Showing papers by "Abd. Rashid bin Mohd Yusoff published in 2022"

Perovskite light-emitting diodes

Abstract: Light-emitting diodes based on halide perovskites have undergone rapid development in recent years and can now offer external quantum efficiencies of over 23%. However, the practical application of such devices is still limited by a number of factors, including the poor efficiency of blue-emitting devices, difficulty in accessing emission wavelengths above 800 nm, a decrease in external quantum efficiency at high current density, a lack of understanding of the effect of the electric field on mobile ions present in the perovskite materials, and short device lifetimes. Here we review the development of perovskite light-emitting diodes. We examine the key challenges involved in creating efficient and stable devices, and consider methods to alleviate the poor efficiency of blue-emitting devices, leverage emission in the long infrared region and create spin-polarized light-emitting diodes. This Review examines the development of perovskite light-emitting diodes, exploring the key challenges involved in creating efficient and stable devices.

Toward color-selective printed organic photodetectors for high-resolution image sensors: From fundamentals to potential commercialization

Abstract: The technology to record image information at high resolution is of great importance in the optical areas of applied physics and biochemical imaging, as well as in commercial imaging applications such as cameras and machine vision. Organic semiconductors are drawing interest as photodetecting materials for next-generation high-resolution image sensors (IS) owing to their excellent properties such as high absorption coefficient, and color tunability and cost-effective manufacturability. These advantages offer the potential to exceed the technical limitation of silicon-based IS. This article reviews the state-of-the-art technologies of materials and devices in solution-processed organic photodiodes (OPDs) to meet the demands for future high-resolution ISs, which involves challenges ranging from the absence of a fundamental understanding of OPDs to commercialization requirements. Further, this article overviews the progress in the industry as well as academic society. The various requirements and technologies for the development of color-filter-free OPDs with narrow-wavelength detection are also discussed. This review concludes with an outlook of advances in these materials and devices to open up new commercialization routes.

Charge Transport Materials for Mesoscopic Perovskite Solar Cells

Abstract: Organic–inorganic perovskite solar cells have achieved an impressive power conversion efficiency of up to 25.6% and 24.8%, respectively, for single and multijunction tandem architectures due to the huge progress made...

Defect passivation in perovskite solar cells using an amino-functionalized BODIPY fluorophore

Abstract: The presence of defects formed during the growth and crystallization of perovskite films is a limiting factor to achieve high efficiency and stability in perovskite solar cells.

Sn‐Based Perovskite Halides for Electronic Devices

Abstract: Because of its less toxicity and electronic structure analogous to that of lead, tin halide perovskite (THP) is currently one of the most favorable candidates as an active layer for optoelectronic and electric devices such as solar cells, photodiodes, and field‐effect transistors (FETs). Promising photovoltaics and FETs performances have been recently demonstrated because of their desirable electrical and optical properties. Nevertheless, THP's easy oxidation from Sn2+ to Sn4+, easy formation of tin vacancy, uncontrollable film morphology and crystallinity, and interface instability severely impede its widespread application. This review paper aims to provide a basic understanding of THP as a semiconductor by highlighting the physical structure, energy band structure, electrical properties, and doping mechanisms. Additionally, the key chemical instability issues of THPs are discussed, which are identified as the potential bottleneck for further device development. Based on the understanding of the THPs properties, the key recent progress of THP‐based solar cells and FETs is briefly discussed. To conclude, current challenges and perspective opportunities are highlighted.

