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Charge injection and transport layers with optimum carrier transport properties are essential for stable and efficient organic light-emitting diode (OLED) devices. Herein, we report two tetraphenylethylene-diphenylamine derivatives, TPOMe and TPOSt having four and two methoxy substituents, respectively, and explore their potential as solution-processable hole injection layers (HILs) for OLEDs. Standard, Alq3-based green OLEDs with a simple device design were used to demonstrate the properties of the synthesized HILs, in comparison with a commercially available standard HIL, m-MTDATA. TPOMe-based device exhibited a current efficiency of 4.2 cd A−1, while TPOSt-based device showed 3.81 cd A−1 at 10 mA cm−2. Both the above devices showed better performance compared to a control device fabricated with the standard HIL, m-MTDATA, which showed a relatively lower current efficiency value (1.70 cd A−1 at 10 mA cm−2). Similarly, the maximum external quantum efficiency (EQE) of TPOMe (1.77%) and TPOSt (1.55%) were higher than that of the m-MTDATA-based device (1.40%). Although m-MTDATA device has better luminance and hole mobility compared to TPOMe and TPOSt devices, the optimum charge balance in the latter devices leads to better current efficiency and EQE. [ABSTRACT FROM AUTHOR]

The fabrication of optoelectronic devices using low‐cost inkjet printing techniques is a topic of great interest to the scientific and industrial community and represents a step toward the full deployment of solution‐processable organic light emitting diodes (OLEDs), particularly for commercial lighting and signaling applications. Herein, the inkjet printing of tBuCzDBA (9,10‐bis(4‐(3,6‐di‐tert‐butyl‐9H‐carbazol‐9‐yl)−2,6‐dimethylphenyl)−9,10‐diboraanthracene) is reported, a high‐performing thermally activated delayed fluorescence (TADF) emitter for OLEDs. Optimizing the surface tension values of the ink formulations and the associated wetting behavior are crucial parameters for achieving a uniform and homogeneous printed thin film. In particular, it is observed that using a proper mixture of solvents with different surface tensions, it is possible to generate Marangoni flows inside the drop, which triggers a very fast drying process, ensuring optimized morphological and optical properties in the inkjet printed tBuCzDBA‐based film. OLEDs exploiting this film as an emissive layer are then fabricated, achieving a maximum luminance of 32 000 cd m−2, a current efficiency of 27.5 cd A−1, and an external quantum efficiencyof 10%. To the best of the knowledge, this is the highest efficiency reported to date for self‐hosted TADF inkjet‐printed OLEDs. [ABSTRACT FROM AUTHOR]

Abstract The fabrication of optoelectronic devices using low‐cost inkjet printing techniques is a topic of great interest to the scientific and industrial community and represents a step toward the full deployment of solution‐processable organic light emitting diodes (OLEDs), particularly for commercial lighting and signaling applications. Herein, the inkjet printing of tBuCzDBA (9,10‐bis(4‐(3,6‐di‐tert‐butyl‐9H‐carbazol‐9‐yl)−2,6‐dimethylphenyl)−9,10‐diboraanthracene) is reported, a high‐performing thermally activated delayed fluorescence (TADF) emitter for OLEDs. Optimizing the surface tension values of the ink formulations and the associated wetting behavior are crucial parameters for achieving a uniform and homogeneous printed thin film. In particular, it is observed that using a proper mixture of solvents with different surface tensions, it is possible to generate Marangoni flows inside the drop, which triggers a very fast drying process, ensuring optimized morphological and optical properties in the inkjet printed tBuCzDBA‐based film. OLEDs exploiting this film as an emissive layer are then fabricated, achieving a maximum luminance of 32 000 cd m−2, a current efficiency of 27.5 cd A−1, and an external quantum efficiencyof 10%. To the best of the knowledge, this is the highest efficiency reported to date for self‐hosted TADF inkjet‐printed OLEDs.

