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Device characteristics of organic solar cells with the structure ITO/MoO x /active layer/porphyrin/Al. Data based on 48 cells of each type
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We report on large work function shifts induced by the coverage of several organic semiconducting (OSC) films commonly used in organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs) with a porphyrin aggregated layer. The insertion between the organic film and the aluminum cathode of an aggregated layer based on the meso-tetrakis(1-m...
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We have systematically studied interface structure formed by vapor-phase deposition of typical transition metal oxide MoO3 on organic semiconductors. Eight organic hole transport materials have been used in this study. Ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy are used to measure the evolution of the physical, chem...
Citations
... Also, they can be easily modified to possess excellent charge transport characteristics, rendering them valuable as ETLs in OLEDs [19,20]. Our group has previously investigated a variety of porphyrin molecules processed from water solutions to form ETLs in OLEDs with a conventional architecture (that is HTL/EML/ETL) [21]. In this work, we aim to combine the superior properties of porphyrin compounds with the ability of amine groups to reduce the electron injection barrier and prepare a Zn-porphyrin complex with an amidine group (termed as ZnP-amidine) to serve as an ETL material in OLEDs. ...
Charge injection and transport interlayers based on artificial green carbon materials are imperative for a sustainable future of many classes of optoelectronic devices, including organic light-emitting diodes (OLEDs). Especially, porphyrin derivatives can act as efficient energy and charge funnels mimicking their successful photosynthetic function. Here, we report on the application of a novel green carbon material, in particular, a zinc porphyrin derivative bearing an amidine functional group (referred to as ZnP-amidine), as an electron transport material in fluorescent OLEDs based on a green-yellow co-polymer emitter. ZnP-amidine is processed from environmental friendly solvents without any annealing requirements thus being suitable for low-cost sustainable optoelectronics. It is applies as an ultra-thin interlayer between the aluminum cathode and the emissive layer to enable efficient electron transport and stable performance. This work paves the path towards low-cost green carbon materials inspired by natural processes for organic optoelectronics.
... XRD data obtained for two samples prepared by S-C (with layer thickness 155 nm, black line) and DC (250 nm, red line) methods are shown in Fig. 5. Peaks presented in Fig. 5 are related to the ITO crystal layer. According to Ref. 16, F8BT crystal phase has a peak at 5.4 in the XRD pattern. Therefore, the range between 3 and 8 was additionally analyzed. ...
Photoelectric properties of the F8BT polymer are investigated by the Constant photocurrent method (CPM) based on the photocurrent spectra Δjph(hν) and absorption spectra αCPM(hν). The negligibly weak dependence of charge carriers lifetime on the photon energy is found for hν = 2.2–2.7 eV. The peculiarities of the absorption spectra and the photoconductivity spectra are revealed to be determined mainly by the Gaussian distribution of the density of states (DOS). The density of trap states in the F8BT polymer thin films in the exponential DOS is estimated to be 103 times higher than in the Gaussian DOS.
... Electron transfer processes play a vital role in photocatalytic performance. Thus, the delocalized π-conjugated structures of porphyrin aggregates have been employed to investigate photo-induced charge generation and charge recombination (Vasilopoulou et al., 2014). Porphyrin nanostructures with well-defined structures in an ordered arrangement can significantly improve photon harvesting and stability performance of photocatalysts. ...
Functionally designed structures mimicking natural mechanisms can be obtained via supramolecular self-assembly of porphyrin derivatives. Porphyrin-based nanomaterials obtained via self-assembly can be utilized in several applications, such as optical energy or information storage, solar energy conversion, sensors, nanocatalysts, photoelectronics, and photodynamic therapy. In recent years, the fabrication of porphyrin nanostructures via self-assembly for sensing and environmental remediation has attracted extensive interest from scientists, making it an essential aspect of the research field. This review outlines the recent progress in the fabrication of porphyrin-based nanomaterials via self-assembly, their properties, and their applications in environmental treatment and sensing. It begins with introducing porphyrin and the self-assembly method to fabricate porphyrin nanomaterials. Porphyrin nanostructures can be fabricated via self-assembly, including the re-precipitation, coordination polymerization, ionic self-assembly, and other methods, are discussed. Finally, possible applications of porphyrin-based nanomaterials focusing on environmental remediation, sensing, hydrogen production, targeted and imaging therapy, and CO2 reduction are presented with highlights from recent studies in this field.
... The interplanar distance for out-of-plane arrangement increases from 15.04 Å in ZnTCB 4 PP to 19.15 Å in ZnTCO 4 PP, as seen in Table S1. This sharp Bragg peak is consistent with previously reported work on similar molecules [46,47]. The absence of peak at 2θ = 5.5 • , in the case of ZnTCEH 4 PP, suggests a lack of out-of-plane crystalline arrangement of molecules, perhaps caused by the cis-trans branching in the peripheral alkyl chain [48]. ...
