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Rational Design of Bay-Annulated Indigo (BAI)-Based Oligomers for Bulk Heterojunction Organic Solar Cells: A Density Functional Theory (DFT) Study
摘要： In this paper, we have designed a series of oligomers based on the donor?acceptor concept. Here, acceptor bay-annulated indigo (BAI) dye and donor N-methyl-4,5-diazacarbazole (DAC) are joined by a thiophene linkage. We have substituted the 5th and 5′th positions of the acceptor unit and the 2nd position of the donor unit with various electron-withdrawing and electron-donating groups to study various structural and electronic properties of the compounds. In this regard, we have calculated the dihedral angle, distortion energy, bond length alteration (BLA) parameters, bang gap (ΔH ? L) values, partial density of states (PDOS), electrostatic potential (ESP) surface analysis, reorganization energy, charge transfer rates, hopping mobility values, and absorption spectra of the compounds. The ESP plots of the compounds indicate signi?cant charge separation in the studied compounds. Our study manifests that the designed compounds are prone to facile charge transport.
关键词： charge transport,organic solar cells,donor-acceptor,density functional theory,optoelectronic properties
更新于2025-09-19 17:13:59
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An energy and charge transfer synergetic donora??acceptor heterostructure 2D-COF in photovoltaics
摘要： The formation of orderly p-n heterojunctions by the wafer-scale alignment of donor (D) and acceptor (A) molecules, important to achieve high photocurrent generation in the organic semiconductor-based organization, remains a challenging topic. Presented herein is a distinctive D-A heterostructure two-dimensional organic covalent frameworks (2D-COF) as an efficient organic photovoltaic (OPV) film, supported by the triple roles of the binary building blocks in wafer-scale film growing at water/oil interface, molecular level morphology control, and synergistic F?rest resonance energy transfer (FRET) and charge-transfer (CT) functions. The achieved D-A heterostructure 2D-COF has a wafer-scale size, efficient spectral response, and effective separation of photogenerated electron-hole pairs, resulting in an efficient photocurrent generation which is much larger than those of reported OPV COF materials. Achieved herein confirm that the marriage of FRET and CT synergetic D-A heterostructure and ultrathin 2D-COF film offer unparalleled advantages in OPV.
关键词： Photovoltaics,FRET,Donor-Acceptor heterostructure,Charge-transfer,2D-COF
更新于2025-09-19 17:13:59
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Effect of fused triphenylamine core in star-shaped donor-??-acceptor molecules on their physicochemical properties and performance in bulk heterojunction organic solar cells
摘要： In this work, the synthesis of a novel star-shaped donor-acceptor molecule I with acridine-based core being a fused derivative of triphenylamine linked through π-conjugated terthiophene spacers and terminal hexyldicyanovinyl electron-withdrawing units is reported. Its physicochemical and photovoltaic properties were comprehensively studied and compared to those of molecule II being a structural analog but with a pristine propeller-like triphenylamine core. The novel molecule shows combination of the higher crystallinity, solubility and thermal stability. As compared to II, bulk heterojunction organic solar cells based on I as a donor and PC71BM as an acceptor showed the three times higher hole mobility, 50% larger external quantum efficiency, which resulted in up to twice higher power conversion efficiency reaching 6.14%. This work demonstrates that the triphenylamine core fused by p-tolylmethylene groups in the star-shaped donor acceptor molecules is a promising building block to design highly soluble and crystalline materials for organic optoelectronic devices.
关键词： oligothiophene,organic solar cell,dicyanovinyl,triphenylamine,donor-acceptor molecule
更新于2025-09-19 17:13:59
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Detailed analysis of radiative transitions from defects in n-type monocrystalline silicon using temperature- and light intensity-dependent spectral Photoluminescence
摘要： Sub-bandgap luminescence is characteristic of radiative transitions from defects in semiconductors. However, methods to extract defect-identifying parameters from this luminescence are lacking. Here, we present a method to extract these parameters from temperature- and intensity-dependent micro-photoluminescence (μPL) spectra. The initial “coarse” analysis determines the relevant radiative recombination mechanism by fitting the integrated defect PL spectra with phenomenological models for the temperature- and intensity-dependence. The subsequent “detailed” analysis fits the integrated defect PL spectra using rigorous physical models for the defect radiative recombination and spectral line-shape. Finally, defect parameters are extracted, including the defect energy level(s). As we obtain these values directly from the defect luminescence, our method provides higher confidence than more traditional indirect methods, such as those involving band-to-band PL and photoconductance. We demonstrate our method on spatially non-uniform defects with radiative transitions in n-type monocrystalline silicon samples. It is shown that the defect PL originates from the donor-acceptor pair recombination mechanism, involving a shallow acceptor and deeper donor energy level. The acceptor level is extracted from the temperature-dependent spectra, whilst the intensity-dependent spectra give the sum of acceptor and donor energies.
