Search

Copper (Cu) doping is a crucial process to improve the hole concentration in CdTe absorber layer and reduce the back-barrier height for efficient CdTe solar cells. However, excess Cu creates detrimental defects and deteriorates device stability due to its high diffusivity. Here, we introduce a wet chemical method to incorporate Cu in CdTe using a CuCl solution. This approach allows a better control of Cu doping than the conventional method using evaporated Cu. Our investigation shows that the CuCl treatment can significantly improve the overall device performances due to an increased carrier concentration in the CuCl treated CdTe absorber layer. Furthermore, the CuCl treated devices show a longer minority carrier lifetime than the conventional Cu treated devices.

Neuromorphic devices play an important role in neuromorphic systems. Stimulating synaptic phototransistors with light spike paves a new method for manufacturing artificial synapses. In this paper, a synaptic In–Ga–Zn–O phototransistor was fabricated, and the photoresponsivity of the device could be tuned by adjusting the annealing temperature of a solution-processed In–Ga–Zn–O thin film. The photoresponsivity and photocurrent-to-the dark current ratio for the In–Ga–Zn–O phototransistors fabricated at various annealing temperatures were analyzed. More importantly, some basic functions of synaptic phototransistors that exhibit excitatory postsynaptic current, short-term plasticity, paired-pulse facilitation, and multi-level photomemory are demonstrated. The results from this study may help others produce synaptic phototransistors for neuromorphic computing.

Long-term, real-time, and comfortable epidermal electronics are of great practical importance for healthcare monitoring and human-machine interaction. However, traditional physiological signal monitoring confined by the specific clinical sites and unreliability of the epidermal electrodes leads to great restrictions on its application. Herein, we constructed a solution-processed submicron (down to 230 nm), free-standing, breathable sandwich-structured hybrid electrode composed of a silver nanowire network with a conductive polymer film, which is conformal, water-permeable, and noninvasive to the skin while achieving good signal acquisition ability. The free-standing hybrid electrode is prepared

Thin-film transistors (TFTs) made of metal oxide semiconductors are now increasingly used in flat-panel displays. Metal oxides are mainly fabricated via vacuum-based technologies, but solution approaches are of great interest due to the advantages of low-cost and high-throughput manufacturing. Unfortunately, solution-processed oxide TFTs suffer from relatively poor electrical performance, hindering further development. Recent studies suggest that this issue could be solved by introducing a novel heterojunction strategy. This article reviews the recent advances in solution-processed heterojunction oxide TFTs, with a specific focus on the latest developments over the past five years. Two of the most prominent advantages of heterostructure oxide TFTs are discussed, namely electrical-property modulation and mobility enhancement by forming 2D electron gas. It is expected that this review will manifest the strong potential of solution-based heterojunction oxide TFTs towards high performance and large-scale electronics.

The amalgamation of thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) properties, term AIE-TADF, is a promising strategy to design novel robust luminescent materials. Herein, we transform 2,3,4,5,6-penta(9H-carbazol-9-yl)benzonitrile (5CzBN) from an ACQ molecule to AIEgens by simply decorating a 5CzBN core with alkyl chain-linked spirobifluorene dendrons. By increasing the number of flexible dendrons, these materials can not only show obvious AIE-TADF characteristics and uniform film morphology, but also exhibit better resistance to isopropyl alcohol, which are beneficial to the fully solution-processed OLEDs. Notably, 5CzBN-PSP show great device efficiency with external quantum efficiency (EQE), current efficiency and power efficiency of 20.1%, 58.7 cd A-1 and 46.2 lm W-1, respectively, which achieved record-breaking efficiency in solution-processed nondoped OLEDs based on AIE emitters. It demonstrates a general approach to explore new efficient emitters by the marriage of AIE and TADF what could potentially improve their performance in various areas.

