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A mesoporous SnO2-electron transport bilayer with a high surface-area-to-volume ratio is developed for application in inkjet-printed PSCs (IJP-PSCs). The use of SnO2-bilayer has uplifted the efficiency of IJP-PSCs up to a maximum of 16.9%.

Surface modification and wetting state transformation of ZnO based nanomaterials have been extensively investigated due to their substantial roles in current industrial applications. In this work, we demonstrated the formation of highly crystalline and ordered Bi/ZnO nanorods arrays (Bi/ZNRs) grown on FTO substrate via a feasible hydrothermal method, as a function of reaction time (t). The lateral diameter of the nanostructures were found increased from 23 nm to 43 nm when the reaction time increased from 30 min to 90 min. An in-depth analysis and incisive mechanism of crystal growth under the function of reaction time were proposed. The crystal defect which originated from different Bi incorporation pathways has been declared as the main factor altering the optical energy, electrical properties and band structure of Bi/ZNRs. The Bi/ZNRs showed a higher localize current of 14.5 pA as compared to pristine ZNRs under an 6V applied bias condition, revealing the nature of Bi as a pentavalent dopant that contributed to a density of free electron. Additionally, the Bi/ZNRs also revealed a red shifted in optical energy band gap and exhibit a wetting transition from hydrophobic to hydrophilic textured surface. The novel nanostructures reported herein exhibit interesting physical and optical properties for the fabrication of high performance optoelectronic devices.

State-of-the-art perovskite solar cells (PSCs) have exhibited a record-breaking power conversion efficiency (PCE) of 25.2% with remarkable operational stability, surpassing the PCE of silicon-based...

Organic light-emitting diodes (OLEDs) are widely commercialized in the display market due to many advantages such as wide color gamut, outstanding flexibility, and high contrast ratio. However, the...

Fabrication of high-quality, low-cost and large-scale solution processable inorganic hole-transport layers (HTLs) for planar p–i–n perovskite solar cells (PSCs) is still a challenge that must be overcome to produce stable devices. Herein, we demonstrate the development of large-scale (>60 cm2), highly uniform and dopant-free NiO films via spray pyrolysis, and we show their subsequent application as a HTL in triple-cation PSCs. The spray deposited NiO films are highly crystalline in nature with a (111) oriented nanostructured morphology. We show outstanding optoelectronic properties (Eg ≈ 3.78 eV, work function ≈ 4.86 eV) that led to improved optical absorption and better energy band alignment with the perovskite layer. Compared to the state-of-the-art PEDOT:PSS based PSCs, these spray-deposited NiO-based devices exhibited an excellent power conversion efficiency (PCE) of ∼17.3%, which is the highest reported value for dopant-free NiO-based PSCs prepared via the spray-deposition technique. More importantly, the NiO based PSCs also showed extremely high reproducibility and scalable device performance, achieving a PCE of 12.3% at an aperture area of ∼1.04 cm2. Moreover, unencapsulated PSCs employing spray-deposited NiO exhibited outstanding stability, maintaining ∼87% PCE after 4500 h of aging in a N2 atmosphere, and encapsulated devices exhibited much better stability retaining >82% of the initial PCE after 200 h in a harsh environment (85 °C, 85% relative humidity).

The performance and scalability of perovskite solar cells (PSCs) is highly dependent on the morphology and charge selectivity of the electron transport layer (ETL). This work demonstrates a high-speed (1800 mm min

A simple, cost-effective, and one-step procedure for fabrication of gold-nanoparticle-transition metal oxide (Au-TMO) thin films with tuned optical and structural properties is described. In this approach, a homogeneous mixed precursor solution was used to fabricate Au-MoO3 and Au-WO3 thin films via a spray pyrolysis technique. The in-situ grown Au nanoparticles in the host matrices exhibited a characteristic surface plasmon resonance absorption in the visible-NIR region with peak positions at λmax ≈ 600 nm, ≈550 nm, and ≈575 nm for Au-MoO3, Au-a-WO3 (amorphous), and Au-h-WO3 (hexagonal) films, respectively. The structural and morphological characterization measurements confirmed that the high purity in-situ grown Au nanoparticles were 10–100 nm in size, and individual particles were embedded into the host matrices. These films were applied as plasmon-induced photoelectric conversion devices with ITO/NiOx/Au-WO3/Ag structures as a prototype device. The device exhibited a short-circuit current of 0.1 mA with an open-circuit voltage of ∼1.4 V under one-sun illumination. Our one-step fabrication approach is highly promising for fabricating other Au-TMOs thin films with tuned optical properties on a large area and can be applied for various optoelectronic applications.

