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All‐inorganic CsPbI2Br perovskite has attracted great attention due to the stable crystal structure and moisture resistance, and its 1.91 eV bandgap is close to the optimal bandgap of indoor artificial light sources, making it be the best candidate for the indoor photovoltaics (IPVs) to power a wide range of internet of things related electronic devices. Herein, we report on the preparation of CsPbI2Br with α‐phase and the improvement of its phase stability by adding lead acetate in the CsPbI2Br precursor. A series of dopant‐free conjugated polymers (P3HT, PBDB‐T, and PM6) with different highest occupied molecular orbital energy levels are introduced as hole transport layers for building IPV devices. The PM6 based devices having better energy alignment with perovskite demonstrate best indoor photovoltaic performance, giving a remarkable open‐circuit voltage of 1.15 V and high fill factor of 81.86% under 1000 lux (330 µW cm−2) light‐emitting diode illumination, and finally realizing a decent power conversion efficiency of 33.68%. Our findings suggest that collaboratively optimize the CsPbI2Br layer and hole transport layer is an effective approach to realize high performance IPVs. [ABSTRACT FROM AUTHOR]

Quasi‐two‐dimensional (quasi‐2D) perovskites are attracting much attention due to their impressive luminescence properties. However, the introduction of insulating bulky cations reduces the charge transport property of mixed‐dimensional perovskites and leads to lowered brightness and increased turn‐on voltage. The trade‐off between high photoluminescence quantum yield (PLQY) and electrical conductivity should be well manipulated to obtain high‐performance perovskite light‐emitting diodes (PeLEDs). Herein, quasi‐2D perovskite BA2(CsPbBr3)n‐1PbBr4‐PEO with high PLQY and excellent carrier injection efficiency is demonstrated by incorporating bulky n‐butylammonium bromide (BABr), CsPbBr3, and polyethylene oxide (PEO). BA can intercalate into the three‐dimensional perovskite framework to form a layered (quasi‐2D) perovskite structure. The ion conductive polymer PEO is used to protect quasi‐2D perovskite crystals. Additional BABr is removed by using anhydrous isopropyl alcohol as a washing agent due to its selective dissolubility. By carefully modulating the optical and electrical properties of quasi‐2D perovskite films, the maximum luminance of PeLEDs is dramatically enhanced from 191 to 33533 cd m−2, which is the brightest green quasi‐2D PeLED reported thus far, leading to an increase in external quantum efficiency from 1.81% to 8.42%. This work provides a promising route to control the optical and electrical properties of quasi‐2D perovskite films for high‐performance optoelectronic devices. A quasi‐2D perovskite with high photoluminescence quantum yield and excellent carrier injection efficiency is demonstrated by incorporating n‐butylammonium bromide, CsPbBr3 and polyethylene oxide. By modulating the optical and electrical properties of quasi‐2D perovskite films, the maximum luminance of PeLEDs is dramatically enhanced from 191 to 33 533 cd m−2, which is the brightest value yet observed for green quasi‐2D PeLEDs. [ABSTRACT FROM AUTHOR]

Abstract: For highly luminescent solid-state applications, the twisted or spiro-configured conjugated molecules are mostly considered as the proper choices because the coplanar ones usually have intensively intermolecular π–π interactions, which lead to fluorescence quenching and red-shift. In this study, the two prepared parallel H-shaped phenylenevinylenes with coplanar configuration show the special case. Due to their characteristics of multi-branches, these coplanar multi-branched molecules prefer to form stable amorphous morphology in thin films were verified by the XRDs and AFM. The amorphous thin films show very weak intermolecular actions, with intrinsic differences on both steady and transient optical properties from the crystalline states. The non-doped electroluminescent devices based on them show highly luminescent blue emissions. Both their luminance (20490cdm−2) and efficiency (2.8cdA−1/2.6lmW−1) are comparable with the performances of the cross dimeric OPVs which have similar constructing blocks to the H-shaped molecules and with the same EL device configurations. [Copyright &y& Elsevier]

