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Electroluminescence (EL) from the singlet-excited (S

The device efficiency of

In this paper, we describe the application of the enantiomeric compounds

A series of NIR-II fluorescent TADF-incorporated polymer dots were successfully synthesized. The function of the TADF moiety was fully studied and the bio-applications of these polymer dots including bone imaging were also demonstrated.

In this paper, two D-π-D type compounds, C1 and C2, containing dihydrodinaphthopentacene (DHDNP) as a π-bridge, p-methoxydiphenylamine and p-methoxytriphenylamine groups as the donor groups were synthesized. The four 4-hexylphenyl groups at the sp3 -carbon bridges of DHDNP were acquainted with control morphology and improving solubility. The light absorption, energy level, thermal properties, and application as hole-transporting materials in perovskite solar cells of these compounds were fully investigated. The HOMO/LUMO levels and energy gaps of these DHDNP-based molecules are suitable for use as hole-transporting materials in PSCs. The best power conversion efficiencies of the PVSCs based on the C1 and C2 are 15.96% and 12.86%, respectively. The performance of C1 is comparable to that of the reference compound spiro-OMeTAD (16.38%). Compared with spiro-OMeTAD, the C1-based PVSC device showed good stability, which was slightly decreased to 98.68% of its initial efficiency after 48 h and retained 81% of its original PCE after 334 h without encapsulation. These results reveal the potential usefulness of the DHDNP building block for further development of economical and highly efficient HTMs for PVSCs.

Nitrate (NO3-) reduction reaction (NtRR) is considered as a green alternative method for the conventional method of NH3 synthesis (Haber-Bosch process), which is known as a high energy consuming and large CO2 emitting process. Herein, the copper nanodendrites (Cu NDs) grown along with the {200} facet as an efficient NtRR catalyst have been successfully fabricated and investigated. It exhibited high Faradaic efficiency of 97% at low potential (-0.3 V vs RHE). Furthermore, the 15NO3- isotope labeling method was utilized to confirm the formation of NH3. Both experimental and theoretical studies showed that NtRR on the Cu metal nanostructure is a facet dependent process. Dissociation of NO bonding is supposed to be the rate-determining step as NtRR is a spontaneously reductive and protonation process for all the different facets of Cu. Density functional theory (DFT) calculations revealed that Cu{200} and Cu{220} offer lower activation energy for dissociation of NO compared to that of Cu{111}.

In this study, we achieved a facile and low-cost (18-22 USD/g) synthesis of spiro[fluorene-9,9-phenanthren-10-one]-based interfacial layer materials (MSs; designated MS-PC, MS-PA, MS-OC, and MS-OA). Carbazoles and dimethylacridine substituents with an extended π-conjugation achieved through ortho- or para-orientations were used as donors at the spiro[fluorene-9,9'-phenanthren-10'-one] moiety. Highly efficient and stable inverted perovskite solar cells (PSCs) with the device architecture of ITO/NiOx/MSs/perovskite/PC61BM/BCP/Ag can be achieved to improve the surface morphology of NiOx when MSs are adopted as the interfacial layer. During a morphological study, the ortho-orientated donor of MS-OC and MS-OA has spherical structures indicated that the films were smooth and that the films of perovskite deposited on them had large grain size and uniformity. The photoluminescence properties of the perovskite layers on the NiOx/MSs were showed better hole-transporting capabilities than the bare NiOx. The dual-functional interfacial layer has shown defect passivation effect, it not only improved the surface morphology of NiOx but also enlarged the perovskite layer grain size. The best PSC device performance of the NiOx/MS-OC was characterized by 22.34 mA cm-2 short-circuit current density (Jsc), 1.128 V open-circuit voltage (Voc), and 80.8% fill factor (FF), resulting in 20.34% power conversion efficiency (PCE). The NiOx/MS-OC PSCs showed good long-term device stability, even retained the original PCE of 93.16% after 370 days under argon (25 °C). Owing to the superior perovskite morphologies of the NiOx/MSs, the resulting devices outperformed the bare NiOx-based PSCs.