Construction of core–dendron TADF emitters systematically: changing the behaviour of chromophores from aggregation-caused quenching to aggregation induced emission to develop high-performance fully solution-processed nondoped OLEDs., The amalgamation of thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) properties, termed AIE-TADF, is a promising strategy to design novel robust luminescent materials. Herein, we transform 2,3,4,5,6-penta(9H-carbazol-9-yl)benzonitrile (5CzBN) from an ACQ molecule into an AIEgen by simply decorating the 5CzBN core with alkyl chain-linked spirobifluorene dendrons. By increasing the number of flexible dendrons, these materials can not only show obvious AIE-TADF characteristics and uniform film morphology, but can also exhibit better resistance to isopropyl alcohol, which are beneficial to fully solution-processed OLEDs. Notably, 5CzBN-PSP shows great device efficiency with an external quantum efficiency (EQE), current efficiency and power efficiency of 20.1%, 58.7 cd A–1 and 46.2 lm W–1, respectively and achieved record-breaking efficiency in solution-processed nondoped OLEDs based on AIE emitters. This work demonstrates a general approach to explore new efficient emitters by the marriage of AIE and TADF which could potentially improve their performance in various areas.

In developing low-power electronics, low-voltage transistors have been intensively investigated. One of the most important findings is that some high-k oxide gate dielectrics can lead to remarkable...

Organic electronics with π-conjugated organic semiconductors are promising candidates for the next electronics revolution. For the conductive channel, the large-area two-dimensional (2D) crystals of organic semiconductors (2DCOS) serve as useful scaffolds for modern organic electronics, benefiting not only from long-range order and low defect density nature but also from unique charge transport characteristic and photoelectrical properties. Meanwhile, the solution process with advantages of cost-effectiveness and room temperature compatibility is the foundation of high-throughput print electrical devices. Herein, we will give an insightful overview to witness the huge advances in 2DCOS over the past decade. First, the typical influencing factors and state-of-the-art assembly strategies of the solution-process for large-area 2DCOS over sub-millimeter even to wafer size are discussed accompanying rational evaluation. Then, the charge transport characteristics and contact resistance of 2DCOS-based transistors are explored. Following this, beyond single transistors, the p–n junction devices and planar integrated circuits based on 2DCOS are also emphasized. Furthermore, the burgeoning phototransistors (OPTs) based on crystals in the 2D limits are elaborated. Next, we emphasized the unique and enhanced photoelectrical properties based on a hybrid system with other 2D van der Waals solids. Finally, frontier insights and opportunities are proposed, promoting further research in this field., The advanced assembly strategies for large-area, two-dimensional crystals of organic semiconductors over sub-millimeter even to wafer size, electrical integrated transistors, as well as their burgeoning photoelectrical devices are discussed in this outlook.

The comparison of solution processed organic photovoltaics with two roll-to-roll coated electron transport layers (ETL), as well as printed grid or solid back electrodes provides insight into the future of R2R fabricated architectures. The variation in performance of the R2R slot-die coated zinc oxide (ZnO) versus the tin oxide (SnO2), showed a clear dependence on the spectrum of the illumination source. It was found that under indoor light conditions (200-1000 lux LED and fluorescent sources) the SnO2 outperformed the ZnO with highest efficiencies near 13% and 10% respectively. This is in contrast to results obtained under 1 Sun (AM 1.5) in which the cells fabricated with a ZnO ETL had a higher power conversion efficiency than those prepared with SnO2. The results also confirm the significance of the layout of the printed silver back contact; in which cells with the grid structure outperformed those with full coverage by approximately 35% for ZnO and just under 10% for SnO2 (all light conditions). The combination of a R2R coating and S2S printing process to prepare modules with 8 cells in series (PET/ITO/SnO2/PV2001:PCBM/PEDOT:PSS/silver grid) resulted in a PCE of 13.4% under indoor office light conditions.

Flexible perovskite solar cells (PSCs) have received increasing attention in wearable and portable devices over the past ten years. The low-temperature process of electron transport layer plays a key role in fabricating flexible PSCs. In this paper, we improve the performance of flexible PSCs by controlling the thermodynamic procedure in the low-temperature annealing process of solution-processed TiO2 layers and modulating the precursor concentration of (6,6)-phenyl c61 butyric acid methyl ester (PC61BM) deposited on fluorine-doped tin oxide (FTO)/TiO2 substrate. The results show that slowing down evaporation rate of residual solvent and adopting PC61BM of appropriate precursor concentration are confirmed to be effective methods to improve the performance of flexible PSCs. We also demonstrate carbon electrode-based flexible PSCs. Our work expands the feasibility of low temperature process for the development of flexible perovskite photodetectors and light-emitting diodes, as well as flexible PSCs.