Unencapsulated organic solar cells are prone to severe performance losses in the presence of moisture. Accelerated damp heat (85 °C/85% RH) studies are presented and it is shown that the hygroscopic hole-transporting PEDOT:PSS layer is the origin of device failure in the case of prototypical inverted solar cells. Complementary measurements unveil that under these conditions a decreased PEDOT:PSS work function along with areas of reduced electrical contact between active layer and hole-transport layer are the main factors for device degradation rather than a chemical reaction of water with the active layer. Replacements for PEDOT:PSS are explored and it is found that tungsten oxide (WO3) or phosphomolybdic acid (PMA)--materials that can be processed from benign solvents at room temperature--yields comparable performance as PEDOT:PSS and enhances the resilience of solar cells under damp heat. The stability trend follows the order PEDOT:PSS<3

High‐quality hosts are indispensable for simultaneously realizing stable, high efficiency, and low roll‐off blue solution‐processed organic light‐emitting diodes (OLEDs). Herein, three solution processable bipolar hosts with successively reduced triplet energies approaching the T1 state of thermally activated delayed fluorescence (TADF) emitter are developed and evaluated for high‐performance blue OLED devices. The smaller T1 energy gap between host and guest allows the quenching of long‐lived triplet excitons to reduce exciton concentration inside the device, and thus suppresses singlet‐triplet and triplet‐triplet annihilations. Triplet‐energy‐mediated hosts with high enough T1 and better charge balance in device facilitate high exciton utilization efficiency and uniform triplet exciton distribution among host and TADF guest. Benefited from these synergetic factors, a high maximum external quantum efficiency (EQEmax) of 20.8%, long operational lifetime (T50 of 398.3 h @ 500 cd m−2), and negligible efficiency roll‐off (EQE of 20.1% @ 1000 cd m−2) are achieved for bluish‐green TADF OLEDs. Additionally introducing a narrowband emission multiple‐resonance TADF material as terminal emitter to accelerate exciton dynamic and improve exciton utilization, a higher EQEmax of 23.1%, suppressed roll‐off and extended lifetime of 456.3 h are achieved for the sky‐blue sensitized OLEDs at the same brightness. [ABSTRACT FROM AUTHOR]

Herein, solution‐processed indium gallium zinc oxide (IGZO) thin‐film transistors (TFTs) with a bilayer structure are investigated by embedding an ultrathin layer of indium zinc oxide (IZO) between the gate dielectric and IGZO film. The optimized IGZO/IZO bilayer TFTs exhibit a high field‐effect mobility (μFE) of 8.3 cm2 V−1 s−1, and the bias‐stress stability of the bilayer TFTs is greatly improved compared with that of the single‐layer IGZO devices. In addition, temperature‐dependent mobility and VT are investigated to reveal the trap distribution in the bilayer IGZO/IZO and single‐layer IGZO TFTs. Moreover, low‐voltage bilayer TFTs with a high mobility of 10.4 cm2 V−1 s−1 are demonstrated. [ABSTRACT FROM AUTHOR]

The effect of light illumination intensity on the stability of In-Zn-Sn-O (IZTO) thin-film transistors (TFTs) array fabricated by solution processed is investigated. Comparison with positive bias stress, the light illumination suppresses the ${V}_{\text {th}}$ shift under positive bias illumination stress because of the increase in the free electrons induced by the ionized oxygen vacancies in the IZTO channel layer, but transfer characteristics show two-stage degradation under negative bias illumination stress (NBIS). The hump phenomenon is induced after NBIS, and the light illumination intensity is higher, the hump phenomenon becomes more serious. The hump phenomenon is relevant to ionized oxygen vacancies, which act as shallow donor-like states near the conduction-band minimum in IZTO. [ABSTRACT FROM AUTHOR]

Solution‐processed tetraphenyldibenzoperiflanthene (DBP) films are prepared with three popular solvents, including chroloform (CF), chrolobenzene (CB), and dichrolobenzene (ODCB). The absorption and photoluminescence (PL) spectra of the DBP solution and DBP film are investigated. The absorption spectra between the DBP film and DBP solution are similar, whereas the PL spectrum shape of the DBP film and DBP solution is completely different, originating from the DBP molecular aggregation in the film, causing conjugate expansion, which results in dimer luminescence. The DBP donor layer at 32 nm prepared from solvent of CF, CB, and ODCB achieves a power conversion efficiency (PCE) of 1.42%, 0.88%, and 0.48%, respectively. The annealing temperature and DBP thickness are optimized; the 32 nm‐thick active layer annealed at 50 °C achieves the highest performance. The CF‐DBP film represents an interpenetrating network morphology, slightly higher roughness and hole mobility, which may be the main contribution to the relatively higher photocurrent than the CB‐DBP and ODCB‐DBP devices. Herein, a simple guidance for preparing solution‐processed DBP films is provided and simultaneously its application on organic photovoltaic cells (OPVs) is expanded. [ABSTRACT FROM AUTHOR]