Organic–inorganic hybrid lead perovskite films are crucial in perovskite solar cells (PSCs). However, a solution deposition process rendered a polycrystalline feature to perovskite films with a large number of ionic defects on the surface and grain boundaries, which will serve as non-radiative recombination centers, limiting the photovoltaic performance of PSCs. In this work, D–A–π–A-type organic sensitizers (MM-3 and MM-4) with a quinoxaline moiety were employed to enhance light harvesting and reduce the trap states of perovskite films. MM-4 of the D–A–π–A system dye has a more coplanar structure because it contains a thiophene π-bridging moiety, which would facilitate electron transfer in molecules, enrich electron density on the terminal carboxyl group and provide good condition for coordination with undercoordinated Pb2+, resulting in the reduction of trap states and suppression of the non-radiative recombination in perovskite films. Therefore, there was a significant increase in the open-circuit voltage (VOC) from 1.02 to 1.08 V, and PCE increased from 18.91% to 20.31%. Furthermore, the long alkyl chains will enhance the hydrophobicity of perovskite films, and PSCs passivated by MM-4 exhibited excellent stability without encapsulation. It can maintain about 92% of initial PCE under 15 ± 5% relative humidity after 70 days and over 77% of initial PCE under 50–60% relative humidity after 550 h. We demonstrate that the D–A–π–A sensitizer can be another passivator for effectively passivating the trap states, which significantly improve the PCE and device durability.

The Haber–Bosch process is widely used to convert atmospheric nitrogen (N2) into ammonia (NH3). However, the extreme reaction conditions and abundant carbon released by this process make it important to develop a greener NH3 production method. The electrochemical nitrogen reduction reaction (NRR) is an attractive alternative to the Haber–Bosch process. Herein, we demonstrated that molybdenum sulfide on nickel foil (1T-MoS2–Ni) with low crystallinity was an active NRR electrocatalyst. 1T-MoS2–Ni achieved a high faradaic efficiency of 27.66% for the NRR at −0.3 V (vs. RHE) in a LiClO4 electrolyte. In situ X-ray diffraction and ex situ X-ray photoemission analyses showed that lithium ions were intercalated into the 1T-MoS2 layers during the NRR. Moreover, theoretical calculations revealed the differences between six membered rings formed in the 1T-MoS2 and 2H-MoS2 systems with Li intercalation. The bond distances of d(Mo–N) and d(N–Li) of in Li–1T-MoS2 were found to be shorter than those in Li–2H-MoS2, resulting in a lower energy barrier of N2 fixation and higher NRR activity. Therefore, 1T-MoS2–Ni is promising as a scalable and low-cost NRR electrocatalyst with lower power consumption and carbon emission than the Haber–Bosch process.

Intensive energy demand urges state-of-the-art rechargeable batteries. Rechargeable aluminum-ion batteries (AIBs) are promising candidates with suitable cathode materials. Owing to high abundance of carbon, hydrogen, and oxygen and rich chemistry of organics (structural diversity and flexibility), small organic molecules are good choices as the electrode materials for AIB. Herein, a series of small-molecule quinone derivatives (SMQD) as cathode materials for AIB were investigated. Nonetheless, dissolution of small organic molecules into liquid electrolytes remains a fundamental challenge. To nullify the dissolution problem effectively, 1,4-benzoquinone was integrated with four bulky phthalimide groups to form 2,3,5,6-tetraphthalimido-1,4-benzoquinone (TPB) as the cathode materials and assembled to be the AI/TPB cell. As a result, the Al/TPB cell delivered capacity as high as 175 mA h/g over 250 cycles in the urea electrolyte system. Theoretical studies have also been carried out to reveal and understand the storage mechanism of the TPB electrode.

Novel donor-acceptor dyads containing [2.2]- and [3.3]paracyclophane (PCP) as the bridging moiety were synthesized and used to effectively fabricate dye-sensitized hydrogen production systems. All the prepared compounds had a phenothiazine and a cyanoacrylic acid/pyridinyl acrylonitrile moiety acting as an electron donor and acceptor, respectively. Although cyclic voltammetry measurements showed similar electron-donating properties among all the synthesized dyads, the lowest absorption energy of the [2.2]PCP moiety was lower than that of the [3.3]PCP one; this was due to its shorter distance between benzene rings, which could effectively drive the charge transfer between the donor and acceptor chromophores. Under visible light (395 nm), a dyad-loaded photocatalyst in a 0.5 M aqueous glycerol solution generated detectable hydrogen gases. The optimal turnover number and photocurrent order exhibited the same trend as the hydrogen production rate since the suggested number of excited photons played a critical role in hydrogen production.

