For the hole transport material (HTM) of methylammonium lead(II) triiodide (MAPbI3)-inverted perovskite solar cells (PVSCs), we have demonstrated that a dual layer of NiO x , a nanoporous NiO x (np-NiO x ) on a compact NiO x (cp-NiO x ), outperforms a single layer of cp-NiO x . With a dual layer of cp/np-NiO x HTM, we have achieved a PCE as high as 20.7%, which is one of the highest PCEs among inverted PVSCs using NiO x as HTM without doping NiO x or an interlayer between NiO x and the perovskite. In this report, scanning electron microscopy (SEM), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy have demonstrated that the interfacial contact of MAPbI3 is better with np-NiO x than with cp-NiO x . Direct current conductivity measurements showed a higher conductivity of cp/np-NiO x compared to cp-NiO x . A deeper HOMO energy level was found for cp/np-NiO x compared to cp-NiO x . The space-charge limited current (SCLC) method estimated a higher trap-state density in cp-NiO x than in cp/np-NiO x . The studies of light intensity-dependent open-circuit voltage (V OC) and short-circuit current density (J SC) revealed a less charge recombination in cp/np-NiO x than in cp-NiO x PVSCs. We have also found and verified that using a larger volume of the ethylenediamine stabilizer in the preparation of np-NiO x results in a higher-performance cp/np-NiO x HTM.

The recent past has witnessed remarkable progress in organic electronics, driven by the quest for flexible, lightweight, and cost-effective electronic devices. Semiconducting polymers (SCPs) have emerged as key materials in this field, offering unique electronic and optoelectronic properties along with mechanical flexibility. This study focuses on designing, synthesizing, and utilizing novel donor-acceptor (D-A) copolymer-based SCPs introducing a difluorothiophene moiety in the polymeric backbone. The importance of fluorine substitution for backbone planarity was verified by density functional theory calculations, comparing it with a nonfluorine substituted counterpart. Through the Unidirectional Floating Film Transfer Method (UFTM), we fabricated highly oriented thin films, resulting in increased optical anisotropy with dichroic ratios reaching 19.3 in PC20-FT thin films, one of the highest optical anisotropy observed for solution processable SCP thin films. X-ray diffraction and atomic force microscopy results validated the increase in the crystallinity and domain size with the increasing alkyl chain length. Finally, we elucidate these findings in the context of electrical applications by fabricating organic field-effect transistors revealing anisotropic charge transport achieving a promising mobility of 1.24 cm2V-1s-1 and mobility anisotropy of 39.5. This study offers insights into the design principles and performance optimization of SCP-based devices, paving the way for advancements in plastic electronics.

The stability of MAPbI 3 ‐based (MA stands for methylammonium) perovskite solar cells (PVSCs) has been carefully examined by ZnO@CdS nanoparticle‐embedded epoxy films (EP‐ZC films), device encapsulation (of glass sheet and UV‐curing gel), and in different temperatures, 10 °C, room temperature (no temperature control), and 65 °C. EP‐ZC films are used for shielding the short wavelength of the sunlight (UV, near UV, violet, and deep blue) which causes the photodegradation of MAPbI 3 and hence the decline of power conversion efficiency (PCE) of PVSCs. Some external quantum efficiency spectra of the device are recorded alongside of the 500 h continuous light‐soaking measurement of current density ( J )−voltage ( V ) of the devices. The time‐of‐flight secondary‐ion mass spectroscopy analysis is performed for a quantitative comparison of the iodide derived from the degradation of MAPbI 3 in the encapsulated devices with or without the light‐shielding EP‐ZC films at 10 °C and 65 °C, respectively. The EP‐ZC6 film shows the best protection for encapsulated PVSCs with 98% of the initial PCE at 10 °C after 500 h continuous light soaking. Herein, from the continuous light‐soaking results, one can prioritize the moisture, temperature, and light in the influence of the stability of PVSCs.

In this work, difluoro and dicyano substituted terpolymers, P6TI-3N1F, P6TI-1N1F, and P6TI-1N3F, based on isoindigo -sexithiophene & pi;-conjugated polymers have been designed and characterized. Together with two only cyano and only fluoro substituted copolymers, P6TIN and P6TIF, we have demonstrated that P6TI-1N1F is the champion terpolymer in terms of the ratio of electron/hole mobility, nanofibril and its agglomeration, mono -molecular and bimolecular charge recombination, polymer chain face-on alignment, and photoluminescence quenching in a binary thin film of polymer:PC71BM or polymer:IT4F. In the binary polymer solar cells (PSCs) based on a bullk heterojunction (BHJ) of either polymer:PC71BM or polymer:IT4F, P6TI-1N1F exhibits the highest fill factor of 67.62 % or 76.86 %, and hence the highest power conversion efficiency (PCE) of 10.4 % or 11.9 %. Corresponding ternary PSCs with a 100 nm thick BHJ of P6TI-1N1F:IT4F:PC71BM or P6TI-1N1F:Y6: PC71BM exhibit PCE as high as 12.8 % or 14.5 %. It is rarely seen in literature that the PCE of the ternary PSCs shows only minor decline to 12.4 % or 14.0 % when the thickness of BHJ increases from 100 nm to 300 nm.

