Search

The electrical and optical properties of the hole transport layer (HTL) are critical for organic and halide perovskite solar cell (OSC and PSC, respectively) performance. In this work, we studied the effect of Mg doping on CuCrO2 (CCO) nanoparticles and their performance as HTLs in OSCs and PSCs. CCO and Mg doped CCO (Mg:CCO) nanoparticles were hydrothermally synthesized. The nanoparticles were characterized by various experimental techniques to study the effect of Mg doping on structural, chemical, morphological, optical, and electronic properties of CCO. We found that Mg doping increases work function and decreases particle size. We demonstrate CCO and Mg:CCO as efficient HTLs in a variety of OSCs, including the first demonstration of a non-fullerene acceptor bulk heterojunction, and CH3NH3PbI3 PSCs. A small improvement of average short-circuit current density with Mg doping was found in all systems.

Stretchable thermoelectric thin films have attracted considerable attention due to their prospective applications in wearable electronics. Nevertheless, targeted resolutions are required for persistent challenges such as the increased resistance and diminished electrical conductivity under strain. The present study focuses on the development of high-performance thermoelectric nanocomposites via the blending of thienyl-phenylene-thienylene-phenylene-thienyl (TPT) nonacyclic fused ring-based conjugated polymers with single-walled carbon nanotubes (CNTs). To disperse the CNTs, three TPT-based ladder-type random conjugated copolymers featuring distinct acceptor units are investigated, namely (i) thieno[3,4-c]pyrrole-4,6(5H)-dione (TPD), (ii) diphenylquinoxaline (QX), and (iii) thieno[3,4-b]thiophene (TT). Notably, the highly planar backbone structure of TPT-TT efficiently wraps around the surfaces of the CNTs, thus facilitating their uniform dispersion within the nanocomposite film. Consequently, the TPT-TT/CNT nanocomposite exhibits superior thermoelectric properties, including a power factor (PF) of up to 678.8 mW m1 K2. In addition, stretchable thermoelectric thin films are fabricated on a poly(dimethylsiloxane) (PDMS) substrate by incorporating various amounts of the styrene-ethylene-butylene-styrene (SEBS) elastomer into the TPT-TT/CNT nanocomposite. The ternary TPT-TT/CNT/SEBS25 (containing 25 wt% SEBS) nanocomposite film maintains a PF of 372.79 mW m1 K2 (73.2% of its initial value) at 50% strain. The present study introduces a straightforward approach for fabricating stretchable thermoelectric thin films with commendable thermoelectric performance under strains of up to 50% by blending the high-performance ladder-type conjugated-polymer/CNT nanocomposite with SEBS. [ABSTRACT FROM AUTHOR]

A poly(3-hexylthiophene) (P3HT)-based inverted solar cell and indene-[C.sub.60] bis-adduct (ICBA) as the acceptor is used to accomplish a high open-circuit voltage of 0.82 V due to ICBA's higher-lying lowest unoccupied molecular orbital level. The ICBA:P3HT-based inverted device is observed to exhibit an improved short-circuit current and fill factor to yield a higher power-conversion efficiency (PCE) when a cross-linked fullerene interlayer is incorporated.

A novel PCBM-based n-type material, [6,6]-phenyl-[C.sub.61]-butyric styryl dendron ester (PCBSD), functionalized with a dendron containing two styryl groups as thermal cross-linkers, is designed and prepared. The incorporation of cross-linked [C.sub.60] interlayer has become a standard procedure in preparing highly efficient and stable multilayer inverted solar cells.

The preparation of a two-photon absorbing block copolymer that acts as a nanocarrier for porphyrin and causes energy transfer and singlet oxygen generation in micellar aqueous solutions is described. The strategy helps covalently bonded donors to trap acceptors within a nanoenvironment to improve the efficiency of oxygen generation, making the copolymers beneficial for bioapplications.

A ladder-type nonacyclic thienyl-phenylene-thienylene-phenylene-thienyl TPTPTunit, consisting of alternate interfused thiophene andbenzene units, is designed and synthesized. This multifused distannyl-TPTPTmonomer was polymerized with two electron-deficientacceptors, 4,7-dibromo-2,1,3-benzothiadiazole BTand5,8-dibromo-2,3-diphenylquinoxaline QXmonomers, by Stillecoupling reaction to afford two alternating donor–acceptorcopolymers, PTPTPTBTand PTPTPTQX, respectively.Because of the covalent planarization of the conjugated framework, PTPTPTBTsimultaneously possess excellent solubilities forsolution-processability, low bandgaps with suitable position of HOMO/LUMOenergy levels, and high hole mobilities. The devices based on the PTPTPTBT/PC71BM blend not only showed a promisingPCE of 5.3% with conventional configuration but also achieved a highPCE of 5.9% with inverted configuration. This value is among the highestperformance from the inverted solar cells incorporating a donor–acceptorlow bandgap polymer. [ABSTRACT FROM AUTHOR]