The development of optical organic nanoparticles (NPs) is desirable and widely studied. However, most organic chromophores are water-insoluble, and therefore, the derivatization and modification of these chromophores are difficult. Herein, we demonstrated a simple platform for the fabrication of organic nanoemitters by loading ten different organic dyes (molar masses of 479.1-1081.7 g/mol) into water-soluble polymer nanosponges composed of poly(styrene-alt-maleic acid) (PSMA). This nanolization strategy enables the incorporation of small commercial dyes (3.7–50% loading) and newly synthesized large photosensitive molecules (> 85% loading) into PSMA NPs and prevents the spontaneous aggregation of these hydrophobic chromophores in aqueous solutions. These low-cytotoxicity organic nanoparticles exhibited tunable red to near-infrared fluorescence emission for cellular imaging and biological tracking in vivo. Moreover, PSMA NPs loaded with designed NIR-photosensitive molecules were fabricated, and photodynamic therapy with these dye-loaded PSMA NPs for the photolysis of cancer cells was achieved when coupled with 808 nm laser excitation. Indeed, our work demonstrates a facile approach for increasing the biocompatibility and stability of organic dyes by loading them into water-soluble polymer-based carriers, providing a new perspective of organic optoelectronic materials in biomedical theranostic applications.

Nitrate (NO

In this study, we synthesized four acceptor-donor-acceptor type hole-transporting materials (HTMs) of SY1-SY4 for an HTMs/interfacial layer with carbazole as the core moiety and ester/amide as the acceptor unit. These HTMs contain 4-hexyloxyphenyl substituents on the carbazole N atom, with extended π-conjugation achieved through phenylene and thiophene units at the 3,6-positions of the carbazole. When using amide-based HTMs SY2 as a dopant-free HTM in a p-i-n perovskite solar cell (PSC), we achieved a power conversion efficiency (PCE) of 13.59% under AM 1.5G conditions (100 mW cm-2); this PCE was comparable with that obtained when using PEDOT:PSS as the HTM (12.33%). Amide-based SY2 and SY4 HTMs showed a larger perovskite grain than SY1 and SY3 because of the passivation of traps/defects at the grain boundaries and stronger interaction with the perovskite layer. In further investigation, we demonstrated highly efficient and stable PSCs when using the dopant-free p-i-n device structure indium tin oxide/NiOx/interfacial layer (SY-HTMs)/perovskite/PC61BM/BCP/Ag. The interfacial layer improved the PCEs and large grain size (micrometer scale) of the perovskite layer because of defect passivation and interface modification; the amide group exhibited a Lewis base adduct property coordinated to Ni and Pb ions in NiOx and perovskite, bifacial defect passivation and reduced the grain boundaries to improve the crystallinity of the perovskite. The amide-based SY2 exhibited the stronger interaction with the perovskite layer than that of ester-based SY1, which is related to the observations in X-ray absorption near edge structure (XANES). The best performance of the NiOx/SY2 device was characterized by a short-circuit current density (Jsc) of 21.76 mA cm-2, an open-circuit voltage (Voc) of 1.102 V, and a fill factor of 79.1%, corresponding to an overall PCE of 18.96%. The stability test of the PCE of the NiOx/SY2 PSC device PCE showed a decay of only 5.01% after 168 h; it retained 92.01% of its original PCE after 1000 h in Ar atmosphere. Time-resolved photoluminescence spectra of the perovskite films suggested that the hole extraction capabilities of the NiOx/SY-HTMs were better than that of the bare NiOx. The superior film morphologies of the NiOx/SY-HTMs were responsible for the performances of their devices being comparable with those of bare NiOx-based PSCs. The photophysical properties of the HTMs were analyzed through time-dependent density functional theory with the B3LYP functional.

In this study, we synthesized three simple and inexpensive (34–120 USD/g) 3,3′-bicarbazole-based hole transporting materials (BC-HTMs; NP-BC, NBP-BC and PNP-BC) through a metal-free oxidative coupl...