Transparent conducting electrodes (TCEs) have played a pivotal role in driving the continuous development of optoelectronics technologies, which include organic optoelectronic applications. In recent years, there has been huge interest in designing innovative TCEs to replace the conventional indium tin oxide (ITO) electrodes, which suffer from complex fabrication issues and are incompatible with flexible, wearable electronic devices. In this regard, TCEs based on metal meshes are considered to be the best candidates because of their inherently high electrical conductivity, optical transparency, mechanical robustness and, more importantly, cost-competitiveness. In this review, we describe the technology developments of metal mesh-based transparent conductors and their applications in organic optoelectronic devices, including organic and perovskite solar cells, organic light emitting diodes, supercapacitors, electrochromic devices etc. Specifically, we discuss the fundamental features, optoelectronic properties, fabrication techniques and device applications of metal mesh TCEs. We also highlight the important criteria for evaluating the performance of metal mesh electrodes and propose some new research directions in this emerging field.

Crystallinity and band offset alignment of inorganic electron acceptor play a vital role in enhancing the device performance of inverted organic solar cell (IOSC). In this report, homogenous and vertically-aligned chemical treated ZnO nanorods (ZNR) were successfully grown on fluorine-doped tin oxide (FTO) substrate via a fully-solution method. It was found that the morphology of ZnO was fine-tuned from truncated surface to tubular structure under both of the anionic (KOH) and protonic (HCl) treatment. An extraordinary defect quenching phenomenon and hyperchromic energy band edge shift were observed in 0.1 M KOH-treated ZNR proven by the highest (0 0 2) peak detection and the lowest defect density. Compared with the pristine sample, the 0.1 M KOH-treated ZNR device showed a remarkable improvement in power conversion efficiency (PCE) up to 0.32%, signifying the effectiveness of anodic treatment. The robust correlation between the dependency of chemical treated ZNR and the device performance was established. This work elucidates a feasible method towards efficient IOSC devices development.

Charge transport dynamics in ZnO based inverted organic solar cell (IOSC) has been characterized with transient photocurrent spectroscopy and localised photocurrent mapping-atomic force microscopy. The value of maximum exciton generation rate was found to vary from 2.6 × 1027 m−3s−1 (Jsat = 79.7 A m−2) to 2.9 × 1027 m−3s−1 (Jsat = 90.8 A m−2) for devices with power conversion efficiency ranging from 2.03 to 2.51%. These results suggest that nanorods served as an excellent electron transporting layer that provides efficient charge transport and enhances IOSC device performance. The photovoltaic performance of OSCs with various growth times of ZnO nanorods have been analysed for a comparison between AM1.5G spectrum and local solar spectrum. The simulated PCE of all devices operating under local spectrum exhibited extensive improvement with the gain of 13.3–13.7% in which the ZnO nanorods grown at 15 min possess the highest PCE under local solar with the value of 2.82%.

In recent years, extensive research has been undertaken to develop fiber-shaped optoelectronic devices, because they are aesthetically pleasing, light in weight, and exhibit superior light emitting properties when compared with conventional planar analogues. In this work, we have successfully developed hollow-fiber shaped organic light emitting diodes (HF-OLED) with an exceptionally high luminance and facile color tunability. The HF-OLED device was fabricated by hierarchically depositing amorphous indium-doped tin oxide electrode on a hollow-fiber, followed by the sequential deposition of light-emitting organic layers and Al cathode. The external quantum efficiency of the HF-OLED is more than ∼2.0 times higher than that of a planar-OLED. The experimental results are in good agreement with the output of optical simulations, revealing that the use of a hollow-fiber has contributed to a ∼2.3 times improvement in light extraction efficiency. Furthermore, the color emission of a single HF-OLED device could be easily tuned from a green to yellowish-green wavelength after the injection of a super-yellow solution. The novel color tunable nature of the HF-OLED further broadens its application in the field of modern lighting and display technology.