This review article surveys the organic small molecular materials, light-emitting for most of them, being studied for the molecular alignment or orientation in thin films. Following a chronicle order, three practical characterization techniques, variable angle spectroscopic ellipsometry (VASE), angle-dependent photoluminescence (ADPL), and grazing incidence wide-angle x-ray scattering (GIWAXS) have been used to probe phosphorescence, thermally activated delayed fluorescence (TADF) materials, as well as those of non-phosphorescence and non-TADF materials.

Based on the classic 1,1′:4′,1″‐terphenyl fluorophore, a novel near‐ultraviolet (NUV) fluorescent BB4Ph (4,4″′‐bis(2,3,4,5‐tetraphenylphen‐1‐yl)(1,1′:4′,1″‐terphenyl) is designed, synthesized, and characterized. BB4Ph exhibits a NUV fluorescence with a λ max of 373 and 380 nm in solution and as a thin film, respectively. The grazing incidence wide‐angle X‐ray scattering (GIWAXS) reveals BB4Ph having a high value of order parameter ( S GIWAXS ) of 0.59 for a molecular layer array normal to the substrate; the angle‐dependent photoluminescence (ADPL) measurement shows Θ (horizontal–dipole ratios) as high as 95% with the neat film. The non‐doped BB4Ph organic light‐emitting diodes (OLEDs) show external quantum efficiency (EQE) up to 5.24% with 1931 Commission Internationale de l’ Eclairage coordinates (CIE x,y ) of (0.16, 0.04), a NUV electroluminescence. With 4P‐Cz (9,9′‐(1,1′:4′,1″:4″,1′″‐quaterphenyl‐4,4′″‐diyl)dicarbazole) as a dopant emitter, doped BB4Ph OLEDs show the highest EQE of 6.99% and a NUV 1931 CIE x,y (0.16, 0.04). The photoluminescence quantum yield is measured for the thin film of BB4Ph and 4P‐Cz:BB4Ph as 68% and 96%, respectively. Hence, the low limits of light outcoupling efficiency (η out ) of the two individual OLEDs are estimated as 31% and 29%, respectively.

Five mixing molar ratios, 1:0.6, 1:0.8, 1:1.0, 1:1.2, and 1:1.4, of conventional nickel(II) bis(acetylacetonate) (Ni(acac)(2)) and a diethanolamine (DEA) stabilizer have been tried for preparing precursor solutions in a sol-gel process for preparing the nickel(II/III) oxide (NiOx) hole-transporting material (HTM) in inverted methylammonium lead(II) triiodide (MAPbI(3))-based perovskite solar cells (PVSCs). Considering both the electronic property and the homogeneity of NiOx thin films, a 1:0.8 molar ratio of Na(acac)(2) and DEA in precursor solutions has been found to be optimal for the power conversion efficiency (PCE) up to 19.54% without any dopant in NiOx or the interlayer between NiOx and MAPbI(3). Three cyano group-containing photovoltaic polymers, benzodithiophenylenevinylenethienothiophenylenevinylene-based pB alpha CN, diketopyrrolopyrrolequaterthiophene-based P4TDPPCN, and isoindigoquaterthiophene-based P4TICN, were chosen as the interlayer to further improve the PCE of NiOx-optimized PVSCs. The polymer interlayer-containing PVSCs exhibit a PCE as high as 20.09 and 21.43% (with a device active area of 0.04 cm(2)) for P4TDPPCN and P4TICN, respectively. We have experimentally verified that charge transport resistance (R-ct), charge recombination resistance (R-rec), and trap density (n(trap)) are all reduced with the polymer interlayer in PVSCs. The contact of the MAPbI(3) perovskite to NiOx becomes better with a polymer interlayer in between. All of these enable the FF of PVSCs approaching 80%. Interestingly, the photovoltaic polymers provide additional photocurrent for the MAPbI(3) PVSCs with a high short-circuit current density (J(SC)) over 24 mA/cm(2). While MAPbI(3) failed to deposit on the pB alpha CN polymer interlayer due to a serious nonwetting issue, it was relatively problem-free for P4TDPPCN and P4TICN. In this report, we provide chemical insight to explain the successful fabrication of the perovskite material on top of the P4TDPPCN or P4TICN polymer interlayer.