Abstract: We reported an asymmetric phenylenevinylene with a cis double bond 2-(4-(p-tolyl)styryl)-1,4-dip-tolylbenzene (cis-TSDTB) and its use as efficient deep-blue emitter for organic light-emitting diodes (OLEDs) applications. The crystal structure of cis-TSDTB showed torsion configuration and asymmetric geometry, which make it packing in a reduced intermolecular interaction arrangement. And its single crystals showed excellent fluorescence owing to this unique molecular configuration. Typical OLEDs using cis-TSDTB as non-doped emitters exhibited saturated blue light with the CIE 1931 coordinates of (0.15,0.10), which is quite close to the National Television Standards Committee (NTSC) blue standard. High luminescence efficiency (3.4cdA−1) and high brightness (9855cdm−2) have been realized in the device. All of these outstanding results indicated that cis-phenylenevinylene will be a promising candidate as blue light-emitting materials. [Copyright &y& Elsevier]

Abstract: A series of hole-transporting molecules based on spiro(fluorene-9,9′-xanthene) were designed and synthesized by a copper-catalyzed modified Ullmann reaction. These compounds have very high-lying HOMO levels (∼5.0eV), which are beneficial for the hole-injection from ITO anode. The double-layer EL devices using DPA-SFXMe and DPA-SFXBu as hole-transporting layers exhibit lower turn-on voltage and higher efficiency compared with those of a typical NPB-based device. The DPA-SFXBu-based device exhibits high maximum luminescence of 21,712cd/m2, and its power efficiency can reach a value of 2.31lm/W, which is nearly 90% higher than that of a similar NPB-based device. [Copyright &y& Elsevier]

Abstract: The synthesis and luminescence of four new iridium (III) diazine complexes (1–4) were investigated. HOMO and LUMO energy levels of the complexes were estimated according to the electrochemical performance and the UV–Vis absorption spectra, showing the pyrimidine complexes have a larger increase for the LUMO than the HOMO orbital in comparison with the pyrazine complexes. Several high-efficiency yellow and green OLEDs based on phosphorescent iridium (III) diazine complexes were obtained. The devices emitting yellow light based on 1 with turn-on voltage of 4.1V exhibited an external quantum efficiency of 13.2% (power efficiency 20.3lm/W), a maximum current efficiency of 37.3cd/A. The electroluminescent performance for the green iridium pyrimidine complex of 3 is comparable to that of the iridium pyridine complex (PPY)2Ir(acac) (PPY=2-phenylpyridine), which is among the best reported. [Copyright &y& Elsevier]

Abstract: Polymer-based blue electrophosphorescent light-emitting diodes are reported by doping iridium(III) diazine complex (DFPPM)2Ir(pic) (DFPPM=2-(2,4-difluorophenyl)-pyrimidine, pic=picolinate) in poly(vinylcarbazole) (PVK) as the source of emission. The iridium(III) diazine complex shows sky blue emission with its maximum emission peak at 476nm originating from an admixture of triplet metal-to-ligand charge-transfer and ligand-centered states. The (DFPPM)2Ir(pic)-doped device furnishes a maximum external quantum efficiency of 2.2% and power efficiency of 1.9lm/W at a 10wt% doping concentration. [Copyright &y& Elsevier]

Abstract: A series of novel mesogen-jacketed polymers, poly{2,5-bis[(5-tert-butylphenyl)-1,3,4-oxadiazole]styrene} (P-Ct) and poly{2,5-bis[(5-alkoxyl-phenyl)-1,3,4-oxadiazole]styrene} (P-OCn, n is the number of carbons in the alkoxyl groups, n =6, 8, 10, 12, 14), were incorporated into polymer light-emitting device as the light-emitting layers. All of the polymers had excellent solubility in common organic solvents. The UV and PL spectra for P-Ct were 312 and 400nm while for P-OCn they were around 328 and 420nm in the film. There was no red shift in the PL spectrum of P-Ct after heat treatment which maybe related to the jacketed structure. All of the polymers showed high PL quantum yields in THF solution. From the cyclic voltammetry measurement at room temperature, HOMO levels of the polymers were varied from −5.66 to −6.12eV, LUMO levels were varied from −2.45 to −2.81eV. Furthermore, the influence of the alkoxyl lengths in four different device configurations was compared. For the device configuration c: ITO/PVK/P-OC8/Ca/Ag, the maximum luminance and maximum external quantum efficiency were obtained for P-OC8 which maybe related to the easier electron injection and transport. Efficiency of P-OC8 was not improved with device d which proved the electron transporting characteristics of P-OC8. [Copyright &y& Elsevier]