关键词： Radiative transitions,Silicon,Photoluminescence,Defects,Donor-acceptor pair recombination
更新于2025-09-19 17:13:59
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Role of Emissive and Non‐Emissive Complex Formations in Photoinduced Electron Transfer Reaction of CdTe Quantum Dots
摘要： Bimolecular photoinduced electron transfer (PET) from excited state CdTe quantum dot (QD*) to an electron deficient molecule 2,4-dinitrotoluene (DNT) is studied in toluene. We observed two types of QD-DNT complex formations; (i) non-emissive complex, in which DNT is embedded deep inside the surface polymer layer of QD and (ii) emissive complex, in which DNT molecules are attached to QDs but approach to the QD core is shielded by polymer layer. Because of its non-emissive nature, the lifetime of QD is not affected by dark complex formation, though the steady-state emission is greatly quenched. However, emissive complex formation causes both, lifetime and steady-state emission quenching. In our fitting model, consideration of Poisson distribution of the attached quencher (DNT) molecules at QD surface enables a comprehensive fitting to our time resolved data. QD-DNT complex formation was confirmed by an isothermal titration calorimetry (ITC) study. Fitting to the time resolved data using a stochastic kinetic model shows moderate increase (0.05 ns(cid:2)1 to 0.072 ns(cid:2)1) of intrinsic quenching rate with increasing the QD particle size (from (cid:3) 3.2 nm to (cid:3) 5.2 nm). Our fitting also reveals that the number of DNT molecules attached to a single QD increases from (cid:3) 0.1–0.2 to (cid:3) 1.2–1.7, as the DNT concentration is increased from (cid:3) 1 mm to 17.5 mm. Complex formation at higher quencher concentration assures that the observed PET kinetics is a thermodynamically controlled process where solvent diffusion has no role on it.
关键词： CdTe quantum dot,photo-induced electron transfer,donor-acceptor complex,time-resolved spectroscopy,fluorescence quenching
更新于2025-09-19 17:13:59
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Asymmetric push-pull small molecules with auxiliary electron-accepting unit for bulk heterojunction organic solar cells
摘要： Two small molecular donors (TPA-DPP and TPA-DPP-MDN) were designed with asymmetric push-pull structure, namely, donor-acceptor (D-A) and donor-acceptor-acceptor (D-A-A) systems. They were synthesized and investigated by thermogravimetric analysis, UV–vis spectra, X-ray di?raction, density functional theory (DFT) calculation, electrochemical and the photovoltaic (PV) measurement. The D-A-A architecture (TPA-DPP-MDN) exhibited lower highest occupied molecular orbital (HOMO) of –5.18 eV, narrower optical band gap of 1.52 eV, better thermal stability and higher degree of ordered aggregation than these of the D-A system (TPA-DPP). TPA-DPP-MDN based PV device showed better performance with higher open-circuit voltage (VOC) and short-circuit current density (JSC) than these of TPA-DPP based PV devices due to the low-lying HOMO level and wide spectral absorption range of TPA-DPP-MDN.
关键词： Photovoltaic properties,Small molecular donor,Donor-acceptor-acceptor,Asymmetrical push-pull
更新于2025-09-16 10:30:52
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Dicyanovinylene and Thiazolo[5,4-d]thiazole-Core Containing D-A-D Type Hole Transporting Materials for Spiro-OMeTAD Free Perovskite Solar Cell Applications with Superior Atmospheric Stability
摘要： In perovskite solar cell (PSC) devices, hole transporting materials (HTMs) are vital components affecting the charge separation and play an important role in achieving high efficiencies. These may also protect active light-absorbing layers from degradation. The current best-in-class HTM Spiro-OMeTAD is prohibitively expensive for large scale application and hence design of novel cost-effective HTMs yielding comparable device performance is essential. In this manuscript, we report synthesis of donor-acceptor-donor (D-A-D) type hole transporting materials (TTz-1 and TPDCN) featuring the dicyanovinylene and thiazolo[5,4-d]thiazole cores and evaluate their performance via integrating them in perovskite solar cells (PSCs). The results suggest that both the HTMs are easy to synthesize and demonstrate favourable structural characteristics for device integration. Detailed analysis reveals that the molecules showed appropriate energy level alignment with methylammonium lead iodide (CH3NH3PbI3) perovskite, possess good thermal stability and high hole mobility. Planar PSC devices fabricated using TTz-1 as HTM yielded a power conversion efficiency (PCE) of 11.37%, whilst devices using TPDCN shows a PCE of 10.11%, comparable to PCE of 11.62% obtained in control samples based on Spiro-OMeTAD. In additional, stability analysis of the devices shows that devices fabricated using TTz-1 and TPDCN exhibit superior atmospheric stability as compared to those based on Spiro-OMeTAD. These results suggest that the reported HTM architectures are promising leads for designing new HTMs for perovskite solar cells owing to their simple and scalable synthesis and tunability.