In this study, we designed a highly flexible, mechanically robust Ag mesh/ITO composite transparent conducting electrode (TCE) integrated with a microlens array (MLA) to improve the light extraction of organic light-emitting diodes (OLEDs). The mechanical flexibility and durability of a flexible OLED based on a Ag mesh/ITO composite TCE were superior to those of a device with a conventional ITO electrode, retaining ∼100% initial luminance for up to 1000 cycles at a bending radius of ∼2 mm. Additionally, both experimental and theoretical characterizations suggest that the performance of a flexible OLED, such as its external quantum efficiency and angular-dependent emission, vastly improves after the incorporation of MLA due to the additional light scattering induced by the MLA. The combined use of Ag mesh and MLA is a practical way to overcome the brittleness of ITO and improve the out-coupling efficiency of flexible OLEDs (enhancement ratio of ∼1.51).

All inorganic CsPbBr3 perovskite quantum dots (PeQDs) have emerged as great candidates for next-generation perovskite quantum dots light-emitting diodes (PeQLEDs) applications due to their excellent optoelectronic and light-emitting properties. However, the performance of CsPbBr3 based PeQLEDs is hindered by (i) the long-chain, synthetic insulating ligands on PeQDs surfaces and (ii) the inherently high refractive index (n) of the PeQDs that often leads to internal light confinement loss. These major shortcomings are addressed by introducing a short-chain ammonium moiety, namely phenethylammonium bromide (PEABr), via spin-coating to passivate the surface of the PeQDs films. PEABr passivation can effectively annihilate the intrinsic bromide vacancies of PeQDs and simultaneously tune the refractive index of the PeQDs films. The reduced n-mismatch between the emitter and the charge transporting layers suppresses the waveguide loss after PEABr passivation and significantly elevates the external quantum efficiency (EQE) and maximum luminance of the PeQLEDs from ~ 1.0% to ~ 6.85% and ~ 1300 cd m−2 to ~ 13000 cd m−2, respectively. More importantly, the environmental stability of the PeQDs also improves remarkably following PEABr passivation. The alky cation engineering demonstrated herein is a facile yet efficient approach to simultaneously boost the performance and stability of CsPbBr3 PeQDs.

Incorporating cadmium sulfide quantum dots (CdS QDs) onto ZnO nanorod (ZNRs) has been investigated to be an efficient approach to enhance the photovoltaic performance of the inverted organic solar cell (IOSC) devices based on ZNRs/poly (3-hexylthiophene) (P3HT). To synthesize CdS/ZNRs, different durations of deposition per cycle from 1 to 9 min were used to deposit CdS via SILAR technique onto ZNRs surface grown via hydrothermal method at low temperature on FTO substrate. In typical procedures, P3HT as donor polymer were spun-coating onto CdS/ZNRs to fabricate IOSC devices, followed by Ag deposition as anode by magnetron sputtering technique. Incorporation of CdS QDs has modified the morphological, structural, and optical properties of ZNRs. Incorporation of CdS QDs onto ZNRs also led to higher open circuit voltage (Voc) and short circuit current density (Jsc) of optimum ZNRs/CdS QDs devices due to the increased interfacial area between ZNRs and P3HT for more efficient exciton dissociation, reduced interfacial charge carrier recombination as a result of lower number of oxygen defects which act as electron traps in ZnO and prolonged carrier recombination lifetime. Therefore, the ZNRs/CdS QDs/P3HT device exhibited threefold higher PCE (0.55%) at 5 min in comparison to pristine ZNR constructed device (0.16%). Overall, our study highlights the potential of ZNRs/CdS QDs to be excellent electron acceptors for high efficiency hybrid optoelectronic devices.