Solution-processed solar cells are appealing because of the low manufacturing cost, the good compatibility with flexible substrates, and the ease of large-scale fabrication. Whereas solution-processable active materials have been widely adopted for the fabrication of organic, dye-sensitized, and perovskite solar cells, vacuum-deposited transparent conducting oxides (TCOs) such as indium tin oxide, fluorine-doped tin oxide, and aluminum-doped tin oxide are still the most frequently used transparent electrodes (TEs) for solar cells. These TCOs not only significantly increase the manufacturing cost of the device, but also are too brittle for future flexible and wearable applications. Therefore, developing solution-processed TEs for solar cells is of great interest. This paper provides a detailed discussion on the recent development of solution-processed TEs, including the chemical synthesis of the electrode materials, the solution-based technologies for the electrode fabrication, the optical and electrical properties of the solution-processed TEs, and their applications on solar cells.

In this work, high-performance four-terminal solution-processed tandem solar cells were fabricated by using dye-sensitized solar cells (DSSCs) as top-cells and lead sulfide (PbS) colloidal quantum dot solar cells (CQDSCs) as bottom-cells. For dye-sensitized top-cells, three different dye combinations were used while the titanium dioxide (TiO2) scattering layer was removed to maximize the transmission. For the PbS bottom-cells, quantum dots with different sizes were compared. Over 12% power conversion efficiency has been achieved by using the XL dye mixture and 890 nm PbS QDs, which shows a significant efficiency enhancement when compared to single DSSC or CQDSC subcells.

The KIT authors are part of the Cluster 3D Matter Made To Order under Germany's Excellence Strategy (3DMM2O – EXC-2082 –390761711), which has been funded by the German Research Foundation. This work was supported, in part, by the Cooperative Research Center (Sonderforschungsbereich SFB 1176) “Molecular Structuring of Soft Matter”. This work was partly supported by JSPS KAKENHI grant nos. 17H01231 and 17J09631, and by the International Joint Usage/Research Centre (iJURC) at the Institute for Chemical Research (ICR), Kyoto University, Japan. The St Andrews authors thank EU horizon 2020 Grant Agreement No. 812872 (TADFlife) for funding. EZ-C acknowledge the International Collaborative Research Program of iJURC/ICR, Kyoto University (Grant No. 2020-37). We report a new emitter 3,4,5-3TCz-TTT based on a tris(triazolo)triazine acceptor that shows thermally activated delayed fluorescence and cross-compare its performance with the recently reported analogue, 3DMAC-TTT. These compounds show blue emission and delayed fluorescence with delayed lifetimes on the order of milliseconds. Solution-processed organic light-emitting diodes achieving maximum external quantum efficiencies, EQEmax, of 5.8% for 3,4,5-3TCz-TTT and 11.0% for 3DMAC-TTT. Publisher PDF

Zn(II) coordination compounds with asymmetric salicylidene ligands in poly[9,9-dioctylfluorenyl-2,7-diyl] (PFO) composites were used for all-solution-processable white organic light-emitting diode ...

Hydrophobic coatings have the ability to promote dropwise condensation on metal surfaces. In this work, reduced graphene oxide coatings are fabricated by dip coating copper substrates into a graphene oxide colloidal suspension, followed by thermal reduction. The formation of reduced graphene oxide is demonstrated by Raman and X‐ray photoelectron spectroscopy characterizations, while scanning electron microscopy, atomic force microscopy and dynamic water contact angle analyses are employed to verify the morphology and the wettability of the coatings. The prepared coatings demonstrate applicability in the promotion of dropwise condensation of pure steam, with an 8‐fold enhancement of the heat transfer coefficient compared to film‐wise condensation. In addition, durability of the reduced graphene oxide coatings of more than 100 hours in the tested condition is reported.