Nitrogen-bridged donor–acceptor multifused dithienopyrrolobenzothiadiazole (DTPBT) and dibenzothiadiazolopyrrolothiophene (DBTPT) were successfully synthesized by intramolecular Cadogan annulation. The electron-deficient benzothiadiazole unit in DTPBT can be converted to benzoselenadiazole and quinoxaline moieties through reduction/cyclization to generate dithienopyrrolobenzoselenadiazole (DTPBSe) and dithienopyrroloquinoxaline (DTPQX), respectively. The nitrogen atoms function as the bridges for covalent planarization to induce intermolecular interaction and intramolecular charge transfer. [ABSTRACT FROM AUTHOR]

A new class of fullerene bis-adductsdi(4-methylphenyl)methano-C60bis-adduct (DMPCBA), di(4-fluorophenyl)methano-C60bis-adduct (DFPCBA), and diphenylmethano-C60bis-adduct (DPCBA)were rationally designed and easily synthesized. Compared to the lowest unoccupied molecular orbital (LUMO) energy level of PC61BM(−3.95 eV), the double functionalization effectively raises the LUMO energy levels of these fullerene materials to ca. −3.85 eV, regardless of the substituent groups (CH3–, F–, and H−) at the para-position of the phenyl rings. This phenomenon suggests that the plane of the phenyl groups is preferentially parallel to the fullerene surface, leading to poor orbital interactions with C60and negligible electronic effect. Importantly, such geometry sterically protects and shields the core C60structure from severe intermolecular aggregation, rendering it intrinsically soluble, morphologically amorphous, and thermally stable. The device based on the P3HT:DMPCBAblend exhibited an open-circuit voltage (Voc) of 0.87 V, a short-circuit current density (Jsc) of 9.05 mA/cm2, and a fill factor (FF) of 65.5%, leading to a high power conversion efficiency (PCE) of 5.2%, which is superior to that of the P3HT:PC61BM-based device. Most significantly, the amorphous nature of DMPCBAeffectively suppresses the thermal-driven aggregation and thus stabilizes the morphology of the P3HT:DMPCBAblend. Consequently, the device retained 80% of its original PCE value against thermal heating at 160 °C over 20 h. [ABSTRACT FROM AUTHOR]

A new class of cross-linkable N,N,N′,N′-tetraphenyl-1,1′-biphenyl-4,4′-diamine (TPD)-based hole-transporting materials (HTMs), DV-OMe-TPD, DV-Me-TPD, and DV-F-TPD, were designed and synthesized. Two vinyl groups in the TPD units are used for thermal cross-linking, whereas methoxy, methyl and fluoro groups are introduced to modulate the HOMO energy levels of the HTMs. These HTMs are thermally cross-linked to overcome interfacial mixing, realizing solution-processed polyfluorene (PFO)-based devices (ITO/cross-linked HTMs/PFO/CsF/Al). Besides the characteristic blue emission of PFO, the devices exhibited a red emission whose energy is highly dependent on the HOMO energy of the cross-linked HTM used in the device. This result suggests that the red electroluminescence is derived from the exciplex generated by the adjacent hole and electron at the cross-linked HTM/fluorenone heterojunction interface. By doping small amount of 4,7-bis(9,9-dihexylfluoren-2-yl)-2,1,3-benzothiadiazole (BFBT) into the emissive layer (EML) to compensate green emission, the devices with the configuration of ITO/PEDOT:PSS/DV-Me-TPD/PFO doped with BFBT/CsF/Al exhibited white electroluminescence comprising three primary colors simultaneously. The 0.04 wt % doped device achieved a maximum luminous efficiency of 5.28 cd/A, which represents the highest efficiency for WPLEDs reported so far on the basis of the exciplex strategy. This device showed CIE chromaticity coordinates of (0.32, 0.42) which are close to the ideal white point (0.33, 0.33). We have demonstrated that integrating cross-linked triarylamine-based HTMs with fluorenone defects in PFO to induce exciplex electroluminescence can provide a useful way for realizing WPLED devices. [ABSTRACT FROM AUTHOR]

