gbps. Finally, the BER performances of NOMA modality in turbulent underwater environment with air bubbles of different flow rates are also discussed in detail.

Tin-based perovskites with excellent optoelectronic properties are promising candidates for fabricating efficient lead-free perovskite solar cells (PSCs). Unfortunately, Tin-based PSCs exhibited a low efficiency, which mainly arises from serious traps-induced non-radiative recombination, leading into large energy loss with a low voltage. Herein, the polymer poly(ethylene glycol) diacrylate (PEGDA) is employed as a template-agent in FASnI 3 to control nucleation and growth is reported. This FASnI 3 layer showed a compact crystal with large grain size and reduced defects. As a result, the fabricated planar heterojunction device of ITO/PEDOT:PSS/FASnI 3 /PC 61 BM/BCP/Ag showed the power conversion efficiency (PCE) of 6.29% with voltage of 0.45 V.

Organic-inorganic hybrid perovskites have attracted considerable attention due to their superior optoelectronic properties. Traditional one-step solution-processed perovskites often suffer from defects-induced nonradiative recombination, which significantly hinders the improvement of device performance. Herein, treatment with green antisolvents for achieving high-quality perovskite films is reported. Compared to defects-filled ones, perovskite films by antisolvent treatment using methylamine bromide (MABr) in ethanol (MABr-Eth) not only enhances the resultant perovskite crystallinity with large grain size, but also passivates the surface defects. In this case, the engineering of MABr-Eth-treated perovskites suppressing defects-induced nonradiative recombination in perovskite solar cells (PSCs) is demonstrated. As a result, the fabricated inverted planar heterojunction device of ITO/PTAA/Cs0.15 FA0.85 PbI3 /PC61 BM/Phen-NADPO/Ag exhibits the best power conversion efficiency of 21.53%. Furthermore, the corresponding PSCs possess a better storage and light-soaking stability.

To address the double pressure of scarce resources and regional industrial isomorphism, this paper applied the concepts of exergy and embodied resources based on economic input–output (I–O) data. We constructed the embodied resources networks among the regional industries of Beijing-Tianjin-Hebei (also known as Jing-Jin-Ji) in China. We analyzed the rules of embodied resources consumption in the area’s industries, identified the core community structures, and studied the characteristics of industrial homogeneity through regional comparisons. The results showed that the dependence on scarce resources of industrial operations in Beijing was less than in Jin-Ji, while the dependence on finance, technology, information, and other service resources in Beijing was higher than in Jin-Ji. The I–O efficiency of embodied resources among industries and the agglomeration of correlation relationships in industries with large embodied resources were higher than in Jin-Ji. The industrial coincidence degree in the ”bridge” industries and in the core community in Jin-Ji was higher than in Jing-Jin and Jing-Ji, which means the industrial homogeneous competition of Jin-Ji was higher, too. This study makes a significant contribution toward promoting the dislocation development of regional industries, accelerating the coordination of resources, and reducing homogeneity competition.

The cubic phase CsPbI 3 with a suitable direct band gap of 1.73 eV has been widely explored as the light absorption layer for pure inorganic perovskite solar cells. However, the phase transition of CsPbI 3 will seriously affect its application prospect. As an effective method, the phase transition of CsPbI 3 in cubic phase can be significantly suppressed by using hydroiodic (HI) acid as a precursor additive. Here, we have systematically studied the mechanism of promoting the film formation of cubic phase CsPbI 3 and the effect on its photovoltaic performance by regulating the addition of HI acid. The results show that the addition of HI acid has an obvious effect on the film morphology, grain size, crystal structure, light absorption and band structure of CsPbI 3 . The optimized perovskite solar cells with ITO/PEDOT:PSS/CsPbI 3 /PCBM/Ag as the device structure achieved the highest efficiency of 4.8%.

Vertical cavity surface emitting laser (VCSEL) array is increasingly integrated in consumer electronic devices as light sources for biometrics and interaction between terminals. In this study, we proposed a high-speed multi-user optical wireless communication (OWC) method based on a near-infrared VCSEL array, and then experimentally demonstrated a two-user quadrature amplitude modulation (QAM) orthogonal frequency division multiple access (OFDMA) system in a typical indoor environment over a 2-m link. The measured 3-dB bandwidth is around 1.02 GHz for both links, then the maximum sum rate reaches up to 2.7 Gbps for two users with bit-error-rate (BER) of 0 and 3.2 × 10−3 respectively. The designed VCSEL-based QAM–OFDMA OWC system depicts the feasibility of potential scenarios for the interactive information transfer between terminals.

Photodetectors (PD) with high detectivity, high quantum efficiency and fast response are fundamental units to achieve sensors, imagers, and many others functional optoelectronics. Here we demonstrate high performance vertical stacked 2D MoS2/CuPc heterojunction based photodetectors with high sensitivity, high external quantum efficiency and ultrafast response time. The functional p-type organic thin film of CuPc was thermally evaporated on n-type two-dimension (2D) MoS2 monolayer to create an ideal type II heterojunction interface, where ultrafast charge transfer (CT) occur in 16 ps, followed by effective exciton separation and charge collection. As a result, photoresponse time as fast as 436 μs has been obtained for 2D MoS2/CuPc PDs, as well as a profound responsivity of 3.0 × 10 3 A/W and a detectivity of 2.0 × 1010 Jones with a peak external quantum efficiency (EQE) of 483%. This work suggests a feasible route to develop ultrasensitive visible light photodetector by 2D materials.