The study of excited-state energy diffusion has had an important impact in the development and optimization of organic electronics. For instance, optimizing excited-state energy migration in the photoactive layer in an organic solar cell device has been shown to yield efficient solar energy conversion. Despite the crucial role that energy migration plays in molecular electronic device physics, there is still a great deal to be explored to establish how molecular orientation impacts energy diffusion mechanisms. In this work, we have synthesized a new library of solution-processable, Zn (alkoxycarbonyl)phenylporphyrins containing butyl (ZnTCB4PP), hexyl (ZnTCH4PP), 2-ethylhexyl (ZnTCEH4PP), and octyl (ZnTCO4PP) alkoxycarbonyl groups. We establish that, by varying the length of the peripheral alkyl chains on the metalloporphyrin macrocycle, preferential orientation and molecular self-assembly is observed in solution-processed thin films. The resultant arrangement of molecules consequently affects the electronic and photophysical characteristics of the metalloporphyrin thin films. The various molecular arrangements in the porphyrin thin films and their resultant impact were determined using UV-Vis absorption spectroscopy, steady-state and time-resolved fluorescence emission lifetimes, and X-ray diffraction in thin films. The films were doped with C60 quencher molecules and the change in fluorescence was measured to derive a relative quenching efficiency. Using emission decay, relative quenching efficiency, and dopant volume fraction as input, insights on exciton diffusion coefficient and exciton diffusion lengths were obtained from a Monte Carlo simulation. The octyl derivative (ZnTCO4PP) showed the strongest relative fluorescence quenching and, therefore, the highest exciton diffusion coefficient (5.29 × 10−3 cm2 s−1) and longest exciton diffusion length (~81 nm). The octyl derivative also showed the strongest out-of-plane stacking among the metalloporphyrins studied. This work demonstrates how molecular self-assembly can be used to modulate and direct exciton diffusion in solution-processable metalloporphyrin thin films engineered for optoelectronic and photonic applications.
... Porphyrins have also been used as efficient ETLs in both high-performance OSCs and PeSCs. The ability of porphyrins to self-assemble and to form organized structures was successfully applied in OSCs by Vasilopoulou et al [227]. One metal-free and one metallated porphyrin were inserted between the organic photoactive layer based on P3HT:PC 61 BM and the metal cathode in OSCs. ...
Organic and perovskite solar cells have recently emerged as promising candidates for next-generation solar energy technologies due to their low-cost solution-based fabrication over large areas even on flexible substrates, while offering the possibility of on-chip integration and patterning for custom-designed applications. A key concern over these emerging technologies is their poor operational stability. In a typical device architecture, the organic or perovskite absorber is usually inserted between an electron and a hole transport (extraction) layer in order to match the energetic differences present at the heterointerfaces with the respective contacts. As these layers considerably influence the device performance and operational stability, they have witnessed intense research efforts in recent years resulting in the development of novel materials. Conductive or insulating polymers, non-polymer molecular materials and transition metal oxides are among the most studied classes of interfacial materials. In this review article, we focus on the application of molecular materials, but excluding polymers, either organic or inorganic, to engineer the interfaces in these devices due to their ease of synthesis and facile functionalization of their structure to meet the requirements for successful device modification. We also include ionic compounds of well-defined stoichiometry such as CuSCN, ionic liquids and compounds of molecular anions as the polyoxometalates. We provide a comprehensive account of various molecular interlayers for organic and perovskite solar cell devices. We highlight the origin of enhanced performance and device lifetime and provide a detailed outlook for a focused future development of these materials.
... Было показано, что на свойства материалов на основе порфиринов, в частности на скорость передачи энергии между соседними молекулами, значительно влияет структура ансамбля. Формируемые наноструктуры перспективны для использования в качестве материалов для преобразования солнечной энергии в химическую или электрическую, в частности, в фотокаталитических устройствах, датчиках и органических фотоэлектрических элементах [16][17][18][19][20][21][22][23][24]. Особый интерес представляют ансамбли, структурными и функциональными элементами которых являются стабильные двумерные и трехмерные наночастицы (в том числе, супермолекулы). ...
Contents of the Chapter 18:
Introduction.