Functionalized BODIPYs as Tailor‐Made and Universal Interlayers for Efficient and Stable Organic and Perovskite Solar Cells

Abstract: Solar cells based on metal halide perovskite and polymer donor:nonfullerene acceptor blend absorbers have recently witnessed a significant rise in their photovoltaic performance. However, they still suffer from some instability issues originating from the inferior interface quality and poor nanomorphology of the absorber layer. In this work, a series of functionalized boron‐dipyrromethene, BODIPY, molecules are introduced as ultrathin interlayers at the absorber/electron transport layer interface. This study indicates that BODIPY compounds with a high molecular dipole moment can enhance the device performance mainly due to better interface energy level alignment. They also induce passivation of defect traps and improvement in the charge transport properties of the absorber layer coated on top of them. Among the various compounds used, amino‐functionalized BODIPY, owing to the synergetic effect of the abovementioned factors, enables the highest power conversion efficiency in organic (15.69%) as well as in perovskite solar cells (20.12%). Amino‐functionalized BODIPY also demonstrates an enhanced stability under continuous illumination (in nitrogen) without and with heating (at 65 °C) for 1000 h. These results pave the way for the implementation of molecules with tailor‐made functionalities in high efficiency and stable solution‐based photovoltaic devices of the future.

Photonic nanostructures mimicking floral epidermis for perovskite solar cells

Abstract: Here, we report photonic nanostructures replicated from the adaxial epidermis of flower petals onto light-polymerized coatings using low-cost nanoimprint lithography at ambient temperature. These multifunctional nanocoatings are applied to confer enhanced light trapping, water repellence, and UV light and environmental moisture protection features in perovskite solar cells. The former feature helps attain a maximum power conversion efficiency of 24.61% (21.01% for the reference cell) without any additional device optimization. Added to these merits, the nanocoatings also enable stable operation under AM 1.5G and UV light continuous illumination or in real-world conditions. Our engineering approach provides a simple way to produce multifunctional nanocoatings optimized by nature's wisdom.

Reduced defect density in crystalline halide perovskite films via methylamine treatment for the application in photodetectors

Abstract: Considerable efforts have been devoted to optimizing and controlling the morphology and electronic properties of lead halide perovskites. The defect density of a perovskite layer strongly depends on the processing conditions. Consequently, the fabrication process of high-quality films is often complex, and reproducibility is a challenge. In this work, we present a methylamine gas-based method to recrystallize perovskite layers of any given quality in a controlled way, leading to millimeter-sized domains. Crystallinity significantly increases upon methylamine treatment, and crystal growth follows a preferred orientation. Photoluminescence- and space-charge limited current measurements show that the trap density halves after recrystallization. Conductive atomic force microscopy measurements show a higher surface conductivity and an improved spatial homogeneity after methylamine treatment. When applied in photodetectors, the improved film quality of the recrystallized films leads to increased detectivities of ≈4 × 1011 Jones compared to 3 × 109 Jones of a reference device. The response time falls from 0.1 to 10−5 s upon methylamine treatment. Our work, thus, presents a promising route to fabricating reproducible, high-quality perovskite films through well-controllable recrystallization.

Core–shell carbon-polymer quantum dot passivation for near infrared perovskite light emitting diodes

Abstract: High-performance perovskite light-emitting diodes (PeLEDs) require a high quality perovskite emitter and appropriate charge transport layers to facilitate charge injection and transport within the device. Solution-processed n-type metal oxides represent a judicious choice for the electron transport layer (ETL); however, they do not always present surface properties and energetics compatible with the perovskite emitter. Moreover, the emitter itself exhibits poor nanomorphology and defect traps that compromise the device performance. Here, we modulate the surface properties and interface energetics between the tin oxide (SnO2) ETL with the perovskite emitter by using an amino functionalized difluoro{2-[1-(3,5-dimethyl-2H-pyrrol-2-ylidene-N)ethyl]-3,5-dimethyl-1H-pyrrolato-N}boron compound and passivate the defects present in the perovskite matrix with carbon-polymer core–shell quantum dots inserted into the perovskite precursor. Both these approaches synergistically improve the perovskite layer nanomorphology and enhance the radiative recombination. These properties resulted in the fabrication of near-infrared PeLEDs based on formamidinium lead iodide (FAPbI3) with a high radiance of 92 W sr−1 m−2, an external quantum efficiency (EQE) of 14%, reduced efficiency roll-off and prolonged lifetime. In particular, the modified device retained 80% of the initial EQE (T80) for 33 h compared to 6 h of the reference cell.