Binary compound antimony sulfide (Sb2S3) with its nontoxic and earth-abundant constituents, is a promising light-harvesting material for stable and high efficiency thin film photovoltaics. The intrinsic quasi-1D (Q1D) crystal structure of Sb2S3 is known to transfer photogenerated carriers rapidly along the [hk1] orientation. However, producing Sb2S3 devices with precise control of [hk1] orientation is challenging and unfavorable crystal orientations of Sb2S3 result in severe interface and bulk recombination losses. Herein, in situ vertical growth of Sb2S3 on top of ultrathin TiO2/CdS as the electron transport layer (ETL) by a solution method is demonstrated. The planar heterojunction solar cell using [hk1]-oriented Sb2S3 achieves a power conversion efficiency of 6.4%, performing at almost 20% higher than devices based on a [hk0]-oriented absorber. This work opens up new prospects for pursuing high-performance Sb2S3 thin film solar cells by tailoring the crystal orientation. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) L.H.W. and S.H. acknowledge the funding support from the CREATE Programme under the Campus for Research Excellence and Technological Enterprise (CREATE), which was supported by the National Research Foundation, Prime Minister’s Office, Singapore; and the Ministry of Education (MOE) Tier 2 Project (MOE2016-T2-1-030). T.C.S and M.F. acknowledge the financial support from Nanyang Technological University start-up grant M4080514.

Narrow-band deep-blue (emission peak < 460 nm) TADF emitters are in demand for commercial OLED display applications, yet the development of efficient emitters with low efficiency roll-off is very challenging. To address this issue, herein, we studied carbazole–naphthyridine (donor–acceptor)-based blue-emitting TADF compounds, which were designed by using both the H-bonding and sterically controlled charge-transfer (CT) interactions between D and A units. Methyl substitution employed at the first position of t-butyl-carbazole donors was found to affect CT strength and consequently the TADF properties of the studied compounds, enabling a significant reduction of delayed fluorescence lifetime (down to 3.1 μs) and enhancement of reverse intersystem crossing rate (up to 106 s−1). The naphthyridines were demonstrated to hold great potential as deep-blue TADF emitters suitable for both vacuum- and solution-processed TADF OLEDs. The optimized devices with 7 wt% naphthyridine emitter in a weakly polar mCP host delivered external quantum efficiencies (EQEs) of up to ∼17.6% and ∼13.5% for vacuum- and solution-processed OLEDs, respectively. Unsubstituted naphthyridine exhibited deep-blue (λmax < 460 nm) and narrow-band (FWHM = 66 nm) electroluminescence, whereas the more twisted methyl-substituted compound expressed broader band (FWHM > 80 nm) sky-blue (λmax ≈ 480 nm) emission. The demonstrated emitters are among the best-performing conventional D–A-type blue/deep-blue TADF emitters in terms of EQE and efficiency roll-off properties of their devices.

Searching new light-absorbing materials to replace toxic lead halide in solar cells is very important and highly desirable. In this research, we firstly demonstrated that tellurium iodide (TeI4 ) could be used as a light-absorbing material in solar cells due to its suitable optical band gap and the active lone-pair electron orbital in Te4+ . The best power conversion efficiency (PCE=3.56%) was achieved with a concentration of 0.9 M TeI4 in DMF:DMSO (4 : 1, v,v) without any heat treatment or antisolvent dripping. Our study indicates the promising potential of TeI4 for photovoltaic and optoelectronic applications. Ministry of Education (MOE) Q.Z.acknowledges financial support from AcRF Tier 1 (RG 111/17,RG 2/17,RG 114/16,RG 8/16) and Tier 2 (MOE2017-T2-1-021 and MOE2018-T2-1-070),Singapore.

Wearable medical devices offer a great opportunity to monitor human vital signs to improve healthcare. The use of printing technologies is a promising approach to fabricate the wearables. An encapsulation must be applied to achieve longterm stability and reliability of the printed wearables. In this paper, we discuss the encapsulation requirements of printed wearable medical devices. Different encapsulation approaches are illustrated by means of various examples. Thereby, the focus lies upon solution-processed encapsulation, including the compatible materials and printing technologies.

Colloidal quantum dot solar cells have drawn great attention in the past decade due to their easy synthesis, tunable bandgaps and low cost. However, the quantum dots’ low absorbance together with limits placed on the thickness of the absorbing layer due to poor transport properties is hindering the development of quantum dot solar cells. In this research, for further developing quantum dot solar cells, a tandem solar cell strategy was utilised to address the above problem. A tandem solar cell stacks materials with different bandgaps to more efficiently convert the energy of a wider range of photons to electricity for higher solar cell efficiency. This project developed high performance monolithic tandem solar cells based on PbS colloidal quantum dots. Firstly, single-junction colloidal quantum dot cells were optimised as the building blocks of the tandem cells. MgCl2 passivated ZnO-NP electron transporting layers were applied to improve single-junction colloidal quantum dot cells by increasing both fill factor FF and short circuit current Jsc. Significant efficiency improvement has been observed based on single-junction PbS solar cells. Secondly, an optical modelling tool was created for the first time to simulate tandem colloidal quantum dot solar cells. This model could offer exact simulation on photon absorbance and current generation in tandem cells’ functional layers. The model provided very instructive and quite essential guidance for designing the tandem cell structure and experimental works of fabricating quantum dot tandem cells. Thirdly, based on improved single-junction PbS solar cell and an established directive model, high performance tandem colloidal quantum dot solar cells were successfully fabricated with different interlayers of both Au and ITO. A graded band alignment employing both ZnO-doping and quantum dot size tuning has been applied to further improve tandem cell performance. Due to improved carriers extraction, this strategy successfully pushed the efficiency of a tandem quantum dot solar cell to be around 7%.