Summary Roll-to-roll (R2R) fabrication of flexible and transparent all-solid-state supercapacitors (FT-ASSCs) is extremely challenging because of the classic trade-off between transparency and capacitance. In this work, we develop fully three-dimensional (3D)-printed, sandwich-type FT-ASSCs comprised of 3D line-patterned carbon black (CB)/Ag/CB electrodes on a transparent dialysis membrane (DM) separator. By tailoring the line pitch of the 3D electrodes, our FT-ASSC is able to achieve more than 80% optical transmittance and significantly higher areal capacitance than an opaque ASSC. More importantly, the performance of 3D-printed FT-ASSCs is unrestricted by the transparency-capacitance trade-off, and they exhibit a superior capacitive figure of merit value compared with state-of-the-art FT-ASSCs reported in the literature. Additionally, our FT-ASSCs demonstrate excellent cyclic stability and mechanical robustness because of the chemical and mechanical stability of the DM separator and effective encapsulation of polyurethane. The single-flow 3D printing technique introduced here can meet the requirements for industrial-scale R2R manufacturing of energy storage devices.

Hybrid lead-halide perovskites are widely used in a variety of optoelectronic applications, including perovskite solar cells (PSCs), perovskite light-emitting diodes (PeLEDs), perovskite photodetectors (PPDs), and scintillators. Recently, it was demonstrated that bulky organic cations (BOCs) can be used as surface passivation agents to fine-tune the dimensionality of lead-halide perovskites, making it possible to tailor their optoelectronic properties and enhance their stability. This special feature has further improved the commercialization potential of perovskite-based optoelectronic devices. In this article, we provide a comprehensive review of the recent progress in low/multidimensional perovskites prepared via BOC treatment and their performance in various optoelectronic devices. We begin by introducing the special features and fundamental properties of lead-halide perovskites with different dimensionalities and the working mechanism of BOC treatments. Thereafter, we separately highlight and discuss the device architecture and performance breakthroughs of BOC-treated perovskites in (i) PSCs, (ii) PeLEDs, and (iii) PPDs and scintillators, emphasizing works published from 2018 till now. For each application, the influence of BOC treatments on device performance and stability is discussed. At the end of this review, we provide our insights on future challenges and commercialization opportunities for BOC-treated perovskites in the field of optoelectronics.

Flexible organic light-emitting diodes (OLEDs) are used widely in optoelectronic devices, with possible new applications, including foldable/rollable displays. Unique features of flexible OLEDs included high brightness, low power consumption, and flexibility. The performance of a flexible OLED is frequently hindered by refractive index difference between the air and the flexible substrate medium, leading to inefficient light outcoupling. To address this issue, we developed a mechanically robust oxide/metal/oxide (OMO) structured transparent conducting electrode (TCE), integrated with silica nanoparticles–based antireflective (AR) film, to improve the light extraction efficiency of flexible OLEDs. The AR-OMO structures were prepared on polyethylene terephthalate substrates using a combination of plasma-enhanced chemical vapor deposition and magnetron sputtering . Our results show that an OLED device based on AR-OMO TCE exhibits higher luminance efficiency ( LE) and total external quantum efficiency (EQEtot ) than devices based on pristine OMO or an indium tin oxide structure due to the presence of AR film that suppresses waveguided-mode light loss at the air-substrate interface. The champion AR-OMO-based flexible OLED devices achieved an LE of 12.3 cd/A and an EQEtot of 5.0%. The AR-OMO device also demonstrated outstanding mechanical flexibility, retaining 100% of its initial luminance up to a bending radius of 6 mm.

Metal oxide based optical absorbance gas sensor (MOAGS) exhibits underlying potential to be the most promising energy-saving device with long-term stability and excellent sensing performance. In this work, a self-customized automated MOAGS setup was employed to study the carbon monoxide (CO) gas sensing performance between the hydrothermal synthesized ZnO nanorod (ZNR) and Indium-doped ZnO nanorod (IZNR) operating at room temperature of (25 ± 1)°C. Specifically, it was found that the In 3+ was evenly doped into ZnO lattice which in turn increased the defect density and generated an impurity state within the energy band structure of ZnO. The results showed that 0.04 mol% IZNR exhibited an optimum sensing performance with absolute optical absorbance change (OAC) of 0.067 a.u. under the 10 ppm of CO gas testing environment with fastest respond and recovery time. The dependency of sensing performances to the optical band gap energy alteration and the defect state was evaluated. This work provides a simple and feasible route to develop the room temperate operating MOAGS for hazardous gas detection.