As an earth-abundant p-type semiconductor, copper sulfide (Cu2S) is an attractive material for application in photovoltaic devices. However, it suffers from a minority carrier diffusion length that is less than the length required for complete light absorption. Core-shell nanowires and nanorods have the potential to alleviate this difficulty because they decouple the length scales of light absorption and charge collection. To achieve this geometry using Cu2S, cation exchange was applied to an array of CdS nanorods to produce well-defined CdS-Cu2S core-shell nanorods. Previous work has demonstrated single-nanowire photovoltaic devices from this material system, but in this work, the cation exchange chemistry has been applied to nanorod arrays to produce ensemble-level devices with microscale sizes. The core-shell nanorod array devices show power conversion efficiencies of up to 3.8%. In addition, these devices are stable when measured in air after nearly one month of storage in a desiccator. These results are a first step in the development of large-area nanostructured Cu2S-based photovoltaics that can be processed from solution.

An approach based on a solution-based synthesis that produces a thermally stable Ag/oxide/S₂ Te₃ -Te metal-semiconductor heterostructure is described. With this approach, a figure of merit of zT = 1.0 at 460 K is achieved, a record for a heterostructured material made using wet chemistry. Combining experiments and theory shows that the large increase in the material's Seebeck coefficient results from hot carrier filtering.

Abstract Due to their outstanding performance, low cost, ease of fabrication, diverse photonic, and optoelectronic applications, metal halides perovskite have attracted extensive interest in photodetector applications. Currently, devices made by metal oxides, metal sulfides, and 2D materials had achieved good responsivity, but suffered from high dark current, slow response speed, small on-off ratio, and poor stability. Whole performances of these photodetectors are not satisfactory. Here, a lateral perovskite (CH3NH3PbBr3)/Ethanolamine/TiO2 (in ethanol) trilayer photodetector is designed for achieving high performance. EA treatment enhances electron extraction and reduces undesired recombination. This trilayer device shows good performances with low dark current of 1.5 × 10−11 A, high on-off ratio of 2700, high photodetectivity of 1.51 × 1012 Jones, high responsivity of 0.13 A W−1, and high stability, comparative to conventional single layer devices. This work provides the way to improve the performance of metal halide perovskite photodetectors.

Widely investigated thermally activated delayed fluorescence (TADF) can be achieved by intramolecular and intermolecular charge transfer between an electron donor and electron acceptor which corresponds to a TADF material and exciplex, respectively. However, the development of efficient organic light‐emitting diodes (OLEDs) based on an exciplex lags far behind the development of those based on efficient TADF materials. In this work, a novel D‐A type electron donor TPAFPO was designed and synthesized. TPAFPO:PO‐T2T exhibits a small ΔEST of 79 meV and significant delayed emission, demonstrating TADF characteristics. OLEDs based on TPAFPO:PO‐T2T exhibit a low turn‐on voltage of 2.4 V and high an EQE value of 17.0%. Besides, NIR OLEDs utilizing TPAFPO:PO‐T2T as host exhibit a turn‐on voltage of 3.0 V and high EQE of 9.2% with a NIR emission peak at 690 nm. Furthermore, solution‐processed exciplex and NIR devices also can maintain high efficiencies of 15.1% and 8.1%, respectively. [ABSTRACT FROM AUTHOR]

We show that, excellent ambient air stability can be achieved in organic‐inorganic hybrid perovskite thin‐film transistors (TFTs) through low‐temperature, solution processing in ambient air. Combined with their ambipolar nature and low‐voltage drivability, the perovskite TFTs demonstrated here are thus candidates for simple CMOS circuits in low‐cost, large‐area and/or printed displays. [ABSTRACT FROM AUTHOR]

Solution-processed hybrid solar cells have been well developed in the last twenty years due to the advantages of low cost, low material-consuming and simple fabricating technology. However, the performance, stability and film quality of hybrid solar cells need to be further improved for future commercial application (with a lifetime up to 20 years and power conversion efficiency higher than 15%). By combining the merits of organic polymers and nanocrystals (NC), the reasonable design of interface engineering and device architecture, the performance coupled with stability of hybrid solar cells can be significantly improved. This review gives a brief conclusive introduction to the progress on solution-processed organic/inorganic semiconductor hybrid solar cells, including a summary of the development of hybrid solar cells in recent years, the strategy of hybrid solar cells with different structures and the incorporation of new organic hole transport materials with new insight into device processing for high efficiency. This paper also puts forward some suggestions and guidance for the future development of high-performance NC-based photovoltaics. [ABSTRACT FROM AUTHOR]

