Search

Perovskite light-emitting diodes (PeLEDs) have been attracting widespread attention owing to their unique advantages such as high luminance, narrow emission spectra and high color purity. However, the solution-processed fabrication method makes the deposition of multi-emitting layers of perovskite films for white PeLEDs challenging. Moreover, modulating the emission color by adjusting the thickness of the emitting layers will result in reduced optoelectronic performance of the polycrystalline perovskite films. Therefore, strategies for achieving high-performance white PeLEDs are urgently needed. This study developed a newly designed perovskite/organic hybrid tandem light-emitting diode (POTLED) by combining a bottom PeLED unit with a top organic light-emitting diode (OLED) unit. The vacuum deposition process of the OLED avoids damaging the underlying PeLED unit. Additionally, the emission color of the tandem device can be tuned by adjusting the thickness of the organic emitting layer while maintaining the optoelectronic properties of the perovskite layer. As a result, a high-efficiency green POTLED with an outstanding current efficiency of 144.2 cd A−1, an external quantum efficiency of 41.1%, and a luminance of over 32 000 cd m−2 is achieved, illustrating the feasibility and potential of the hybrid tandem perovskite-organic structure to realize high-efficiency white-color perovskite-based devices. [ABSTRACT FROM AUTHOR]

Mixed-organic-cation FA1−xMAxPbI3 perovskites are currently attracting intensive attention for their high photovoltaic performance. However, FA1−xMAxPbI3 usually has an undesired non-perovskite phase leading to a compromised efficiency, and a facile strategy to achieve pure-phase FA1−xMAxPbI3 has been rarely reported. Here, we demonstrate a facile approach to form δ-phase free FA1−xMAxPbI3 using a non-stoichiometric precursor solution. It is found that a small amount of excess methylammonium iodide (MAI) added to the precursor solution has a profound effect on perovskite crystallization during the liquid-to-solid phase transformation. Using an in situ photoluminescence spectroscopy measurement, it is found that the excess MAI can promote the formation of FA1−xMAxPbI3 and facilitate the cation-exchange between organic FA+ and MA+ during the film formation. Based on the optimized pure-phase FA1−xMAxPbI3, the perovskite solar cells exhibit an encouraging power conversion efficiency (PCE) of 17.40%. This study demonstrates a facile method to achieve high performance FA dominating mixed-organic-cation perovskite devices while providing insight into the ion-exchange process during perovskite crystallization. [ABSTRACT FROM AUTHOR]

Developing facile strategies that enable high-performance perovskite solar cell (PSC) fabrication in ambient air is appealing yet challenging for low-cost and large-scale industrial deployment. However, attempts in this regard are still limited to methylammonium lead triiodide (CH3NH3PbI3), which lags significantly behind the rapid development of the state-of-the-art formamidinium (FA) based mixed perovskites. Here, a PbI2–(CsI)0.15–(FAI)x intermediate complex is proposed to unlock the processing limitation and efficiently facilitate the growth of high-quality mixed-cation Cs0.15FA0.85PbI3 perovskite films in ambient air with relative humidity (RH) as high as 70 ± 10%. It is found that the PbI2–(CsI)0.15–(FAI)x (x = 0.2 to 0.4) intermediate complex consisting of a mixture of composites is favorable for the conversion of PbI2 to high-quality Cs0.15FA0.85PbI3 perovskite. Eventually, it reduces the required FAI concentration deposited on the intermediate for the conversion of PbI2 to perovskite, which allows the strong hygroscopic FAI to be processed in ambient air. With the PbI2–(CsI)0.15–(FAI)0.3 intermediate complex, a low-temperature air-processed planar Cs0.15FA0.85PbI3 PSC achieves a champion power conversion efficiency (PCE) of 15.56% with superior thermal-stability and photo-durability, demonstrating its great potential for the large scale development of PSCs. [ABSTRACT FROM AUTHOR]

Green phosphorescent inverted organic light-emitting diodes (IOLEDs) with 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN)/aluminium/n-doped 4,7-diphenyl-1,10-phenanthroline (Bphen) used as an electron injection layer (EIL) were demonstrated. The IOLED shows the lowest driving voltage of 4.5 V at 10 000 cd m−2 to date. The electron injection effects of different interlayers were further investigated by ultraviolet photoelectron spectroscopy (UPS) and evaluating the electron injection efficiency. For application in large-sized OLEDs, a 120 × 120 mm2 flexible IOLED was successfully fabricated based on this inverted structure. [ABSTRACT FROM AUTHOR]