Series of metal-free dyes (OMS4-7) featuring a dibenzofulvene connected with thienyl or furanyl as conjugation bridge, T-shaped diarylamines (diphenylamine or phenyl-1-naphthylamine) as donors and different numbers of cyanoacrylic acid as anchors have been synthesized and applied into dye-sensitized solar cells (DSSCs). The efects of different donors, conjuation segments and number of anchors on optical and photovoltaic properties were investigated through photophysics, electrochemical and photovoltaic measurements. Of the DSSCs, the structure contains mono anchor with thienyl dibenzofulvene linked to diphenylamine, i.e. OMS4-based device exhibited the highest power conversion efficiency (PCE) of 2.42%, a value of Jsc of 6.01 mA cm−2, a Voc of 0.63 V, and a fill factor of 0.63 under 10 mM CDA co-adsorbent and AM 1.5 irradiation. The corresponding device was also conducted with respect to different light intensity such as D65, CWF and TL84. As a result, the cell performance based on TL84 with 2500 lx exhibited the best PCE of 8.78%.

In this study, we achieved a facile and low-cost (18-22 USD/g) synthesis of spiro[fluorene-9,9-phenanthren-10-one]-based interfacial layer materials (

Further boosting the power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) without excessively increasing production expenses is critical for practical applications. Here, we introduce silicon quantum dots (SiQDs) to enable perovskites to harvest additional sunlight without changing PSC processes. These SiQDs can convert shorter wavelength excitation light (300–530 nm) into visible region light and reflect longer wavelength perovskite-unabsorbed visible light (550–800 nm), leading to broadband light absorption enhancement in PSCs. As a result, the SiQD-based photocurrent gain can improve the external quantum efficiencies of PSCs over a wide wavelength range of 360–760 nm, yielding relatively enhanced short-circuit current density (+1.66 mA/cm2) and PCE (+1.4%). Surprisingly, even the PSC with a low-purity perovskite layer shows an ultrahigh PCE improvement of 5.6%. Our findings demonstrate QD-assisted effects based on earth-abundant and environmentally friendly silicon, leading to effective optical management that remarkably promotes the performance of PSCs and enables the balance of costs to be substantially addressed. A sunlight management strategy in perovskite solar cells (PSCs) using silicon quantum dots (SiQDs) is proposed. Due to the reabsorption of visible light induced by SiQDs, the external quantum efficiency spectra of PSCs in a wide wavelength range of 360–760 nm is significantly improved, resulting in facilitated photocurrent collection and enhanced performance of SiQD-based PSCs. Combining new and traditional solar cell materials improves the efficiency of energy conversion. Perovskites, materials with the same type of crystal structure as calcium titanium oxide, have become recognized as excellent materials for photovoltaics in particular. The ideal solar cell must optimize the amount of electrical power generated as a fraction of the solar energy striking its surface. However, most semiconductors only absorb a small proportion of the light, and this limits efficiency. A Japan-Taiwan cooperation team led by Kazuhito Tsukagoshi (National Institute for Materials Science), Chun-Wei Chen (National Taiwan University) and colleagues added silicon nanoparticles to perovskite solar cells to absorb a broader spectrum of light and thus improve its performance. In total, silicon nanoparticles can convert the shorter wavelength light to perovskite abosorbable range, and also reflect the visible light into perovskites.

Intensive energy demand urges state-of-the-art rechargeable batteries. Rechargeable aluminum-ion batteries (AIBs) are promising candidates with suitable cathode materials. Owing to high abundance of carbon, hydrogen, and oxygen and rich chemistry of organics (structural diversity and flexibility), small organic molecules are good choices as the electrode materials for AIB. Herein, a series of small-molecule quinone derivatives (SMQD) as cathode materials for AIB were investigated. Nonetheless, dissolution of small organic molecules into liquid electrolytes remains a fundamental challenge. To nullify the dissolution problem effectively, 1,4-benzoquinone was integrated with four bulky phthalimide groups to form 2,3,5,6-tetraphthalimido-1,4-benzoquinone (TPB) as the cathode materials and assembled to be the AI/TPB cell. As a result, the Al/TPB cell delivered capacity as high as 175 mA h/g over 250 cycles in the urea electrolyte system. Theoretical studies have also been carried out to reveal and understand the storage mechanism of the TPB electrode.

The synthesis, structure, physical properties, and electrocatalytic hydrogen production of tetrathiatetracene ligand based [FeFe]-hydrogenase mimic molecules were investigated. By adjusting the amount of iron, mono- and bis-[FeFe] coordinated complexes 1 and 2 were synthesized. The structures of 1 and 2 were analysed by NMR, IR, and absorption spectroscopies, and cyclic voltammetry and DFT computational analysis. In the DFT electron density maps, the HOMOs and LUMOs were located at tetrathiatetracene units, indicating that these complexes retain mainly acene characteristics. When weak acid Et3NHBF4 was added to CH2Cl2 solutions of 1 or 2, the reduction potential of iron complexes was shifted to more positive values proportional to the concentration of acid. As the acid concentration increased, the current of the reduction wave also increased, indicating the occurrence of a catalytic proton reduction reaction. The bulk electrolysis reaction showed 65.8 TON for 1 and 52.8 TON for 2.