Organic light-emitting diode (OLED) has gain numerous attentions since an efficient OLED was firstly demonstrated by Tang and VanSlyke in 1987. Thanks to lots of efforts paid on their progress including materials and device architecture in past three decades, red and green OLEDs have great success in efficiency and lifetime. However, the development of high efficiency deep-blue counterparts with Commission Internationale de L'Eclairage (CIE) coordinate of y<0.1 currently remains in demand in the market of full-color display applications. For example, to realize the BT.2020 color space standard, the standard blue emission must have CIE coordinates of (0.131,0.046), and that is extremely challenging, especially in material development. Here, a new compound consisting of phenyls groups to connect a benzene core was successfully synthesized. The newly obtained compound exhibited a super wide bandgap of 3.5 eV and a deep-blue emission of approximately 397 nm as well as a photoluminescence quantum yield (PLQY) by 68% in thin film. Consequently, a non-doped OLED using the pristine new compound as emitting layer showed a peak efficiency of 4.9% in external quantum efficiency (EQE) and deep-blue emission with CIE coordinates of (0.16, 0.04). Note that the OLED configuration was bottom emission, which meant the such deep-blue emission resulted from the material itself, rather than microcavity effect. Grazing incidence wide-angle X-ray scattering (GIWAXS) of new compound displayed an order parameter (SGIWAXS) of 0.44, indicating molecules primarily aligned horizontally to the substrate, which contributed to the high efficiency.

This paper mainly discusses the structure-property relationship of two donor-acceptor-donor (D-pi-A-pi-D) type dopant-free hole transporting materials (HTMs) (TPA-TPy and TPA-Py-PTZ) comprising primarily of 2,4,6-trisubstituted pyridine as the acceptor core and 4,4'-dimethoxytriphenylamine as the peripheral donor groups and their use in p-i-n perovskite solar cells (PVSCs). Compared to inferior TPA-Py-PTZ, TPA-TPy has a superior hole extraction and hole transport at the HTM/perovskite interface. The pinhole-free, smooth and dense, fully covered and well-crystallized MAPbI3 perovskite layer on TPA-TPy reduces the carrier recombination and substantially improves the short circuit current density (JSC), open circuit voltage (VOC), and the fill-factor (FF) of MAPbI3 PVSCs. The PVSC employing TPA-TPy as HTM exhibits a power conversion efficiency (PCE) of 15.33% with a JSC of 23.69 mA cm(-2), a VOC of 0.95 V, and a FF of 68.10%. Especially, both TPA-TPy and TPA-Py-PTZ PVSCs exhibit a better moisture stability than that of NiOx PVSCs. It is because of the hydrophobic nature of TPA-TPy and TPA-Py-PTZ, which enables the formation of MAPbI3 perovskite layer having a larger grain-size, a less grain boundary, and a less infiltration of moisture.

Bulk heterojunction is one key concept leading to breakthrough in organic photovoltaics. The active layer is expectantly formed of distinct morphologies that carry out their respective roles in photovoltaic performance. The morphology-performance relationship however remains stymied, because unequivocal morphology at the nanoscale is not available. We used scattering-type scanning near-field optical microscopy operating with a visible light source (visible s-SNOM) to disclose the nanomorphology of P3HT:PCBM and pBCN:PCBM blends. Donor and acceptor domain as well as intermixed phase were identified and their intertwined distributions were mapped. We proposed energy landscapes of the BHJ active layer to shed light on the roles played by these morphologies in charge separation, transport and recombination. This study shows that visible s-SNOM is capable of profiling the morphological backdrop pertaining to the operation of high performance organic solar cells.

This review article surveys the hybrid white organic light-emitting diodes (WOLEDs) based on phosphorescent platinum complexes and fluorescence blue emitters developed in the last 20 years. Emission, either photoluminescence (PL) or electroluminescence (EL), properties of the materials, and the evolution of the configuration of devices in achieving the high performance WOLEDs are elaborated in the article.

Four 1,5-naphthyridin-4-ol-containing platinum complexes, AtFOND, AtFNND, PBSOND, and PBSNND, have been synthesized and characterized for their photoluminescence (PL) and electroluminescence (EL) properties.