Amorphous oxide semiconductors have drawn considerable attention as a replacement for ubiquitous silicon based technologies. By virtue of their flexible substrate compatibility and transparency, amorphous metal oxide semiconductor (AOS) thin film transistors (TFTs) are being explored in emerging flexible/transparent technologies. However, rapid advances in such technologies require the development of high-performance thin film transistors, which can be fabricated at low processing temperatures. In this review paper, we discuss the recent progress made in n-type semiconductor TFTs activated at low temperatures both on rigid and flexible substrates with a focus on the replacement of conventional high temperature annealing. Several low temperature processing approaches that have been reported in both vacuum deposited and solution processed n-type metal oxide semiconductor based thin film transistors are evaluated, with an emphasis on some novel techniques which can effectively modulate the electronic properties of the n-type metal oxide semiconductor systems at low temperatures. The final part of this review draws conclusions and discusses the outlook for future research efforts in achieving low temperature activated high performance n-type TFTs. Ministry of Education (MOE) Accepted version

Large open-circuit voltage (VOC) deficit has been widely regarded as the main hindrance to realize the full potential of the low-cost and environmental-friendly Cu2ZnSnS4 (CZTS) solar cell. Alloying and doping are seen as promising pathways to reduce the harmful defects in CZTS and the VOC deficit. In this study, we demonstrate the fabrication of double-layer CZTS alloyed with silver and doped with potassium (ACZTS-KCZTS). The device shows an increase in VOC relative to its corresponding Shockley–Queisser limit (VOC/VOC,SQ) and improvement of short-circuit current (JSC) compared to the CZTS reference to realize an optimized active area device efficiency of 8.24%. The avoidance of void formation and improved carrier collection in the bulk and interface region contributed to performance improvement. This double-layer configuration could be a viable route for codoping using other elements. Ministry of Education (MOE) Accepted version The authors would like to acknowledge the funding support from the CREATE Programme under the Campus for Research Excellence and Technological Enterprise (CREATE), which is supported by the National Research Foundation, Prime Minister's Office, Singapore; and the Ministry of Education (MOE) Tier 2 Project (MOE2016-T2-1-030).

Manufacturing commercially viable perovskite solar cells still requires appropriate low‐temperature and scalable deposition processes to be developed. While α‐phase FAPbI3 has higher thermal stability and broader absorption than MAPbI3, there still is no report of a pure α‐phase FAPbI3 perovskite film obtained by a scalable printing method. Moreover, spontaneous conversion of the α‐phase to non‐perovskite δ‐phase under ambient conditions poses a serious challenge for practical applications. Herein, a scalable and fully solution based printing method for the fabrication of pure α‐phase FAPbI3 perovskite solar cells is reported. Through adding N‐methyl pyrrolidone and methylammonium chloride to the dimethylformamide based precursor solution to control the crystallization, and vacuum or air‐flow assisted film drying, pure α‐FAPbI3 phase is obtained by doctor blading. The resulting α‐FAPbI3 film is highly stable, with no δ‐FAPbI3 phase being formed even after keeping it in an ambient atmosphere over a period of 200 days without encapsulation. In addition, a fully solution processed PSC with a PCE of 16.1% is processed by the vacuum assisted method, and 17.8% by the air‐flow assisted method. Replacing silver with a printed carbon electrode provides a stable PCE up to 15% for the vacuum assisted and 16.4% for the air‐flow assisted method, which is the highest performance of FAPbI3 solar cells to date. Compared with MAPbI3, the fully printed FAPbI3 perovskite devices exhibit a remarkable thermal stability in humid atmospheres which makes them a promising candidate for scalable production and commercialization.