Borane-based complexes have attracted considerable attention as thermally activated delayed fluorescence (TADF) emitters because of their thermal stability, high fluorescence efficiency, and favourable carrier mobility. In this work, we provide a facile way for borylated compounds to enable the spatially adjacent electron donor and acceptor groups to form a near-orthogonal configuration, generating an extremely small energy gap between triplet and singlet excited states (ΔEST, ∼30 meV). We demonstrate here a new series of donor-acceptor-donor borylated compounds using functional acridan derivatives as the electron donors and dimesitylborane as the acceptor moieties, which easily generates an intramolecular charge transfer upon excitation. All compounds achieved strong TADF emission and were used as dopants to fabricate TADF OLEDs. Yellow-emitting devices A and B yielded maximum efficiencies of 7.6% (22.2 cd/A) and 10.1% (32.2 cd/A), respectively. Moreover, the green-emitting device C achieved a maximum efficiency of 19.3% (56.8 cd/A) and subsequently dropped to 18.2% (53.6 cd/A) at luminance levels of 102 cd/m2. Overall, the high electroluminescent (EL) efficiencies, together with mitigated efficiency roll-off, illustrate that these compounds have a high potential for EL applications.

One of the important features of dye-sensitized solar cells (DSCs) is that their performance is relatively unaffected by lighting conditions, e.g., lighting angles and lighting intensity, which makes them ideal for application in indoor light environments. While most of past research on DSCs has focused on their performance under one-sun conditions, the effect of the structure of the dye on device performance under indoor lights has not been studied before. For this study, we designed a series of organic dyes with donor-π-bridge-acceptor (D-π-A) structure that can be synthesized in three reaction steps from inexpensive raw materials. The photophysical and electrochemical properties of the dyes and the device characteristics of the DSCs employing these dyes under indoor light (LED and T5 lamp, 600 lux) were investigated. In our research, the best PCE value of DSCs under LED lamps was 12.21% when TKU-6 was used as the sensitizer (70.8% of N719). Under T5 lamps, it was 13.43% when TKU-4 was used as the sensitizer (68.5% of N719). Moreover, we proposed the structural design strategies for dyes for high performance DSCs under indoor lights based on the type of π-bridge, the number of alkyl chains and the absorption spectrum of the dye.

In the present study, the nanocrystalline Zn2SnO4 dopen with Sr2+/Ba2+ ions is synthesized via a hydrothermal method and their structure is analyzed in detail. Moreover, the photovoltaic properties of dye-sensitized solar cells composed of doped Zn2SnO4 are investigated. The enlarged energy difference between the conduction band edge of Zn2SnO4 and the lowest unoccupied molecular orbit (LUMO) of dye gives rise to the enhanced driving force for electron injection. The DSCs based on Sr2+/Ba2+ doped Zn2SnO4 improve the power efficiency through enhancing charge transport processes and reducing recombination rates. Compared to the photovoltaic conversion efficiency of pure Zn2SnO4 cells, the DSCs based on ZTO-Sr (3.0) exhibit a greater power conversion efficiency of 4.91%. As a consequence, the device of ZTO-Ba (1.5) also demonstrates an improved efficiency of up to 4.94%. This corresponds to an enhancement in power conversion efficiency of 17%, respectively, relative to control devices.

Six novel small molecules containing phenothiazine as the core moiety of p-type materials were synthesized in combination with PC 61 BM or PC 71 BM as n-type materials for bulk heterojunction organic photovoltaic (OPV) cells. Phenothiazine was used as donor building blocks to construct acceptor–donor–acceptor (A–D–A) and A–D–D–A small molecule. We investigated the relationship between the molecular structures, optoelectronic and thermal properties, and their blend film morphologies for OPV applications. We further studied their photophysical properties using a time-dependent density functional theory model and the B3LYP functional. A solution-processed OPV employing PT2-DE combined with the electron acceptor PC 61 BM and additive DIO achieved optimal device performance, with a short-circuit current of 6.3 mA cm −2 , an open-circuit voltage of 770 mV, a fill factor of 0.55, and a corresponding overall conversion efficiency of 2.64%. To the best of our knowledge, this is the best-reported performance of a phenothiazine derivative for OPV application.