It is demonstrated that squaraine:PC70BM blends can result in solar cells with high efficiency and fill factor when the nano­structure scale is increased to lead to conduction of photogenerated carriers to the electrodes. Morphological control occurs by a combination of thermal and solvent annealing of these small molecule, solution-processed bulk heterojunction cells. Peak efficiencies of a population of devices is 5.2% at fill factors of 0.5 are achieved under optimized conditions.

We study a family of functionalized squaraine (fSQ) donors for absorbing in the near-infrared (NIR) and green spectral regions. The NIR-absorbing materials are the symmetric molecules 2,4-bis[4-(N-phenyl-1-naphthylamino)-2,6-dihydroxyphenyl]squaraine (1-NPSQ), 2,4-bis[4-(N,N-diphenylamino)-2,6 dihydroxyphenyl]squaraine, and 2,4-bis[4-(N,N-dipropylamino)-2,6-dihydroxyphenyl]squaraine. The green light absorbing donors are asymmetric squaraines, namely, 2,4-bis[4-(N,N-diphenylamino)-2,6-dihydroxyphenyl]squaraine and 2-[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]-4-diphenylamino]squaraine. Substitution of the arylamine groups enhances intermolecular packing, thereby increasing hole transport and the possibility of forming extended nanocrystalline junctions when annealed. Nanocrystalline solar cells based on fSQ and a C(60) acceptor have V(oc) = 1.0 V and fill factors 0.73 ± 0.01. Solar cells incorporating annealed 1-NPSQ films result in a power conversion efficiency of 5.7 ± 0.6% at 1 sun, AM1.5G illumination.

Two squaraine (SQ) donor molecules with different absorption bands are blended together for better coverage of the solar spectrum. The blend SQ device shows a significant improvement compared with single SQ donor devices. By applying a solvent annealing process and a compound buffer layer, a power-conversion efficiency of 5.9 ± 0.3% is achieved under 1 sun illumination.

It has been a challenge to achieve high efficiency organic photovoltaics (OPV) that absorb long wavelength solar radiation without incurring unacceptable reductions in open circuit voltage (V oc ) or charge separation efficiency. Based on the parent structure of the 2, 4-bis[4-(N, N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (SQ), we have increased V oc using a family of highly near-infrared absorbing SQs, achieving values as high as 0.94 V. These SQ donors are: 2, 4-bis[4-(N-Phenyl-1-naphthylamino)-2,6-dihydroxyphenyl] squaraine (1-NPSQ),2,4-bis[4-(N, N-diphenylamino)-2,6 dihydroxyphenyl] squaraine (DPSQ), 2,4-bis[4-(N, N-diphenylamino)-2,6-dihydroxyphenyl] asymmetric squaraine (DPASQ). The spin-cast SQ, 1-NPSQ, DPSQ and DPASQ donors are then coated with the acceptor C 60 to form bulk heterojunction (BHJ) solar cells that take advantage of their exceptionally high absorption coefficient and nanocrystalline morphology to overcome the short diffusion length characteristic of these materials. Combined with a high short-circuit current density (J sc =10.6 mA/cm2) and high fill factor (FF=0.64), the optimized 1-NPSQ/C 60 photovoltaic cells with 1-NPSQ annealed at elevated temperature have a power conversion efficiency of η p as high as 6.0% (correcting for solar mismatch) at 1 sun (AM 1.5G) simulated solar illumination, which to our knowledge is the highest efficiency reported to date for small molecule OPVs.

It is common to incorporate a cathode-side buffer layer in organic photovoltaic devices (OPVs) to mitigate damage from the evaporation of metal onto the underlying acceptor layer (e.g. C 60 ), which can lead to exciton quenching and/or a barrier to charge extraction. Additionally, these materials can act as both an optical spacer and an exciton blocking layer. One class of buffer layers consists of a wide bandgap material (e.g. bathocuproine), that transports carriers via damage-induced midgap states. A second class of buffers consists of a material such as tris(acetylacetonato) ruthenium(III) (Ru(acac) 3 ), which has a small highest occupied molecular orbital (HOMO) energy. In that case, electrons from the C 60 and holes from the cathode recombine at the C 60 /Ru(acac) 3 interface. In this work, we introduce a third class of buffer that, due to alignment of its lowest unoccupied molecular orbital with that of the acceptor, allows for low resistance transport of electrons between the acceptor and cathode. By utilizing 3,4,9,10 perylenetetracarboxylic bisbenzimidazole (PTCBI) as a buffer layer, we show improved fill factor in squaraine/C 60 -based devices without a loss in open-circuit voltage or photocurrent, leading to a >20% increase in power conversion efficiency. Although limited exciton transfer occurs from C 60 to PTCBI, the short exciton diffusion length of PTCBI, coupled with the lack of loss at the C 60 /PTCBI interface, suggests that PTCBI also blocks excitons from quenching at metal-induced defects that are present in the absence of a buffer layer.