We have successfully designed and synthesized two oxetane-functionalized fullerene derivatives, [6,6]-phenyl-C61-butyric oxetane ester (PCBO) and [6,6]-phenyl-C61-butyric oxetane dendron ester (PCBOD). We demonstrated that the oxetane functionality with neutral nature can anchor onto the TiOxsurface via cationic ring-opening reaction under thermal and UV treatment, as evidenced by contact angle measurement and X-ray photoelectron spectroscopy. The self-assembly of PCBO, functionalized with one oxetane group, on the TiOxsurface forms an adhesive monolayer with intimate contact. Inverted bulk-heterojunction device B [ITO/TiOx/SA-PCBO/P3HT:PCBM (1:1 w/w)/MoO3/Ag, where ITO is indium tin oxide, SA is self-assembled, P3HT is poly(3-hexylthiophene), and PCBM is [6,6]-phenyl-C61-butyric acid methyl ester] with this self-assembled PCBO (SA-PCBO) modifier showed an impressive power conversion efficiency (PCE) of 4.1%, which outperforms the reference device A (PCE = 3.6%) without this monolayer [ITO/TiOx/P3HT:PCBM (1:1 w/w)/MoO3/Ag]. This SA-PCBO modifier exerts multipositive effects on the interface, including improvement of exciton dissociation efficiency, reduction of charge recombination, decrease of the interface contact resistance, and passivation of the surface electron traps at the interface of TiOx. Furthermore, PCBOD, containing two oxetane groups, is capable of self-assembling on the TiOxsurface and simultaneously undergoing cross-linking, generating a dense, robust, and pinhole-free multimolecular interlayer to further strengthen the interface characteristics. Device C [ITO/TiOx/C-PCBOD/P3HT:PCBM(1:1, in wt%)/MoO3/Ag] incorporating this cross-linked PCBOD (C-PCBOD) interlayer delivered the highest PCE of 4.5% which represents 26% enhancement over device A. This simple and easy strategy smartly integrates the advantages of self-assembly and cross-linking in a single fullerene-based molecule, showing promise in producing highly efficient inverted PSCs. [ABSTRACT FROM AUTHOR]

A series of phenyltetraene-based nonlinear optical (NLO) chromophores 1a–cwith the same donor and acceptor groups, but different tetraene bridges that are partly connected by various sizes of aliphatic rings, have been synthesized and systematically investigated. The interposed conjugated tetraene segments in three chromophores studied are based on isophorone, (1S)-(−)-verbenone, and 3,4,4-trimethyl-2-cyclopentenone, respectively. This kind of structural alteration has significant effect on the intrinsic electronic structures and physical properties of these highly polarizable chromophores as revealed by a variety of characterization techniques. The introduction of the verbenone- and trimethylcyclopentenone-based tetraene bridges could significantly improve the glass-forming ability of chromophores 1band 1cin comparison with the highly crystalline characteristics of isophorone-based chromophores 1a. More importantly, chromophores 1a–cexhibited distinct optical features in absorption band shape, solvatochromic behavior, as well as energy band gap from the UV-vis-NIR absorption measurements. Quantum mechanical calculations using density functional theory (DFT) were also used to evaluate second-order NLO properties of these chromophores. The electro-optic (EO) coefficients of 1a–cin poled polymers with the 10 wt% chromophore content showed an apparent decrease from 78 pm V−1for 1ato 42 pm V−1for 1c. This decrease is attributed to the gradual decrease of the molecular hyperpolarizability (β) of the chromophores which is associated with the progressive cyanine-like electronic structure from the isophorone-based 1ato the cyclopentenone-based 1cchromophore. [ABSTRACT FROM AUTHOR]

We have successfully utilized epoxyisophorone ring-opening chemistry to efficiently incorporate the butylthio group to the phenyltetraene bridge of highly efficient nonlinear optical chromophores in high overall yield. By following the guidance of Dewar’s rules, the sulfur atom functions as a moderate π-accepting group at a starred position of the conjugated bridge. Several of very critical material parameters of the phenyltetraenic chromophores for device applications have been intrinsically and simultaneously improved through such a simple and straightforward engineering of molecular structures. Compared with the nonsubstituted analogue 2, thiolated chromophore 1achieves higher molecular hyperpolarizability (34%), enhanced E-O coefficient (38%), significantly improved photochemical stability against 1O 2(by an order of magnitude), and better optical transparency (17 nm blue-shifted λ maxabsorption spectrum). [ABSTRACT FROM AUTHOR]

We examine the effects of surface ligand exchange on the performance of hybrid organic/inorganic light emitting diodes (LEDs) that use colloidal nanocrystal quantum dots as emissive centers. Using a series of primary alkylamines with different alkane chain lengths, we exchange the native surface ligands on a series of CdSe/CdZnS/ZnS core/shell/shell nanocrystal quantum dots and compare the differences in photoluminescence and electroluminescence efficiency of the emissive quantum dot layer. We fabricate LEDs made with octadecylamine-, octylamine-, and butylamine-exchanged quantum dots. We find that the differences in electroluminescence efficiency of the devices are not always proportional to the photoluminescence quantum efficiency of the quantum dots. We discuss this trend both in terms of the competing needs of high photoluminescence efficiency and good charge injection and energy transfer, and also in terms of the different processability and film morphology arising from the use of nanoparticles passivated with shorter ligands. [ABSTRACT FROM AUTHOR]