Surface modification in nanostructures enables a thorough control on intrinsic properties, surface activity and enhancement of their usefulness in several device applications. The crystal growth and design in a low temperature regime (

The controllable growth of metal sulfide–metal oxide based nanomaterials with a tunable band gap structure is vital in the fabrication of new generation optoelectronic devices. In this paper, two-dimensional hierarchical CdS/ZnO nanorod arrays were successfully grown via a low temperature hydrothermal-SILAR method. A concise mechanism related to the surface and band gap modification on the CdS/ZnO nanorods was investigated under various CdS deposition cycles (N). The diameter and surface roughness properties of the sample were found to be linearly dependent on the value of N. A bathochromic shift in the optical energy band gap revealed the quantum size effects of the CdS/ZnO nanorods, as well as the induced interface band state and energy band split in the ZnO band state. An impressive improvement in the crystallinity of the sample was also observed under the CdS treatment. The correlation between the optical band gap and photovoltaic efficiency was evaluated. The results proved that the ZnO nanorod/CdS devices exhibited a threefold higher power conversion efficiency in comparison to a pristine ZnO nanorod device.

A simple low-temperature solution processed bismuth-doped ZnO nanorods (NRs) and poly(3-hexylthiophene) (P3HT) were used as electron acceptor and donor, respectively, in a hybrid inorganic–organic photovoltaic system. Controlling Bi precursor concentration via solution processing (hydrothermal method) plays an important role in altering the morphology, structure, and intrinsic defects of ZnO NRs. Interstitial doping of Bi–Bi2O3 into ZnO (BiZO) NRs results in simultaneous improvement of the open circuit voltage and short circuit current density primarily due to prolonged charge carrier recombination lifetime, increased donor–acceptor interfacial areas with efficient exciton dissociation, and charge carrier mobility. As a result, the power conversion efficiency of the 2 wt % BiZO NRs-P3HT device was significantly enhanced by 55% compared with that of the pristine device. Overall, our study highlighted the immense potential of BiZO NRs as an excellent electron acceptor for fabrication of hybrid optoelectroni...

ZnO nanofilm has been irreplaceable especially in nanoscale researches due to the unique tunability of its morphology and semiconductor properties, suiting the needs of different applications. In present work, we employed direct current (DC) magnetron sputtering technique to deposit ZnO films, aiming to elucidate the relationship between sputtering pressure and the morphology, crystallinity and defect states of the films. The sputtering pressure was deliberately varied at low pressure regime and highly crystalline (002) plane bounded ZnO nanofilms were successfully prepared at the pressure condition of 15.0 mTorr. With increasing sputtering pressure, photoluminescence analysis indicates that more intrinsic defects were created in ZnO lattice structure. In contrast, Hall Effect measurement shows that the sheet resistivity of ZnO film reduced, corresponding to the increasing number of free charge carriers inside the films. The thermodynamic and kinetic transitions among the reactants and the texture of sputtering surface are the major factors affecting the formation of high quality ZnO nanofilms. The highly crystalline nanograined ZnO films reported in this study is a very promising structure with interesting material properties for future optoelectronic and spintronic applications.

The effect of growth durations on the formation of ZnO nanorods thin film under continuous microwave irradiation was investigated. ZnO nanorods were synthesized using a microwave-assisted seed mediated growth method. ZnO nanoseed layer was prepared on Si substrate using a sol-gel technique. The microwave-assisted seed mediated growth of ZnO nanorods was conducted at different growth durations, namely 15, 20 and 30 min by fixing the irradiation power at 110 W. XRD diffractogram shows that the hexagonal wurtzite crystal structure for all the samples exhibited a preferred growth orientation along the c-axis. FESEM micrographs reveal with increasing heating duration, the average diameter of ZnO nanorods increased considerably and contrarily, the surface density of nanorods reduced. PL analysis suggests that an extended growth duration has resulted in the creation of defects in nanorods films owing to the insufficient supply of precursor ions during growth process.