关键词： Thiazolo[5,4-d]thiazole,Hole transporting materials,Dicyanovinylene,Perovskite solar cell,Donor-Acceptor-Donor
更新于2025-09-16 10:30:52
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Synthesis and properties of a novel porphyrin–fullerene triad assembled through donor–acceptor bonding
摘要： Complexation of (hydroxy)(oxo)(5,10,15,20-tetraphenylporphyrinato) molybdenum(v) with 2',5'-di(2-pyridyl)-1'-(3-pyridyl methyl)pyrrolidino[70]fullerene leading to a new donor–acceptor triad is characterized by quantitative description of the equilibrium and the reaction rate. The prospects of the triad as a photosynthetic antenna imitator and an active layer in solar energy conversion devices are substantiated.
关键词： solar energy conversion,porphyrin–fullerene triad,donor–acceptor bonding,photosynthesis
更新于2025-09-16 10:30:52
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Investigation of Photophysical Properties of Ternary Zn–Ga–S Quantum Dots: Band Gap versus Sub-Band-Gap Excitations and Emissions
摘要： Highly luminescent ternary Zn?Ga?S quantum dots (QDs) were synthesized via a noninjection method by varying Zn/Ga ratios. X-ray diffraction and Raman investigations demonstrate composition-dependent changes with multiple phases including ZnGa2S4, ZnS, and Ga2S3 in all samples. Two distinct excitation pathways were identified from absorption and photoluminescence excitation spectra; among them, one is due to the band-gap transition appearing at around 375 and 395 nm, whereas another one observed nearby 505 nm originates from sub-band-gap defect states. Photoluminescence (PL) spectra of these QDs depict multiple emission noticeable at around 410, 435, 461, and 477 nm arising from crystallographic point defects formed within the band gap. The origin of these defects including zinc interstitials (IZn), zinc vacancies (VZn), sulfur interstitials (IS), sulfur vacancies (VS), and gallium vacancies (VGa) has been discussed in detail by proposing an energy-level diagram. Further, the time-dependent PL decay curve strongly suggests that the tail emission (appear around 477 nm) in these ternary QDs arises due to donor?acceptor pair recombination. This study enables us to understand the PL mechanism in new series of Zn?Ga?S ternary QDs and can be useful for the future utilization of these QDs in photovoltaic and display devices.
关键词： photophysical properties,ternary Zn?Ga?S quantum dots,sub-band-gap defect states,donor?acceptor pair recombination,photoluminescence,band-gap transition
更新于2025-09-16 10:30:52
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New cyanopyridine based conjugated polymers carrying auxiliary electron donors: From molecular design to blue emissive PLEDs
摘要： Three new D-A (Donor-Acceptor) configured conjugated polymers, i.e. PPy1-3, centered on strong electron accepting cyanopyridine scaffold carrying varied auxiliary donors, viz. phenylene (PPy1), biphenyl (PPy2), and fluorene (PPy3) were designed and synthesized as blue emitters for PLEDs. The new polymers were subjected to spectral, thermal, photophysical and electrochemical characterization. Also, computational studies (DFT) were performed on the repeating units of polymer using Turbomole 7.2V software package at the B3LYP/TZVP hybrid levels. Further, their weight average molecular masses were found to be 38.8 kDa, 38.9 kDa and 57.7 kDa, respectively as determined by GPC technique. Furthermore, the new polymers PPy1-3, were shown to be stable thermally up to 308-347 ?C. Evidently, they exhibited good photophysical behavior with their optical energy band gaps of 2.53-2.63 eV. Finally, the polymers PPy1-3 were employed as an active emissive layer in standard ITO/PEDOT:PSS/Polymer/Al configured PLEDs. Interestingly, at 12 V all the newly fabricated devices exhibit a stable blue characteristic electroluminescence with low threshold voltages of 3.40-5.20 V, confirming an efficient injection of electrons in the diodes. From the results, it is clear that, the polymers PPy1-3, can be considered as prospective blue light emitters for PLED application.
关键词： Donor-Acceptor,DFT,Cyanopyridine,Electroluminescence,Blue light emitter
更新于2025-09-16 10:30:52