Surface recombination of photogenerated carriers turned to be critical issues against the realization of high-performance nanowire-based solar cells. To overcome it, the strategy toward passivating nanowire surfaces was essential where the improvement of minority carrier lifetime was identified in recent years; instead, the examinations of optical management as well as charge-transfer resistance at heterojunction were still limited. In this study, we herein investigated the facile, inexpensive and reliable HNO3-based chemical passivation that directly introduced SiOx coating on Si nanowires. By adjusting the oxidation durations, the cell performance exhibited the improved conversion efficiency with more than 39% of efficiency enhancement than reference cells. Impacts of light harvesting and charge separation characteristics on cell performances were in-depth envisioned.

Despite the rapid development in quantum-dot light-emitting diodes (QD-LEDs) with a single junction, it remains a big challenge to make tandem QD-LEDs with high performance. Here, we report solution-processed double-junction tandem QD-LEDs with a high external quantum efficiency of 42.2% and a high current efficiency of 183.3 cd A

Optical green emitting microresonators with high values of nonlinearity are desired for high optical up-conversion energy storage and lasing applications. Here we report on the synthesis of benzyla...

Phosphorescent organic light-emitting diodes (PhOLEDs) have attracted tremendous attention recently but still suffer serious efficiency roll-off at high luminance, which will significantly limit th...

Unlike ordinary organic field-effect transistors (OFETs), saturation current is hardly to be found in vertical OFETs (VOFETs). Moreover, the fabrication process of patterned sourced for VOFETs is quite complex. In this current work, a simple solution processed VOFET with directly deposited intermediate silver source electrode has been demonstrated. The VOFET exhibits a high leakage current that induces an inversion polarity of its transistor behavior. Interestingly, a well-defined saturation current was observed in the linear scale of transfer characteristic. The VOFET operated with high-current density >280 mA/cm2 at Vd = 5 V. Overview potential of the fabricated device in display application is also presented. This preliminary work does open-up a new direction in VOFET fabrication and their application.

To utilize the potential of small-molecule-based organic solar cells, proper designs of the photoactive materials which result in reasonable performance in a halogen-free solvent system and thickness tolerance over a range are required. One of the best approaches to achieve these requirements is via the molecular engineering of small-molecule electron donors. Here, we have modified a previously reported dithienobenzodithiophene (DTBDT)-based small molecule (SM1) via the dimerization approach, that is, the insertion of an additional DTBDT into the main backbone of the small molecule (SM2). An SM1-based photoactive film showed severe pinhole formation throughout the film when processed with a halogen-free o-xylene solvent. On the other hand, the modified small-molecule SM2 formed an excellent pinhole-free film when processed with the o-xylene solvent. Because of the dimerization of the DTBDT in the SM2 core, highly crystalline films with compact lamellae and an enhanced donor/acceptor interdigitation were formed, and all of these factors led to a high efficiency of 8.64% with chloroform and 8.37% with the o-xylene solvent systems. To the best of our knowledge, this study represents one of the best results with the SM donor and fullerene derivative acceptor materials that have shown the device performance with halogen-free solvents.

We designed and synthesized a dibenzothiphene dioxide-based homopolysiloxane, PDBTSi, and a carbazole-dibenzothiophene dioxide alternating copolysiloxane, PCzSi-alt-PDBTSi, respectively. Both PDBTSi and PCzSi-alt-PDBTSi possess an improved solubility, good film-forming ability and extremely high thermal stability due to introduction of polysiloxane main chains. Meanwhile, PDBTSi and PCzSi-alt-PDBTSi exhibit high triplet energy levels of 2.95 eV and 3.05 eV, respectively. Furthermore, PDBTSi possesses good electron-transporting property with an electron mobility of 1.02×10-4 cm2 V-1 s-1 and a relatively balanced hole mobility of 8.76×10-5 cm2 V-1 s-1 . In contrast, PCzSi-alt-PDBTSi exhibits an electron mobility of 4.65×10-5 cm2 V-1 s-1 and a hole mobility of 1.17×10-4 cm2 V-1 s-1 . Therefore, our results here provide a feasible strategy to obtain solution-processed polysiloxane materials with high and balanced electron- and hole-transporting properties.