Two structural isomers of the bisacrylonitrilethienothiophene-benzodithiophene copolymer, pB alpha CN and pB beta CN, have been comprehensively studied by differential calorimetry, UV-visible absorption spectroscopy, cyclic voltammetry, density functional theory calculation, grazing incidence wide-angle X-ray scattering, transmission electron microscopy, fluorescence spectroscopy, and space-charge-limited current determination. We have obtained insightful information to elucidate why the beta-isomer of the copolymer (pB beta CN) can achieve a higher open-circuit voltage (0.96 V) along with a higher short-circuit current density (15.62 mA/cm(2)) and hence a higher power conversion efficiency of 9.27% than the alpha-isomer of the copolymer (pB alpha CN) in [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM)-blended bulk heterojunction polymer solar cells.

A novel bis-4Ph-substituted 9,10-dipehnylanthracene deep blue [1931 CIE (0.15, 0.08)] fluorescent compound, AnB4Ph, has been synthesized and characterized for organic light-emitting diode (OLED) applications. Our experimental study of AnB4Ph excludes the possibility of triplet-triplet annihilation, hybridized local and charge transfer, or thermally activated delayed fluorescent characteristics of the material. Since the solid-state photoluminescence quantum yield of AnB4Ph was determined to be 48%, assuming a 100% for the charge recombination efficiency, the light outcoupling efficiency (ηout) of an AnB4Ph non-doped OLED achieving an external quantum efficiency (EQE) of 5.3% is at least 44%, which is more than twofold higher than 20% for conventional OLEDs. Both grazing incidence wide-angle X-ray scattering (GIWAXS) and angle-dependent photoluminescence (ADPL) measurements reveal AnB4Ph having a high value of order parameter (SGIWAXS) of 0.61 for a ππ stacking along the normal direction and an orientation order parameter (SADPL) for a horizontal emitting dipole moment of -0.50 or Θ (horizontal-dipole ratios) of 100%, respectively. Otherwise, a refractive index (n) measurement provides a n = 1.80 for AnB4Ph thin films. Based on ηout = 1.2 × n-2, the calculated ηout is 37%, which is also in accordance with the results of GIWAXS and ADPL. We have also fabricated the classical fluorescent DPAVBi-doped AnB4Ph OLEDs, which display a true blue [1931 CIE (0.15 and 0.16)] electroluminescence with a high efficiency (EQE = 6.9%), surpassing the conventional ∼5% EQE. Based on an ηout of 42% for DPAVBi-doped AnB4Ph OLEDs, our studies suggest that the extremely horizontally aligned AnB4Ph host material exerts the same horizontal alignment on the DPAVBi dopant molecules.

Two platinum complexes PBSNND and AtFNND have been used to achieve high efficiency (EQEmax of 12.9% and 13.7%) hybrid white OLEDs with an ultrathin and singly doped phosphorescence emitting layer, respectively.

The newly developed Pb[N(CN)(2)](2) additives have been demonstrated for enhancing efficiency from 14.7% to 17.4% and from 15.5% to 18.2% for conventional (FTO/TiO2 as the substrate) and inverted (FTO/NiOx as the substrate) MAPbI(3) perovskite solar cells (PVSCs), respectively. Different from many effective additives of PVSCs, Pb[N(CN)(2)](2) provides the first visual evidences (colors changing) of additives participating in the solution adduct of MAPbI(3) precursors. Further experimental results reveal that the Pb[N(CN)(2)](2) additives slowdown the formation process of the MAPbI(3) crystallite thin film, of which the grain size reaches up to 900 nm with 0.2 M concentration of Pb[N(CN)(2)](2) additives in the MAPbI(3) precursor solutions (1 M), accordant with the optimal concentration of Pb[N(CN)(2)](2) additives in enhancing efficiency of MAPbI(3) PVSCs. We understand the role of Pb [N(CN)(2)](2) additives in MAPbI(3) PVSCs through color photos (of precursor adduct solution and the adduct solid isolated from solutions), infra-red (of adduct solid isolated from solution), UV-visible absorption, photoluminescence, static and time-dependent powder X-ray spectroscopies.

A novel platinum complex FBNNND shows rare non-aggregation in solid state and hence the same emission color both in solution and in solid state, which is drastically different from that of FPtOPhND, a classical platinum complex.