Fabrication of vacuum deposited small molecules organic solar cell with open-circuit voltage ( V oc ) exceeding 1 V is crucial in advancing the applications of organic photovoltaics (OPVs). Here, a novel carbazole-based donor-π bridge-acceptor (D-π-A) of p-type material (F-series) in combination with fullerene derivative C 60 or C 70 as n-type material for bulk-heterojunction OPVs with the structure of ITO/MoO 3 (15 nm)/F-series donor: C 60 or C 70 (40 or 80 nm)/BCP (7 nm)/Ag (120 nm) have been proposed. The vacuum deposited small molecules OPV with the donor layer consisting of F1 combined with the electron acceptor C70 exhibits a high power conversion efficiency (PCE) of 4.93%. The higher PCE of the OPV is attributed to the large V oc value of 1.02 V. The analysis of photophysical properties using a time-dependent density functional theory model and the B3LYP functional corroborates the experimental results and provides the evidence on increasing the V oc of OPVs.

A series of Y-shaped sensitizers incorporating quinoxaline or quinoxalinoid moieties were prepared and applied in dye-sensitized solar cells (DSSCs). By the introduction of quinoxalinoid functionalities, the absorption extinction coefficients could be enhanced. The molecular structures were modified by introducing an extra acceptor group (A) between a donor (D) and a π-bridge (D-A-π-A) and also by incorporating electron-donating substituents at various positions of the quinoxalinoid moiety. Some of the dyes and mixtures thereof were found to exhibit good light-harvesting efficiencies under both sunlight and indoor light, with efficiencies up to 7.92 % under one sun (AM 1.5G). When operated under indoor light, the efficiency could be boosted to 27.76, 28.74, and 30.45 % under 600, 1000, 2500 lux illumination, respectively. The best performance could be ascribed partly to an improved dye coverage on the TiO2 surface.

To develope an alternative efficient hole-transporting materials (HTMs) to 2,2′,7,7′,-tertrakis(N,N-p-dimethoxyphenylamino)-9,9′-spirobifuorene (spiro-OMeTAD) for high performance perovskite solar cells (PSCs), we demonstrate a series of donor-π-donor HTMs (WS-1, WS-2, and WS-4 HTMs) with [2.2]paracyclophane ([2.2]PCP) as the core structure and triphenylamine as four arms at pseudo-para and pseudo-ortho orientations. Compared with the well-known HTM of spiro-OMeTAD, WS-HTMs has a simpler synthetic route and short synthesis steps (3–4 steps). Due to the improved hole mobility and good charge transfer efficiency of pseudo-para-[2.2]PCP HTMs (WS-1 and WS-2), the out-of-plane carrier transport is enhanced and the PSC base on WS-1/WS-2 HTMs achieve higher Jsc and ff values than the device based on pseudo-ortho-[2.2]PCP HTM (WS-4). A SnO2 electron transport layer (ETL) with WS-1 HTM shows the best power conversion efficiency of 19.13% in a PSC, which is higher than that of spiro-OMeTAD (17.71%) under the same conditions. The WS-HTMs also provided better stability and moisture resistance in PSCs, which prolongs the lifetime in the ambient environment than in case of spiro-OMeTAD.

Four novel organic dyes (H-1, H-2, H-3, H-4) containing phenyl-thiophenyl-thiophenyl as a bridge unit were synthesized and effectively used for the fabrication of dye-sensitized solar cells (DSSCs). In both compounds, a triarylamine moiety and cyanoacrylic acid function as an electron donor and an electron acceptor, respectively. H-1 and H-3 exhibited high interaction between lithium ions and [3.3]paracyclophane, resulting in low charge recombination and high open-circuit voltage (Voc). When deoxycholic acid was used as a coadsorbent, the optimal device performance was observed in H-3, involving a short-circuit current of 16.96 mA cm−2, a Voc of 705 mV, and a fill factor of 0.64, which correspond to an overall conversion efficiency of 7.55%. Photophysical properties were analyzed using a time-dependent density functional theory model and the B3LYP functional. Furthermore, the electronic characteristics of the DSSCs were determined using electrochemical impedance spectroscopy and controlled intensity-modulated photospectroscopy.