Layered semiconductors of the IIIA–VIA group have attracted considerable attention in (opto)electronic applications thanks to their atomically thin structures and their thickness‐dependent optical and electronic properties, which promise ultrafast response and high sensitivity. In particular, 2D indium selenide (InSe) has emerged as a promising candidate for the realization of thin‐film field effect transistors and phototransistors due to its high intrinsic mobility (>102 cm2 V−1 s−1) and the direct optical transitions in an energy range suitable for visible and near‐infrared light detection. A key requirement for the exploitation of large‐scale (opto)electronic applications relies on the development of low‐cost and industrially relevant 2D material production processes, such as liquid phase exfoliation, combined with the availability of high‐throughput device fabrication methods. Here, a β polymorph of indium selenide (β‐InSe) is exfoliated in isopropanol and spray‐coated InSe‐based photodetectors are demonstrated, exhibiting high responsivity to visible light (maximum value of 274 A W−1 under blue excitation 455 nm) and fast response time (15 ms). The devices show a gate‐dependent conduction with an n‐channel transistor behavior. Overall, this study establishes that liquid phase exfoliated β‐InSe is a valid candidate for printed high‐performance photodetectors, which is critical for the development of industrial‐scale 2D material‐based optoelectronic devices. [ABSTRACT FROM AUTHOR]

Herein, a 2D α‐In2Se3 nanosheet, a binary III–VI group compound semiconductor, is fabricated by liquid‐phase exfoliation method, and the photoelectric properties of α‐In2Se3 material are investigated in depth. It is found that α‐In2Se3 film exhibits significant conductivity, outstanding optical transmission, and a suitable work function. Combined with its smooth surface and preferable hydrophobicity, α‐In2Se3 film can efficiently facilitate hole transporting in the polymer solar cells (PSCs). Due to the aforesaid advantages, a 2D α‐In2Se3 nanosheet is used as a hole transport layer (HTL) in conventional PSCs for the first time, and a relatively high power conversion efficiency (PCE) of 9.58% is achieved with the structure of ITO/α‐In2Se3/PBDB‐T:ITIC/Ca/Al, which is comparable with poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)‐based devices (9.50%). Interestingly, it is demonstrated that the α‐In2Se3 film possesses excellent thermal stability in the range from room temperature to 280 °C, and a PCE of 9.35% is achieved without annealing treatment of α‐In2Se3 film, which exhibits a great potential of α‐In2Se3 for an annealing‐free approach. Furthermore, the incorporation of α‐In2Se3 HTL also remarkably enhances the long‐term stability of PSCs compared with PEDOT:PSS‐based devices. So, the results show that 2D α‐In2Se3 is a promising candidate to be an efficient and stable hole‐extraction layer. [ABSTRACT FROM AUTHOR]

Xiao-Lin Wang et al., Effect of the Gas Flow Rate in the Focused-Oxygen Plasma Treatment of Solution- Processed Indium Oxide Thin Film Transistors. [Display omitted] • The surface of indium oxide TFT was treated by focusing oxygen plasma. • Charge carrier mobility was optimized via the dopant concentration. • A large improvement in performance and stability was observed. In 2 O 3 is a transparent semiconductor layer due to its transparency, high mobility, and solution processability. In this paper, we study the effect of focused oxygen plasma treatment on solution processed indium oxide films annealed at 250 °C and analyze the effect of the gas flow rate. Thin film transistor devices were prepared based on pristine In 2 O 3 films and films treated with oxygen plasma using flow rates of 3, 6, and 9 sccm. The results show that controlling the plasma flow rate can be used to finetune the device characteristics, and the selecting the optimal flow rate is important to improve the electron mobility, threshold voltage, on/off current ratio, and the electrical stability of the devices. The In 2 O 3 TFTs treated at 6 sccm showed the best performance with mobility of 2.19 cm2V−1s−1, threshold voltage of of 4.25 V, and on/off current ratio of 2.13 × 106. The successful fabrication of high-performance, low-temperature solution deposited indium oxide transistors using the focused oxygen plasma treatment for electrical device applications demonstrates the practical potential of this treatment method for future transparent electronics. [ABSTRACT FROM AUTHOR]