The authors develop an aqueous solution-processed hole injection layer, MoO3 doped copper phthalocyanine-3,4′,4′′,4′′′-tetra-sulfonated acid tetra sodium salt (TS-CuPc), in organic light-emitting diodes (OLEDs) via an environmentally-friendly and easy fabrication process. The generation of a charge transfer complex in TS-CuPc:MoO3 composite films is confirmed by absorption spectra and X-ray photoemission spectroscopy (XPS) measurements. Enhanced hole injection in OLEDs is attributed to the decreased hole barrier at the ITO side, which is in agreement with the Schottky thermal emission evaluation. The efficient modification of ITO by TS-CuPc:MoO3 is further confirmed by ultraviolet photoemission spectroscopy (UPS) measurements. [ABSTRACT FROM AUTHOR]

A new host material BCz–Si for blue and white phosphorescent organic light-emitting devices was designed and synthesized. The introduction of the triphenylsilyl moiety into the BCz unit can efficiently tune the HOMO/LUMO energy levels and maintain high triplet energy. Its carrier mobility, thermal, photophysical, and electrochemical properties were also systematically investigated. The high triplet energy of BCz–Si ensures efficient energy transfer from the host to the triplet emitter FIrpic. The blue device using BCz–Si as a host material achieved a maximum quantum efficiency of 21.0%, corresponding to a current efficiency and power efficiency as high as 46.5 cd A−1 and 45.8 lm W−1, respectively; meanwhile, high efficiency white phosphorescent OLEDs hosted by BCz–Si were also fabricated with a maximum external quantum efficiency of 24.6%, 70.5 cd A−1 for two-color based and 21.5%, 50.1 cd A−1 for three color based devices. [ABSTRACT FROM AUTHOR]

Capping layers (CPLs) are commonly employed in top-emitting organic light-emitting diodes (TEOLEDs) due to their ability to optimize color purity, enhance external light out-coupling efficiency, and improve device stability. However, the mismatch in refractive index between CPLs and thin film encapsulation (TFE) often induces light trapping. This study introduces a novel approach by combining a low refractive index material, lithium fluoride (LiF), with the traditional TFE material, silicon nitride (SiN x ), to form a combined CPL (LiF/SiN x ), resulting in improved light outcoupling and light reflection properties. The significant refractive index contrast between LiF and SiN x can facilitate enhanced light extraction by redirecting internally reflected light through evanescent waves. Moreover, the LiF/SiN x CPLs function as a secondary resonant cavity, leading to reduced emission spectral bandwidth and enhanced light extraction compared to the control TEOLEDs that only incorporate the primary cavity of organic active layers. As a result, incorporating the LiF/SiN x CPLs significantly increases current efficiency from 125.0 cd A -1 to 163.6 cd A -1 for green devices, from 71.2 cd A -1 to 110.1 cd A -1 for red devices, and from 43.1 cd A -1 to 53.1 cd A -1 for blue devices, with the corresponding full width at half maximum decreased from 20 nm to 10 nm, 26 nm to 14 nm, and 21 nm to 12 nm, respectively, demonstrating the compatibility of the CPLs with different color devices. Notably, an LT 95 lifetime of 51 300 hours for green devices was achieved when tested at 1000 cd m -2 . Utilizing narrow-band light emission without spectral overlap of each color enables the generation of purer and more vivid colors for display.

Perovskite-based tandem solar cells (PTSCs) have made remarkable achievements in recent years, and the highest certified power conversion efficiency (PCE) of 33.9% has been achieved in perovskite/silicon tandem solar cells (PSTSCs), indicating their great commercialization potential. Nevertheless, the performance of PTSCs continues to be hindered by the compromised performance of wide-bandgap perovskite solar cells (WPSCs), particularly the high V OC deficit of WPSCs. Therefore, numerous strategies have been developed to minimize the V OC loss of WPSCs. Herein, we sort to comprehensively review about the reported studies on reducing the V OC deficit of WPSCs, focusing on interface modification, charge transport material (CTM) exploration, and additive engineering, with the aim of providing guidelines for increasing the V OC of WPSCs. Finally, we will provide a conclusive outlook on WPSCs, sharing our perspectives to inspire further advancements in both WPSCs and PTSCs.