Due to the long wavelength absorption and a better morphology of the bulk heterojunction (BHJ), replacing PC71BM with the nonfullerene electron acceptor (NFA) IT4F significantly improves the power conversion efficiency (PCE) of polymer (PFT)-based binary organic photovoltaics (OPVs) from 8.1% to 10.9% with an active layer 120 nm thick. Including PC71BM in the PFT:IT4F binary OPVs, the PFT:IT4F:PC71BM ternary OPVs further enhance the PCE up to 12.9% when the blending weight ratio of PFT:IT4F:PC71BM is 1:1:0.25, for which the BHJ thickness is 120 nm. With a fine tuning of the OPV fabrication process, a high PCE of 12.4% (vs 9.24% for the binary OPV) has been achieved by devices with a thick (300 nm) BHJ, which is rare for NFA-containing polymer OPVs. We have conducted a comprehensive study, including Forster energy transfer by absorption and emission spectroscopy, thin film photoelectron spectroscopy and (electrochemical) cyclic voltammetry for the energy level of the molecular orbitals, BHJ morphology by AFM and TEM microscopy, polymer chain crystallite and alignment orientation by 2D GIWAXS, charge carrier mobility by space-charge limited current (SCLC), dynamic photoluminescence quenching for exciton dissociation, and charge recombination by light-intensity dependence of the short-circuit current density (J(SC)) and open-circuit voltage (V-OC). Accordingly, we have elucidated why the blending weight ratio of 1:1:0.25 of the ternary system is the best and why PFT:IT4F:PC71BM ternary OPVs achieve a respectful PCE with such a thick (300 nm) BHJ.

With a judicious selection of the nickel complex (precursor) and stabilizer, that is, nickel formate and enthylenediamine, respectively, a conventional sol-gel method followed by a sintering process at 450 degrees C, nanoporous NiOx (np-NiOx) thin films have been successfully prepared. However, the alcohol solvent used in the sol-gel process is critical that only low-viscosity ones, such as methanol, ethanol, 2-methoxyethanol, and iso-propanol, afford np-NiOx instead of plate/flake-like compact NiOx (cp-NiOx). Some stabilizers, such as 1,3-diaminopropane, diethylenetriamine, and N,N-dimethylethylenediamine, provide nothing but seemly amorphous NiOx fragmentary thin films, which are unsuitable for the hole-transporting material (HTM) in the inverted perovskite solar cells (PVSCs). SEM or AFM study has a clear differentiation between np-NiOx and cp-NiOx. Moreover, we have characterized that the np-NiOx thin films show a better conductivity, a higher hole mobility, a stronger perovskite photoluminescence quenching, and a superior transparency than those of cp-NiOx thin films. Using MAPbI(3), inverted PVSCs were fabricated with either np-NiOx or cp-NiOx as HTM. A high power conversion efficiency approaching 20% was achieved by np-NiOx-based PVSCs, which was better than our best PVSC (17.95%) based on cp-NiOx. Electrochemical impedance spectroscopy (EIS) has observed a lower charge recombination resistance but a higher charge transport resistance for the cp-NiOx device comparing with those of each np-NiOx devices. Moreover, np-NiOx MAPbI(3) PVSCs exhibit a less hysteresis effect and an extended lifetime in terms of shelf stability compared with those of cp-NiOx MAPbI(3) PVSCs. The SEM and XRD have demonstrated the larger grain size and less gain boundary of MAPbI(3) thin films on np-NiOx HTM, where MAPbI(3) is in fact more hydrophobic, evident by the water contact angle.

Five thieno[3,4-c]pyrrole-4,6-dione (TPD)-terthiophene copolymers, PHT, P1F3HT, P1F1HT, P3F1HT, and PFT, having 0, 25, 50, 75, and 100% of fluorine substituents on the center of terthiophene exhibit a progressive increase of open-circuit voltage (V-OC), short-circuit current density (J(SC)), and hence a power conversion efficiency (PCE) up to 9.68% of PC61 BM-blended copolymer photovoltaics, which is the highest PCE reported for TPD-based polymer solar cells with fullerene derivatives as the electron acceptor. It is evident in atomic force microscopy and transmission electron microscopy studies that the width of copolymer nanofibrils formed in solar cells decreases progressively with the increasing fluorine substituents of the copolymers. A declining solubility, which is attributed to the fluorophobic effect, narrows the nanofibril of copolymers with more fluorine substituents. Grazing incidence wide angle X-ray scattering studies reveal the improved crystallinity of lamellar stacking and pi-pi stacking structures of copolymers with more fluorine substituents. Density functional theory calculation indicates a virtually coplanar conformation of terthiophene units with fluorine substituents. The increasing V-OC is also associated with the increasing fluorine substituents, which lower the highest occupied molecular orbital energy level of the copolymers verified by the electrochemical and photoelectron spectroscopic measurements.