A novel composite based on a polymer (P(VDF-TrFE)) and a two-dimensional material (graphene flower) was proposed as the active layer of an interdigitated electrode (IDEs) based humidity sensor. Silver (Ag) IDEs were screen printed on a flexible polyethylene terephthalate (PET) substrate followed by spin coating the active layer of P(VDF-TrFE)/graphene flower on its surface. It was observed that this sensor responds to a wide relative humidity range (RH%) of 8–98% with a fast response and recovery time of 0.8 s and 2.5 s for the capacitance, respectively. The fabricated sensor displayed an inversely proportional response between capacitance and RH%, while a directly proportional relationship was observed between its impedance and RH%. P(VDF-TrFE)/graphene flower-based flexible humidity sensor exhibited high sensitivity with an average change of capacitance as 0.0558 pF/RH%. Stability of obtained results was monitored for two weeks without any considerable change in the original values, signifying its high reliability. Various chemical, morphological, and electrical characterizations were performed to comprehensively study the humidity-sensing behavior of this advanced composite. The fabricated sensor was successfully used for the applications of health monitoring and measuring the water content in the environment.

Organic solar cells, processed from solution at various optimizing device parameters, were investigated. The device’s active-layer film-thicknesses were optimized while depositing at different spin speeds where 120-nm-thick layer (D2) gives maximum power conversion efficiency of 2.9%, annealed at 165 °C. The reason is ascribed as sufficient light absorption, excitons dissociation/diffusion and carriers transportation. In the case of Ca/Al, being as a top electrode rather than LiF/Al and Al, substantial efficiency enhancement, from 1.70% to 2.78%, was obtained at low temperature, 130 °C, providing ease for charge collection and pertaining conductive nature of increased resistivity at high temperature.

Flexible MoO3/silver nanowire (AgNW)/MoO3/TiO2/Epoxy electrodes with comparable performance to ITO were fabricated by a scalable solution-processed method with lamination assistance for transparent and conductive applications. Silver nanoparticle-based electrodes were also prepared for comparison. Using a simple spin-coating and lamination-assisted planarization method, a full solution-based approach allows preparation of AgNW-based composite electrodes at temperatures as low as 140 °C. The resulting flexible AgNW-based electrodes exhibit higher transmittance of 82% at 550 nm and lower sheet resistance about 12–15 Ω sq−1, in comparison with the values of 68% and 22–25 Ω sq−1 separately for AgNP based electrodes. Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) reveals that the multi-stacked metal-oxide layers embedded with the AgNWs possess lower surface roughness (

The use of solution-processed photovoltaics is a low cost, low material-consuming way to harvest abundant solar energy. Organic semiconductors based on perovskite or colloidal quantum dot photovoltaics have been well developed in recent years; however, stability is still an important issue for these photovoltaic devices. By combining solution processing, chemical treatment, and sintering technology, compact and efficient CdTe nanocrystal (NC) solar cells can be fabricated with high stability by optimizing the architecture of devices. Here, we review the progress on solution-processed CdTe NC-based photovoltaics. We focus particularly on NC materials and the design of devices that provide a good p–n junction quality, a graded bandgap for extending the spectrum response, and interface engineering to decrease carrier recombination. We summarize the progress in this field and give some insight into device processing, including element doping, new hole transport material application, and the design of new devices. [ABSTRACT FROM AUTHOR]

Abstract We have synthesised new materials comprised of 9,9′-bifluorenylidene and dithienodiketopyrrolopyrrole units. While 9,9′-bifluorenylidene has been primarily used in non-fullerene acceptors, when used in combination with the diketopyrrolopyrrole moiety it can form donor materials that can be used in conjunction with fullerene acceptors. The compounds differ in the substituents on the 9,9′-bifluorenylidene (protonated = 1A and dimethoxy = 1B) moiety. The structure of both the neat and blend films with PC 70 BM were found to be strongly dependent on the processing solvent used. In particular, Grazing Incidence Wide Angle X-ray Scattering measurements of films of 1A or 1B blended with PC 70 BM prepared from chloroform or chloroform with o -dichlorobenzene as an additive showed that the donor material had no particular ordering. However, when 1,8-diiodooctane was added to the processing solvent the 1A blends showed liquid crystalline ordering while 1B formed well-defined crystallites with three-dimensional ordering. The difference in film structure had a profound effect on the device properties. For 1A the optimised blend ratio with PC 70 BM was 1:4, but when 1,8-diiodooctane was used as the additive the best ratio of 1A to fullerene was 1:1. The films containing the well-defined crystallites of 1B all performed poorly, which was ascribed to a lack of a percolation pathway for hole extraction. The best performing device was comprised of a 1:1 blend of 1A and PC 70 BM, which had a power conversion efficiency of 2.6%. [ABSTRACT FROM AUTHOR]