Carbon Nanodots as Electron Transport Materials in Organic Light Emitting Diodes and Solar Cells

Abstract: Charge injection and transport interlayers play a crucial role in many classes of optoelectronics, including organic and perovskite ones. Here, we demonstrate the beneficial role of carbon nanodots, both pristine and nitrogen-functionalized, as electron transport materials in organic light emitting diodes (OLEDs) and organic solar cells (OSCs). Pristine (referred to as C-dots) and nitrogen-functionalized (referred to as NC-dots) carbon dots are systematically studied regarding their properties by using cyclic voltammetry, Fourier-transform infrared (FTIR) and UV–Vis absorption spectroscopy in order to reveal their energetic alignment and possible interaction with the organic semiconductor’s emissive layer. Atomic force microscopy unravels the ultra-thin nature of the interlayers. They are next applied as interlayers between an Al metal cathode and a conventional green-yellow copolymer—in particular, (poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1′,3}-thiadiazole)], F8BT)—used as an emissive layer in fluorescent OLEDs. Electrical measurements indicate that both the C-dot- and NC-dot-based OLED devices present significant improvements in their current and luminescent characteristics, mainly due to a decrease in electron injection barrier. Both C-dots and NC-dots are also used as cathode interfacial layers in OSCs with an inverted architecture. An increase of nearly 10% in power conversion efficiency (PCE) for the devices using the C-dots and NC-dots compared to the reference one is achieved. The application of low-cost solution-processed materials in OLEDs and OSCs may contribute to their wide implementation in large-area applications.

A Disposable and Noncontact Paper Breathalyzer Based on Small Conjugated Molecules/Carbon Nanotubes Electrodes

Abstract: Herein, N,N′‐di(decyl)‐3,4,9,10‐perylenebis(dicarboximide) (PDIC10) is first functionalized by hydrothermal synthesis method and processed onto single‐walled carbon nanotube (SWCN) electrodes and paper substrate. The PDC10/SWCN/paper device can be applied as a noncontact breathalyzer to detect and quantify ethanol alcohol and determine equivalent blood alcohol concentration (BAC). The sensing mechanism increases the electrical resistance upon ethanol alcohol (EtOH) exposition. This device allows the quantification of BAC values from 0.01% to 0.2%, with ΔR (%) of 2–25% in this range, with adequate stability operating in cycles.

13‐5: Quantum‐Dot‐in‐Perovskite Near‐Infrared Light‐Emitting Diodes

Abstract: Quantum dots represent a unique class of solution-processed semiconductors with unprecedented optoelectronic properties such as charge transport capability and light absorption/emission. Regarding the latter, the electroluminescence of these nanocrystals can spun a wide wavelength range from the visible to the near infrared through size engineering. However, they exhibit low photoluminescence quantum yield and inferior charge transport properties which hinders their application to light-emitting diodes. On the other hand, halide perovskite semiconductors exhibit high charge carrier mobility and photoluminescence quantum efficiency approaching unity. However, their emission maxima cannot spun the whole near infrared range due to bandgap induced limitations. Here, we report unique combinations of these classes of semiconductors that allowed the fabrication of efficient near infrared electroluminescent hybrid quantum dot-in-perovskite device. In the first approach, core-shell carbon polymer quantum dots were embedded into the perovskite emissive layer to induce passivation of defect sites and modify the nanomorphology hence resulting to significant efficiency enhancement. In the second approach, silica-encapsulated silver sulphide quantum dots served as the emissive nanocrystals that were dispersed in a caesium-containing triple cation perovskite matrix. The latter acted as a highly conductive medium that also offers effective passivation to the emissive nanocrystals. As a result, high external quantum efficiency for a long near infrared wavelength peak electroluminescence was achieved.