18.1. Nanostructuring of macroheterocyclic compounds
18.1.1. Nanostructures based on macroheterocyclic compounds of
the porphyrin type
18.1.2. Langmuir-Blodgett technology – a key technology of
nanoarchitectonics of organic materials
18.1.3. Nanoarchitectures in layers on the surface of the water.
Method for determining the quantitative characteristics of the
structure and model of the layer
18.1.3.1. The traditional method of analysis of compression
isotherms of a floating layer
18.1.3.2. Model of a nanostructured layer and a method of
quantitative analysis of isotherms
18.1.3.3. State diagram. Predicting of the results
18.2. Nanostructured layers and Langmuir-Schaefer films of copper
porphyrazine
18.2.1. Obtaining and basic characteristics of two- and three-
dimensional M-nanostructures of copper porphyrazine in layers at
the water-air interface
18.2.2. Nanocrystallization of copper porphyrazine in Langmuir-
Schaefer films. X-ray diffraction studies
18.3. Porphyrin supermolecules and nanomaterials based on them.
Conclusion.
Literature
... 36−38 However, in the field of OLEDs, works on the electron injection capability of porphyrins are limited to that previously reported by our group, which demonstrated that appropriately oriented aggregated nanostructures of the freebase and zinc-metallated meso-tetrakis (1-methylpyridinium-4yl) porphyrin chloride can improve the energy level alignment at the cathode interface, increase electron injection and transport rates, and enhance the efficiency of OLEDs. 39 In the current work, we use four different zinc porphyrin compounds as thin interlayers between the EML and the Al cathode in OLED devices with the conventional configuration. These porphyrins are appropriately functionalized in order to exhibit high molecular dipole moments and controllable assembly configuration compared to the reference compound with no peripheral groups. ...
... For example, in our previous work, we found a stronger electric field interface dipole when molecules adopt the face-on rather than the edge-on orientation. 39 Herein, we propose that the hydrophilic carboxylic acid groups are likely oriented toward the surface of Al, whereas the hydrophobic porphyrin ring is oriented toward F8BT resulting in a higher hydrophilicity of the F8BT/functionalized porphyrin surfaces relative to pristine F8BT and F8BT/ZnTPP ones ( Figure S8 and Table S1). Therefore, mechanisms (ii) and (iii) may act cooperatively and contribute to the observed work function reduction. ...
... 61 However, our previous studies demonstrated that a large vacuum level shift toward lower values occurs upon depositing a thin porphyrin layer on top of F8BT. 39 This should result in a significant lowering of their LUMO relative to that of F8BT and could offer a viable explanation for the exciton quenching occurring at the porphyrin/F8BT interface but further investigation is needed, which, however, is beyond the scope of the present work. Exciton quenching due to direct energy transfer to the porphyrins would not be expected to play a role in the devices as there is a minimal overlap between the emission spectrum of F8BT (530 nm) and the Soret (about 430 nm in the solid state) bands of porphyrins, while their Q-bands have negligible intensity in the solid state. ...
Here, we use a simple and effective method to accomplish energy level alignment and thus electron injection barrier control in organic light emitting diodes (OLEDs) with a conventional architecture based on a green emissive copolymer. In particular, a series of functionalized zinc porphyrin compounds bearing π-delocalized triazine electron withdrawing spacers for efficient intramolecular electron transfer and different terminal groups such as glycine moieties in their peripheral substitutes are employed as thin interlayers at the emissive layer/Al (cathode) interface to realize efficient electron injection/transport. The effects of spatial (i.e., assembly) configuration, molecular dipole moment and type of peripheral group termination on the optical properties and energy level tuning are investigated by steady-state and time-resolved photoluminescence spectroscopy in F8BT/porphyrin films, by photovoltage measurements in OLED devices and by surface work function measurements in Al electrodes modified with the functionalized zinc porphyrins. The performance of OLEDs is significantly improved upon using the functionalized porphyrin interlayers with the recorded luminance of the devices to reach values 1 order of magnitude higher than that of the reference diode without any electron injection/transport interlayer.
... The small peak present in the spectrum of porphyrin-modified metal oxide centered at 1.7 eV corresponds to the highest occupied molecular orbital (HOMO) of porphyrin compound. 60 We next examined the morphology of the perovskite films grown on TiO 2 without and with porphyrin modification using both SEM and AFM, respectively (see Figure 2a,c and Figures S5−S7). The analysis of the measurement results showed that the porphyrin modification induces more homogeneous perovskite films in both height and spatial aspects. ...
Motivated by the excellent electron transfer capability of porphyrin molecules in natural photosynthesis, we introduce here the first application of a porphyrin compound to improve the performance of planar perovskite solar cells. The insertion of a thin layer consisting of a triazine-substituted Zn porphyrin between the TiO2 electron transport layer and the CH3NH3PbI3 perovskite film significantly augmented electron transfer towards TiO2 while also sufficiently improved the morphology of the perovskite film. The devices employing porphyrin-modified TiO2 exhibited a significant increase in the short-circuit current densities and a small increase in the fill factor. As a result, they delivered a maximum power conversion efficiency (PCE) of 16.87% (average 14.33%) which represents a 12% enhancement compared to 15.01% (average 12.53%) of the reference cell. Moreover, the porphyrin-modified cells exhibited improved hysteretic behaviour and a higher stabilized power output of 14.40% compared to 10.70% of the reference devices. Importantly, non-encapsulated perovskite solar cells embedding a thin porphyrin interlayer showed an elongated lifetime retaining 86% of the initial PCE after 200 hours while the reference devices exhibited higher efficiency loss due to faster decomposition of CH3NH3PbI3 to PbI2.