Eu 3+ -doped CdMoO 4 luminescent ultra-thin films were fabricated by a facile aqueous solution method. The thin films were characterized by means of X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), and the results showed that Eu 3+ ions are doped into CdMoO 4 and the luminescent thin films are dense and smooth. Photoluminescence (PL) spectra, UV–vis absorption spectra and lifetimes were also used to characterize luminescent properties of the resulting films. The optimal doping concentration was found to be 10 mol% for the Eu 3+ -doped CdMoO 4 luminescent ultra-thin films. [ABSTRACT FROM AUTHOR]

Although impressive progress has been made in improving the performance of organic thin film transistors (OTFTs), the high operation voltage resulting from the low gate capacitance density of traditional SiO2 remains a severe limitation that hinders OTFTs'development in practical applications. In this regard, developing new materials with high-k characteristics at low cost is of great scientific and technological importance in the area of both academia and industry. Here, we introduce a simple solution-based technique to fabricate high-k metal oxide dielectric system (ATO) at low-temperature, which can be used effectively to realize low-voltage operation of OTFTs. On the other hand, it is well known that the properties of the dielectric/semiconductor and electrode/semiconductor interfaces are crucial in controlling the electrical properties of OTFTs. By optimizing the above two interfaces with octadecylphosphonic acid (ODPA) self-assembled monolayer (SAM) and properly modified low-cost Cu, obviously improved device performance is attained in our low-voltage OTFTs. Further more, organic electronic devices on flexible substrates have attracted much attention due to their low-cost, rollability, large-area processability, and so on. Basing on the above results, outstanding electrical performance is achieved in flexible devices. Our studies demonstrate an effective way to realize low-voltage, high-performance OTFTs at low-cost.

Solution-processed hybrid solar cells have been well developed in the last twenty years due to the advantages of low cost, low material-consuming and simple fabricating technology. However, the performance, stability and film quality of hybrid solar cells need to be further improved for future commercial application (with a lifetime up to 20 years and power conversion efficiency higher than 15%). By combining the merits of organic polymers and nanocrystals (NC), the reasonable design of interface engineering and device architecture, the performance coupled with stability of hybrid solar cells can be significantly improved. This review gives a brief conclusive introduction to the progress on solution-processed organic/inorganic semiconductor hybrid solar cells, including a summary of the development of hybrid solar cells in recent years, the strategy of hybrid solar cells with different structures and the incorporation of new organic hole transport materials with new insight into device processing for high efficiency. This paper also puts forward some suggestions and guidance for the future development of high-performance NC-based photovoltaics.

We report the effect of bias stress on the drain current and threshold voltage of n-channel thin-film transistors based on solution processed In _2 O _3 layers. Application of a positive gate bias for variable time-periods led to displacements of the transfer curves in the positive gate bias direction. On switching off the gate bias, the transfer curves returned close to their pre-stress state on a timescale similar to that when the gate bias was switched on. The time dependence of the threshold voltage shift is described well by a stretched-exponential model. The temporal behaviour of the threshold voltage shifts is consistent with charge trapping as the dominant effect, although some defect formation cannot be ruled out.

A series of Eu ^3+ and Tb ^3+ co-doped CaMoO _4 /SrMoO _4 luminescent thin films were prepared by a facile solution method, and they were annealed at 550 °C for 2 h. The luminescent properties of the thin films were studied, which involve the energy transfer from Tb ^3+ to Eu ^3+ . The emission color can be changed from green to red, with increasing Eu ^3+ doping concentration in Tb ^3+ -doped CaMoO _4 /SrMoO _4 thin films. In addition, it was observed that the PL intensity of Eu ^3+ will enhance when Tb ^3+ ions are incorporated into Eu ^3+ -doped CaMoO _4 /SrMoO _4 thin films. The optical band gaps of the luminescent thin films are found to be in the range of 4.49 to 4.72 eV. These results revealed that Eu ^3+ and Tb ^3+ co-doped CaMoO _4 /SrMoO _4 luminescent thin films have a significantly potential application in electroluminescent devices.