Spin-cast 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]squaraine (SQ) thin films only 62 A thick are converted from amorphous to polycrystalline via postannealing at elevated temperatures. The surface roughness of the SQ films increases by a factor of 2, while selected area electron diffraction spectra indicate an increase in the extent of postannealed film crystallinity. Dichloromethane solvent annealing is also demonstrated to increase the exciton diffusion length of SQ by a factor of 3 over thermally annealed SQ films as a result of further enhancement in crystalline order. We find that the roughened surface features have a length scale on the order of the exciton diffusion length. Hence, coating the donor SQ with the acceptor, C(60), results in a nearly optimum controlled bulk heterojunction solar cell structure. Optimized SQ/C(60) photovoltaic cells have a power conversion efficiency of eta(p) = 4.6 +/- 0.1% (correcting for solar mismatch) at 1 sun (AM1.5G) simulated solar intensity, and a corresponding peak external quantum efficiency of EQE = 43 +/- 1% even for the very thin SQ layers employed.

Power efficiencies >60% have been predicted for idealized quantum dot (QD) intermediate band solar cells. This goal has not yet been realized, due in part to nonidealities that result in charge trapping followed by recombination of photocarriers in the QDs, and the lack of an optimal materials combination. To eliminate charge trapping, a p+−i−n+ cell employing QDs buried within a high band gap barrier layer is proposed and analyzed. The maximum solar power conversion efficiency under AM1.5 spectral radiation of an example GaAs-based photovoltaic cell employing 10−20 layers of InAs QDs surrounded by AlxGa1-xAs barriers in the junction built-in depletion region can be as high as 45%. Higher efficiencies are anticipated for InP-based cells. This represents a significant improvement over GaAs homojunction cells with maximum efficiencies of

The present disclosure relates to photosensitive optoelectronic devices comprising a compound blocking layer located between an acceptor material and a cathode, the compound blocking layer comprising: at least one electron conducting material, and at least one wide- gap electron conducting exciton blocking layer. For example, 3,4,9, 10 perylenetetracarboxylic bisbenzimidazole (PTCBI) and 1,4,5, 8-napthalene-tetracarboxylic- dianhydride (NTCDA) function as electron conducting and exciton blocking layers when interposed between the acceptor layer and cathode. Both materials serve as efficient electron conductors, leading to a fill factor as high as 0.70. By using an NTCDA/PTCBI compound blocking layer structure increased power conversion efficiency is achieved, compared to an analogous device using a conventional blocking layers shown to conduct electrons via damage-induced midgap states.

2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (SQ) is used as a donor material in vapor deposited organic heterojunction photovoltaic cells. Devices with the structure indium tin oxide/SQ (x)∕C60 (400A)/bathocuproine (100A)∕Al (1000A), where x=65, 110, 150, and 200A were compared. Devices with x=65A exhibited a power conversion efficiency of 3.1% under 1sun, AM1.5G simulated solar irradiation, giving an open circuit voltage of 0.76±0.01V, a short circuit current of 7.01±0.05mA∕cm2, and a fill factor of 0.56±0.05. Thicker SQ films lead to lower short circuit currents and fill factors, giving conversion efficiencies in the range of 2.6% to 3.2%. The demonstration of sublimable SQ as a donor material opens up a family of compounds for use in small molecule based heterojunction photovoltaics.

We demonstrate high open circuit voltage photovoltaic cells achieved by reducing the electron leakage current through the introduction of both organic and inorganic electron blocking layers between the donor layer and the anode contact. As an example, the blocking layers reduce the dark current in tin (II) phthalocyanine (SnPc)∕C60 solar cells with response across the visible and near infrared spectral region up to a wavelength of 1000nm, is decreased by two orders of magnitude compared to cells lacking the layers, resulting in a doubling of the open circuit voltage. The structure: indium tin oxide/electron blocker/SnPc (100A)∕C60 (400A)/bathocuproine (100A)∕Al, has a power conversion efficiency of (2.1±0.1)% at 1sun, standard AM1.5G solar illumination. This work demonstrates the importance of reducing dark current to achieve high organic thin film photovoltaic cell efficiencies.

We demonstrate top-illuminated, inverted, small molecule photovoltaic cells grown on reflective substrates employing copper phthalocyanine as the donor and 3,4,9,10-perylenetetracarboxylic bis-benzimidazole as the acceptor, with a sputter-deposited transparent indium tin oxide top cathode and a metal anode, thereby reversing the conventional charge extraction properties of these contacts. The best device achieved a peak power conversion efficiency of 0.74±0.03%, reasonably consistent with the optical simulations under 1sun AM1.5G illumination giving 0.83±0.02%. This work suggests that inverted organic solar cells grown on reflective substrates have potential uses such as for power-generating coatings on opaque surfaces.

We package a low-powered 850 nm VCSEL and design a high-speed facile optical wireless communication system using power-bit-loading algorithm over 1 m free space link. The maximum data rate is up to 8.23Gbps. © 2020 The Author(s)