... 22 Metallated porphyrins represent a widely investigated class of macrocyclic coordination compounds with applications in multidisciplinary fields. [23][24][25][26] They exhibit strong absorption in the visible spectral region and near-infrared, 27,28 while ordered aggregates consisting of self-assembled porphyrin molecules may enable ultra fast energy and electron transfer due to delocalized excited states present in the aggregates as compared to the localized π-π * transitions within the monomer. 29 Functionalized porphyrin compounds have been widely used as light harvesting elements in dye-sensitized solar cells (DSSCs), 30,31 and OSCs, 32 while they have also recently emerged as hole transport layers in perovskite solar cells (PSCs). ...
In the present work, we effectively modify the TiO2 electron transport layer of organic solar cells with an inverted architecture by using appropriately engineered porphyrin molecules. The results show that the optimized porphyrin modifier bearing two carboxylic acids as the anchoring groups and a triazine electron-withdrawing spacer significantly reduces the work function of TiO2 thereby reducing the electron extraction barrier. Moreover, the lower surface energy of the porphyrin-modified substrate results in better physical compatibility between the latter and the photoactive blend. Upon employing porphyrin-modified TiO2 electron transport layers in PTB7:PC71BM-based organic solar cells we obtained an improved average power conversion efficiency up to 8.73%. Importantly, porphyrin modification significantly increased the lifetime of the devices which retained 80% of their initial efficiency after 500 h of storage in the dark. Due to its simplicity and efficacy, this approach should give tantalizing glimpses and generate an impact into the potential of porphyrins to facilitate electron transfer in organic solar cells and related devices.
... OPV technology has attracted significant interest because of their many advantages such as their compatibility with low cost roll-to-roll [3] or lithography-based [4] manufacturing processes and their easy and low cost fabrication [5][6][7]. Currently, the critical challenge for OPVs is to extend their long term stability combined with a high power conversion efficiency (PCE) of 15% , a goal that has been recently approached by employing novel conjugated copolymers with improved optoelectronics properties, non-fullerene acceptors and more sophisticated tandem structures enabled by intelligent interfacial engineering and passivation [8][9][10][11][12][13][14][15][16][17][18][19][20]. Highly efficient organic solar cells utilize a solution-processed bulk-heterojunction (BHJ) structure, in which polymeric donor and fullerene acceptor molecules form nanoscale interpenetrating hole and electron transporting networks, respectively [5][6][7]. ...
In this contribution, we investigate the optoelectronic properties of a donor-acceptor poly(N-Dodecyl-2,7-carbazole-alt-benzothiadiazole (CBZ-BT) copolymer in solutions and thin films, by a combination of complementary optical and electronic spectroscopy techniques including stationary absorption and fluorescence, femtosecond time-resolved and ultraviolet/x-ray photoelectron spectroscopy. Absorption spectroscopy revealed two bands at 322/338 and 445/475 nm for CBZ-BT in solutions/films attributed to the carbazole and benzothiadiazole groups respectively. Photoexcitation either to the absorption band of the carbazole or benzothiadiazole group led to a broad and structureless fluorescence spectrum due to large torsional disorder in the excited state, originating from intramolecular energy transfer between carbazole and benzothiadiazole. Time resolved spectroscopy in solutions reveals a transient red-shift of the emission spectrum within less than 5 ps due to exciton migration and/or conformational relaxation of the polymer backbone. In films, this relaxation is faster accompanied by a quenching of the exciton lifetime. Fluorescence depolarization in solutions follows the rate of spectral relaxation. In films, the overall depolarization is faster leading to a reduced limiting anisotropy, due to efficient energy transfer to adjacent chains with different polarization of the transition dipoles and increased disorder in the solid state. An almost complete quenching of the copolymer fluorescence, taking place on ∼150 fs, was observed upon blending with a fullerene PC70BM acceptor pointing to an efficient electron transfer. CBZ-BT shows a large solid-state ionization potential of 6.2 eV and an electron affinity of 3.7 eV. Its potential as an electron donor in polymer solar cells (PSCs) was unveiled upon fabrication of relatively high open circuit voltage (∼0.85 V) but low power conversion efficiency (∼1.7%) bulk-heterojunction single layer PSCs with PC70BM as electron acceptor.