Herein, eight metal-free organic dyes (YH-1–YH-8) containing olefin or acetylene as π-spacer linkages in a triarylene bridge were synthesised. Moreover, two dyes (1N-PPP and 1N-PPS) without olefin and triple bonds as π-spacer linkages were used as references. The photophysical and electrochemical properties of the dyes were characterised, and the dyes were then used to fabricate dye-sensitised solar cells (DSSCs). We demonstrated the use of a D–π–A dipolar system by employing arylamine derivatives as an electron donor, triarylene with iterative olefin or acetylene as a π-bridge, and cyanoacrylic acid as an electron acceptor. YH-1 had olefin as a repeating unit in the triarylene bridge and exhibited broad absorption, favourable short-circuit photocurrent density (Jsc), and favourable open-circuit voltage (Voc) when used in a film morphology with DCA as a coabsorbent. The optimal device exhibited a Jsc of 16.23 mA cm−2, a Voc of 650 mV, and a fill factor of 0.67, corresponding to an overall conversion efficiency of 7.08%. The photophysical properties of the DSSCs were analysed using time-dependent density functional theory with the B3LYP functional.

Six novel organic dyes (RY1∼RY6) containing spiro[fluorene-9,9′-phenanthren]-10′-one as an auxiliary acceptor were synthesised and effectively used for the fabrication of D-A-π-A type dye-sensitized solar cells (DSSCs). The molecular structures were modified by introducing a novel spiro[fluorene-9,9′-phenanthren]-10′-one auxiliary acceptor group between the donor and the π-bridge. The molecular rigidity can be enhanced by depressing intermolecular aggregation and carbonyl group can trapping the Li+ or I3− ions to retard the charge recombination. The sensitizer RY3 was found to perform remarkable light-harvesting efficiency of 6.30% at AM1.5 solar condition and 21.67% at TL84 (2500 lux) illuminations without DCA co-deposition. For further improvement, a higher efficiency can be achieved through a suitable co-sensitization of N719 and RY3, which displayed an efficiency of 8.55% under one sun (AM 1.5). While operated under indoor light, the efficiency was boosted to 25.57% and 27.04% at 1000 & 2500 lux illuminations, respectively. The high performance of co-sensitization of N719 and RY3 can be ascribed to a high surface coverage and a broader range of absorption wavelength. Stability test of the device co-sensitized with N719 and RY3 showed a mild decay of PCE 3.74% after 96 h, while it retained 84.49% of its original PCE after 336 h in ambient atmosphere without encapsulation.

This is the first report of donor-acceptor-donor (D-A-D) hole-transporting materials (HTMs) with spiro linkage in perovskite solar cells (PSCs). We demonstrated two novel D-A-D type HTMs with spiro[fluorene-9,9′-phenanthren-10′-one] as the core structure. Yih-series HTMs achieved low cost, high yield, and ease of operation. Yih-2 achieved slightly higher R s , and R sh , and hole mobility can enhance the performance of PSCs. Yih-2 exhibited higher Voc and. Z, than did Yih-l. We discuss the photovoltaic performance of PSCs. Consequently, Yih-2 as an HTM in PSCs achieved J sc of 22.18 mA.cm−2, V oc of 1.02 V, and fill factor of 0.71, corresponding to an overall conversion efficiency of 16.06%, which was similar to that of spiro-OMeTAD (16.08%). The photophysical properties of HTMs were analyzed through time-dependent density functional theory with the B3LYP functional.

We have demonstrated two novel donor-acceptor-donor (D-A-D) hole-transport material (HTM) with spiro[fluorene-9,9'-phenanthren-10'-one] as the core structure, which can be synthesized through a low-cost process in high yield. Compared to the incorporation of the conventional HTM of commonly used 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD), the synthesis process is greatly simplified for the presented D-A-D materials, including a minimum number of purification processes. This results in an increased production yield (>55 %) and suppressed production cost (

A new class of hole-transport materials (HTMs) based on the bimesitylene core designed for mesoporous perovskite solar cells is introduced. Devices fabricated using two of these derivatives yield higher open-circuit voltage values than the commonly used spiro-OMeTAD. Power conversion efficiency (PCE) values of up to 12.11% are obtained in perovskite-based devices using these new HTMs. The stability of the device made using the highest performing HTM (P1) is improved compared with spiro-OMeTAD as evidenced through long-term stability tests over 1000 h.