A series of novel hole-transporting materials (HTMs) bearing thermally cross-linkable styryl groups have been synthesized and characterized. These HTMs could be in situcross-linked under mild thermal polymerization without any initiator. The cross-linking temperatures (150–180 °C) for these HTMs are substantially lower than that typically used for curing perfluorocyclobutane (PFCB)-based HTMs (230 °C). After cross-linking, the resultant HTMs form robust, smooth, and solvent-resistant networks, which enables the subsequent spin-coating of emissive layer (EML). The HTMs based on an ether linkage connecting triarylamine dimers exhibited better hole-transporting ability compared to their corresponding monotriarylamine compounds due to higher content and closer distance of the hole-transporting units. Most importantly, the milder cross-linking condition for these HTMs allows the commonly used conducting polymer, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS), to be incorporated as the bottom hole-injecting layer to improve turn-on voltage and power efficiency of the devices. This PEDOT/HTM double-layer hole-injecting/hole-transporting configuration also provides the combined advantages of preventing acidic PEDOT:PSS-induced quenching of emission, facilitating cascade hole injection and transport, and functioning as an efficient electron blocker. One of the devices that combines 2-NPD with PEDOT:PSS showed much improved performance of low turn-on voltage (3.3 V), high luminous efficiency (10.8 cd/A), and brightness (21 500 cd/m 2). [ABSTRACT FROM AUTHOR]

Silylene-spaced copolymers with alternating azacrown and anthracene moieties were synthesized for photoinduced electron transfer investigations. These polymers exhibited efficient intrachain photoinduced electron transfer with charge separation yield about 0.96−0.99 and corresponding charge-transfer rates around 10.8−32.2 ns-1in different solvents. Metal cations have been shown to enhance the fluorescence intensity due to complexation. These results are comparable to those of small molecules having similar chromophores. The geminal dimethyl substituents on silicon in these copolymers may direct the relative conformation (or distance) of the remaining substituents on silicon. Intrachain interactions between these chromophores may readily take place leading to highly efficient electron transfer processes. [ABSTRACT FROM AUTHOR]

Two series of highly efficient and thermally stable nonlinear optical chromophores based on the (4-diarylamino)phenyl electron donors have been synthesized and systematically investigated. A modular approach has been employed to synthesize these electron donors with tunable size, shape, and electron-donating abilities. Efficient conjugated bridges were extended from these donors and coupled with very strong CF3−TCF electron acceptors to afford chromophores with very high values (up to 7077 × 10-30esu at 1.907 m). These chromophores possess much higher thermal stability (with their onset decomposition temperatures all above 220 °C) than those substituted with (4-dialkylamino)phenyl donors. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into very large electro-optic (E-O) coefficients (r33) in poled polymers through suitable shape engineering. Exemplified by the chromophore B4, which has a fluorinated aromatic substituent anchored at its donor end, it showed a very large r33(169 pm/V) at 1.31 m. This value is almost 1 order higher than the E-O activities usually reported for (4-diarylamino)phenyl-substituted NLO chromophores. [ABSTRACT FROM AUTHOR]

A poly(3-hexylthiophene) (P3HT)-based inverted solar cell using indene-C60 bis-adduct (ICBA) as the acceptor achieved a high open-circuit voltage of 0.82 V due to ICBA's higher-lying lowest unoccupied molecular orbital level, leading to an excep- tional power-conversion efficiency (POE) of 4.8%. By incorporat- ing a cross-linked fullerene interlayer, C-PCBSD, to further modulate the interface characteristics, the ICBA:P3HT-based inverted device exhibited an improved short-circuit current and fill factor, yielding a record high PCE of 6.2%. [ABSTRACT FROM AUTHOR]

Construction of a phenanthrodithiophene diimide core has been accomplished through photo-induced 6π electrocyclization. It is generated with the formation of anthradithiophene diimide. The product distribution is illuminated by the help of DFT calculations. The discrepancy in the optical and electrochemical properties between both compounds is identified. Time-dependent DFT calculations are carried out, yielding theoretical UV-vis spectra, which agree well with the experimental patterns. Electronic transitions for the two compounds can be clarified. Overall, this study provides a new synthetic approach to accessing phenanthrodithiophene diimide and elucidates the reaction mechanism and optical and electrochemical properties. [ABSTRACT FROM AUTHOR]