We report a nonvolatile-memory device based on solution-processed Hf-doped ZnO (ZnO:Hf) thin-film transistors (TFTs) fabricated by inserting SiO2 microparticles (MPs) and nanoparticles (NPs) as a charge trapping medium. The transfer characteristics of ZnO:Hf TFT devices inserted with SiO2 particles showed a large clockwise hysteresis behavior owing to charge carrier trapping capability. Both memory devices exhibited a highly programmable memory window during the program/erase operation, which can be attributed to charge carrier trapping and de-trapping in SiO2 particles. Particularly, the memory device with SiO2 NPs revealed a larger memory window over 25 V than that with MPs. Furthermore, the fabricated memory devices showed remarkably long-term retention characteristics and the ON/OFF current ratio greater than 104.

We reported the low-temperature high performance IGZO TFTs by solution processing. The influence of IGZO composition over broad range on thin films and devices properties were investigated by a wide range of characterization techniques. The schematic of TFT solution-processed IGZO TFTs mobility with different compositions has been obtained. In order to achieve decent TFT performance, the In content should be much high for solution-processed IGZO TFTs. The optimal solution-processed IGZO TFTs with In:Ga:Zn = 5:1:1 composition exhibited a large mobility of 9.1 cm2 V−1 s−1, low subthreshold swing of 0.22 V/decade, and high on/off ratio of 106 at 300 °C processing temperature.

In this work, we demonstrate the chemical optimization of benzo[1,2-b:4,5-b′]dithiophene (BDT)-5,6-difluorobenzo-[2,1,3]thiadiazole (FBT) D-A alternating copolymer for obtaining the efficient polymeric donors for the environment-friendly solution processed polymer solar cells (PSCs). Three polymers PBTF, PBTTF-C6 and PBTTF-H, in which one or two alky thiophene units are inserted into the backbone of BDT-FBT alternating copolymer, present much different performances either in the PSCs processed from halogenated solvent and additive or in the PSCs processed from non-halogenated solvent and additive. With an alky thiophene and a bare thiophene as the spacer, PBTTF-H performs best among the three. Especially when the devices processed from 1,2,4-trimethylbenzene and diphenyl ether, in which the highest PCE of 6.80% is achieved with a VOC of 0.77 V, a JSC of 13.67 mA cm−2 and a FF of 64.2%. We think these results will cast light on developing new polymeric donors of the green-solvent-processed PSCs.

Fullerenes have attracted considerable interest as an electron-transporting layer in perovskite solar cells. Fullerene-based perovskite solar cells produce no hysteresis and do not require high-temperature annealing. However, high power conversion efficiency has been only achieved when the fullerene layer is thermally evaporated, which is an expensive process. In this work, the limitations of a solution-processed fullerene layer have been identified as high crystallinity and the presence of remnant solvents, in contrast to a thermally deposited C60 film, which has low crystallinity and no remaining solvents. As a solution to these problems, a mixed C60 and C70 solution-processed film, which exhibits low crystallinity, is proposed as an electron-transporting layer. The mixed-fullerene-based devices produce power conversion efficiencies as high as that of the thermally evaporated C60-based device (16.7%) owing to improved fill factor and open-circuit voltage. In addition, by vacuum-drying the mixed fulleren...

Despite their importance for future applications, the operational electrical stability of organic thin-film transistors is far from being understood. Even in the most stable organic field-effect transistors (OFETs) operated under vacuum, a hitherto unknown source leads to bias stress. Here, we investigate the electrical characteristics and operational stability of a high-performance diketopyrrolopyrrole-alt-terthiophene organic semiconductor. Even though the OFETs are characterized by a high mobility of 3 cm2 V–1 s–1 and trap-free transport, the threshold voltage shift in all stress modes remains sensitive to the presence of water even when operating devices in high vacuum. Exponential fitting from current bias-stress measurement up to 500 000 s showed a bias-voltage shift of

In perovskite solar cells , inorganic hole transport materials have attracted intense attention because of the properties of high chemical stability, hole mobility and low cost. However, most of the inorganic hole conductors exhibit low performance compared with organic hole transport materials. In this study, a facile solution method was developed to prepare a V 2O5 film combined with P3CT-K thus forming a bilayer structure as hole transport layers in inverted CH3NH3PbI3 solar cells. It was found that the hole transport bilayer not only increased the rate of extraction charge but also reduced charge recombination compared with the P3CT-K only based device. As a result, the power conversion efficiency of inverted CH3NH3PbI3 solar cells based on the bilayer was boosted up to the optimal value of 19.7% (average value: 19.0%). Furthermore, the device maintained an efficiency of more than 86% through one-month follow-up, in which the dense and hydrophobic V2O5 film accounted for the improved device stability.