To obtain a broad spectral response in the visible region, TiO2 film is co-sensitized with a porphyrin dye (FNE57 or FNE59) and an organic dye (FNE46). It is found that the stepwise co-sensitization in one single dye solution followed by in another single dye solution is better than the co-sensitization in a cocktail solution in terms of photovoltaic performance. The stepwise co-sensitization first with a porphyrin dye and then with an organic dye outperforms that in a reverse order. DSSC devices based on co-sensitizers FNE57 + FNE46 and FNE59 + FNE46 with a quasi-solid-state gel electrolyte generate power conversion efficiencies of 7.88% and 8.14%, respectively, which exhibits remarkable efficiency improvements of 61% and 35%, as compared with devices sensitized with the porphyrin dyes FNE57 and FNE59, respectively. Co-sensitization brings about a much improved short-circuit photocurrent due to the complementary absorption of the two sensitizers. The observed enhancement of incident monochromatic photon-to-electron conversion efficiency from individual dye sensitization to co-sensitization is attributed to the improved charge collection efficiency rather than to the light harvesting efficiency. Interestingly, the open-circuit photovoltage for the co-sensitization system comes between the higher voltage for the porphyrin dye (FNE57 or FNE59) and the lower voltage for the organic dye (FNE46), which is well correlated with their electron lifetimes. This finding indicates that not only the spectral complementation but also the electron lifetime should be considered to select dyes for co-sensitization.

Organic dipolar compounds containing a 1,3-indandione-5,6-dicarboxylic acid moiety as an electron acceptor group were examined for the feasibility of using as the light harvesting material in dye-sensitized solar cells. Two compounds with triphenylamine donor moieties were synthesized by attaching it to 1,3-indandione-5,6-dicarboxylic acid. The device made with these simple dyes achieved a quantum yield up to 2.5 %, which is comparable to the widely used dye made with cyanoacrylic acid. The spectroscopic properties of these compounds were analysed with the aid of theoretical models according to the time-dependent density functional theory.

Novel ferrocene–oligothiophenylene–cyanoacrylic acid in the form of donor–spacer–acceptor dyads was synthesized. The compound with a single unit of thiophenylene showed the lowest energy transition in neutral state. For radical cations, the lowest energy transition appears red-shifted along with the increased number of thiophenylene units. These results suggested that the electronic structure of radical cations is significantly different from that of neutral molecules.

The [4+2] cycloaddition of hexacene and C60 yielded 1:1 and 1:2 adducts. The highest yield of 1:1 adduct was 90% by heating hexacene and C60 in toluene. The formation of 2 was achieved by reacting 1 with an excess amount of C60 in the presence of silica gel 60 with a yield up to 69%. The function of silica gel was rationalized by the effect of concentration enhancement inside the pore of silica gel. The reaction was examined systematically by changing the parameters of solvent, temperature, reaction time, and the pore size of silica gel. Both purified compounds 1 and 2 can be used for the fabrication of bulk heterojunction solar cells.

Alkoxyphenyl-substituted carbazole-based metal-free organic dyes were synthesized and effectively used for dye-sensitized, visible-light-driven, photocatalytic hydrogen production. Photocatalytic hydrogen production was investigated using a TiO2/dye/Pt structure with triethanolamine as the sacrificial reagent. The dye-loaded TiO2 photocatalyst exhibited a high yield of hydrogen production when the length of the alkoxy chain was long enough to sufficiently improve the hydrophobicity at the interface between the dye-loaded TiO2 and the water medium. In the alkoxyphenyl-substituted carbazole dyes, the dye with the longest alkoxy chain (C22) exhibited the best hydrogen production performance, but it had a yield only slightly better than that of the dye with the second longest chain length (C16). The dye C22 displayed a turnover number (TON) of 3094 after 24 h of visible light irradiation (>420 nm). However, the compound with no hydrophobic substituent (C1), exhibited the lowest hydrogen production performance with a TON of 1497. Thus, a 207% increase in the hydrogen production yield was observed when hydrophobic substituents were present. Analysis of time-resolved absorption spectra, impedance spectra and incident photon conversion efficiency spectra revealed that the alkoxy chain has a hydrophobic effect at the interface between the dye-loaded TiO2 and the water. Specifically, the hydrophobicity of the dye improved the charge-recombination lifetime for electron injection from the dye into the TiO2 surface in the water for hydrogen production.