One-dimensional ZnO nanorods (ZNRs) synthesized on fluorine-doped tin oxide (FTO) glass by hydrothermal method were modified with cadmium sulfide quantum dots (CdS QDs) as an electron transport layer (ETL) in order to enhance the photovoltaic performance of inverted organic solar cell (IOSC). In present study, CdS QDs were deposited on ZNRs using a Successive Ionic Layer Adsorption and Reaction method (SILAR) method. In typical procedures, IOSCs were fabricated by spin-coating the P3HT:PC61BM photoactive layer onto the as-prepared ZNRs/CdS QDs. The results of current-voltage (I-V) measurement under illumination shows that the FTO/ZNRs/CdS QDs/ P3HT:PC61BM/ PEDOT: PSS/Ag IOSC achieved a higher power conversion efficiency (4.06 %) in comparison to FTO/ZNRs/P3HT:PC61BM/PEDOT: PSS/Ag (3.6 %). Our findings suggest that the improved open circuit voltage (Voc) and short circuit current density (Jsc) of ZNRs/CdS QDs devices could be attributed to enhanced electron selectivity and reduced interfacial charge carrier recombination between ZNRs and P3HT:PC61BM after the deposition of CdS QDs. The CdS QDs sensitized ZNRs reported herein exhibit great potential for advanced optoelectronic application.

Anion passivation effect on metal-oxide nano-architecture offers a highly controllable platform for improving charge selectivity and extraction, with direct relevance to their implementation in hybrid solar cells. In current work, we demonstrated the incorporation of fluorine (F) as an anion dopant to address the defect-rich nature of ZnO nanorods (ZNR) and improve the feasibility of its role as electron acceptor. The detailed morphology evolution and defect engineering on ZNR were studied as a function of F-doping concentration (x). Specifically, the rod-shaped arrays of ZnO were transformed into taper-shaped arrays at high x. A hypsochromic shift was observed in optical energy band gap due to the Burstein-Moss effect. A substantial suppression on intrinsic defects in ZnO lattice directly epitomized the novel role of fluorine as an oxygen defect quencher. The results show that 10-FZNR/P3HT device exhibited two-fold higher power conversion efficiency than the pristine ZNR/P3HT device, primarily due to the reduced Schottky defects and charge transfer barrier. Essentially, the reported findings yielded insights on the functions of fluorine on (i) surface –OH passivation, (ii) oxygen vacancies (Vo) occupation and (iii) lattice oxygen substitution, thereby enhancing the photo-physical processes, carrier mobility and concentration of FZNR based device.

For nanoscale fabrication of organic photovoltaic device, the utilization of a hole extraction layer (HEL) is essential to prevent the wrong flow of charge carriers and overcome the Schottky barrier at electrode-polymer interface. In recent years, the degradation issue of PEDOT:PSS based device which arises from its acidic nature and extremely hygroscopic properties has prompted researchers to find an appropriate transition metal oxide as replacement. In current work, we introduced an entirely solution-processed substoichiometric vanadium oxide (V2Ox) as HEL in inverted polymer:fullerene based device. We demonstrated the efficiency of substoichiometric V2Ox layer in enhancing the device performance of inverted organic solar cells, with the PCE of the device increased from 1.91 to 2.89%. The V2Ox prepared herein was found to exhibit broad optical absorption, highly selective charge transporting properties and excellent film transparency. A robust correlation between the hole extraction nature and electroni...

Band gap energy and surface defect on the nanostructure play an important role especially in determining the performance and properties of the optical based gas sensor. In this report, ZnO nanorods (ZNRs) with various growth concentrations were successfully synthesized using a facile wet chemical approach. The gas sensing performance of the ZNRs samples with different concentrations were tested toward the highly hazardous carbon monoxide (CO) gas at a concentration of 10 ppm operated at room temperature. It was found that the 40 mM ZNRs sample exhibited the highest response coupled with the shortest response time (123.3 ± 1.3 s) and recovery time (7.7 ± 0.3 s). The high response and accelerated sensing reaction were attributed to the band gap narrowing of the 40 mM ZNRs induced by the increase in oxygen vacancy related defect states, and it is directly proportional to the CO gas sensing activity. These defects acted as the oxygen trap sites which will promote the oxygen adsorption on the surface of ZNRs a...