Low-temperature solution-processed SnO2 as a promising electron-transport material for planar perovskite solar cells (PSCs) has attracted particular attention because of its outstanding properties such as high optical transparency or high electron mobility. However, low-temperature sol-gel processes used in the synthesis are inevitably affected by the humidity of the atmosphere, which results in a wide distribution in the performance of the prepared PSCs owing to the inability to control crystallinity and defects. Herein, a highly crystalline SnO2 film is synthesized using a simple water bath post-treatment, which can remove the surface residuals of SnCl4 on the SnO2 films, which is beneficial for the interface charge transport from the perovskite to the SnO2 electron-transport layer. An improved performance of the PSCs can be easily obtained applying this treatment, giving rise to a high power conversion efficiency (PCE) of 19.17 %, much higher than that of the pristine SnO2 -based device (17.59 %). Most importantly, the reproducibility of the devices has been greatly improved, independent of the environmental humidity. Therefore, the enhanced crystallinity of SnO2 has shown promise for future commercial PSC applications: 5 cm×5 cm PSC modules have achieved a PCE of 16.16 %.

Poly( N, N'-bis(4-butylphenyl) N, N'-bis(phenyl)benzidine) (poly-TPD) and poly(9-vinylcarbazole) (PVK) are both traditional hole transport layers (HTLs) in quantum dot light emitting diodes (QLEDs). Nevertheless, the low highest occupied molecular orbital of poly-TPD and poor hole mobility of PVK always result in poor performance of QLEDs when individually used as HTLs. Unfortunately, fabricating stepwise HTLs with poly-TPD and PVK faces technical problems until now. We demonstrate an effective method to construct the stepwise poly-TPD and PVK HTLs by utilizing the technique of hot spin-coating PVK in m-xylene on poly-TPD film. During this hot spin-coating process, the underlying poly-TPD remains unwashed and undamaged, benefiting the all-solution-processed QLED fabrication. The optimized all-solution-processed QLED with stepwise poly-TPD and PVK HTLs shows a maximum external quantum efficiency (EQE) of 15.3% and a maximum luminance of 17 110 cd/m

Organic-inorganic hybrid thin films were fabricated using the sol-gel method and applied to multi-layer organic light-emitting diodes (OLEDs) as an active layer. A polymer emissive material poly (9,9-dioctyl-fluorene-co-N-4-butylphenyl-diphenylamine) (TFB) was solved in a sol-gel reaction accelerator perhydropolysilazane (PHPS). The PHPS solution turned into SiO2 by humidity treatment. Thus, the TFB:PHPS solution became SiO2 thin films in which the organic emissive material TFB was dispersed. All the organic layers of OLEDs can be fabricated using solution-process because the organic-inorganic hybrid active layer is not soluble with the adjacent organic layers. Consequently, we successfully fabricated quintuple-layer OLEDs consisting of the following five organic films: hole-injection, hole-transporting, active (organic-inorganic hybrid) electron-transporting, and electron-injection layers. Electroluminescence (EL) was successfully observed.

In this study, solution-processed blue organic light-emitting diodes (OLEDs) were constructed by employing POBPCz as a bipolar host material with a high triplet of 3.01 eV and 2CzPN as the blue TADF emitter. A maximum EQE of 12.9% was realized in the blue TADF OLEDs, along with a satisfactory CIE coordinate of (0.19, 0.37). These results were among the best ones for the 2CzPN-based solution processed blue OLEDs. Moreover, solution-processed white OLEDs (WOLEDs) with a single-emitting layer were fabricated by Ir(MDQ)2 (acac) as the orange-red iridium complex. The optimized WOLEDs could achieve a maximum EQE of 12.4%, as well as the stable electroluminescence spectra. Notably, the white-light emission was achieved by the incomplete energy transfer from the blue TADF emitter of 2CzPN to the orange-red emitter of Ir (MDQ)2 (acac) via Forster energy transfer (FRET) process.