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Origin of Low Open Circuit Voltage in Surfactant-stabilized Organic Nanoparticle-based Solar Cells
摘要： Organic nanoparticle based solar cells have drawn great attention due to its eco-friendly and environ-friendly fabrication procedure. However these surfactant-stabilized nanoparticles suffer open circuit voltage loss due to charge trapping and poor extraction rate at the polymer cathode interface. Here we have investigated origin of voltage loss and charge trapping in surfactant-stabilized nanoparticle based devices. Efficient organic photovoltaic (OPV) devices have been fabricated from an aqueous dispersion of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) nanoparticles stabilized by anionic surfactants. AC impedance spectroscopy has been used to understand the charge transport properties in the dark and in operando conditions. We have demonstrated the similarities in the charge transport properties as well as photocarrier dynamics of the nanoparticle-based OPVs and the bulk hetero-junction OPVs despite fundamental differences in their nanostructure morphology. This study emphasizes the possibility of fabricating highly efficient OPVs from organic nanoparticles by reducing surface defects and excess doping of the polymers.
关键词： Surfactant-Stabilized,Impedance spectroscopy,Organic Photovoltaic,Nanoparticles,Charge Transport
更新于2025-09-19 17:13:59
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A novel cheap, one-step and facile synthesis of hierarchical TiO2 nanotubes as fast electron transport channels for highly efficient dye-sensitized solar cells
摘要： The well-aligned hierarchical TiO2 nanotubes (HTNTs) have been synthesized by a one-step hydrothermal method employing potassium titanium oxalate, ethanol and H2O, which are strongly adhered onto transparent conducting oxide glass. The preparation is straightforward, cheap and applicative for mass manufacture. The thickness of membranes is changed from 12 to 22 lm by adjusting the reaction time. The HTNTs consist of one-dimensional (1D) long TiO2 nanotube trunks and numerous short TiO2 nanorod branches, which can balance surface area and charge transport. By employing optimized HTNTs for dye-sensitized solar cells, a remarkable power conversion ef?ciency of 9.89% is obtained. The result is superior to P25 (8.34%), because 1D trunk-1D branch structure of HTNTs offers the advantages of strong light-harvesting, directed electron transport, and ef?cient charge collection. The HTNTs may ?nd an underlying application in the manufacture of photovoltaic devices.
关键词： Dye-sensitized solar cell,Titania,Hierarchical structure,Charge transport,Nanotube
更新于2025-09-19 17:13:59
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Impact of intentional photo-oxidation of a donor polymer and PC <sub/>70</sub> BM on solar cell performance
摘要： Impact of intentional photo-oxidation of a donor polymer and PC70BM on solar cell performance. A short lifetime is the main factor hindering the wider implementation of low-cost organic photovoltaics through non-ideal encapsulation layers is a known cause of degradation for polymer/fullerene based solar cells. To better understand the origin of this performance degradation, we study the effect of intentional exposure of the photo-active layer to simulated sunlight (AM1.5) in air both on the solar cell performance and on the molecular semiconductor materials. Cathode-free thin films of a blend of the electron donor polymer poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) and the electron acceptor fullerene derivative [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM) were exposed to simulated sunlight in air. Fourier-transform infrared spectra demonstrate the formation of carbonyl photo-oxidation products in the blend films, as well as in the pristine polymer and fullerene films. Solar cells prepared with photo-oxidized active layers show increasingly degraded electrical performance (lower short circuit current, open circuit voltage and fill factor) with increasing exposure time. The increased diode ideality factor indicates that trap-assisted recombination hinders device operation after exposure. The external quantum efficiency decreases drastically with increasing exposure time over the whole photon energy range, while the UV-vis absorption spectra of the blend films only show a mild photo-induced bleaching. This demonstrates that not only the photo-induced degradation of the solar cell performance is not predominantly caused by the loss in light absorption, but charge transport and collection are also hampered. This is explained by the fact that photo-oxidation of PC70BM causes bonds in its conjugated cage to break, as evidenced by the decreased p* intensity in C1s-NEXAFS spectra of PC70BM films. This degradation of unoccupied states of PC70BM will hinder the transport of photo-generated electrons to the electrode. Surface photovoltage spectroscopy gives direct evidence for gap states at the surface of a PC70BM film, formed after 2 hours of exposure and resulting in upward band bending at the PC70BM/air surface. These observations indicate that the photo-oxidation of PC70BM is likely to be the main cause of the performance degradation observed when the photoactive layer of a TQ1:PC70BM solar cell is intentionally exposed to light in air.
关键词： polymer/fullerene solar cells,photo-oxidation,organic photovoltaics,PC70BM,degradation,trap-assisted recombination,charge transport,TQ1
更新于2025-09-19 17:13:59
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Tetraphenylbutadiene-Based Symmetric 3D Hole-Transporting Materials for Perovskite Solar Cells: A Trial Trade-off between Charge Mobility and Film Morphology
摘要： Two three-dimensional symmetric tetraphenylbutadiene derivatives decorated with diphenylamine or triphenylamine fragments are first prepared for use as hole-transporting materials (HTMs) in perovskite solar cells (PSCs). The HTMs are acquired using straightforward synthetic methods and facile purification techniques. The thermal stability, photophysical properties, electrochemical behaviors, computational study, hole mobility, X-ray diffraction, hole transfer dynamics, hydrophobicity, surface morphology, and photovoltaic performances of the HTMs are discussed. The highest power conversion efficiency (PCE) of CJ-04-based cell is 13.75%, which is increased to 20.06% when CJ-03 is used as HTM, superior to the PCE of the cell based on 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) (18.90%). The preparation cost of CJ-03 accounts for merely 23.1% of the price of commercial spiro-OMeTAD, while the concentration of CJ-03 solution used in the device fabrication (60.0 mg mL–1) is lower compared with that of the spiro-OMeTAD solution (72.3 mg mL–1). These results corroborate that the screw-like HTMs with a highly distorted configuration are facilely available and promising candidates for PSCs. More importantly, a practical solution is proposed to achieve moderate charge mobility and good film-formation ability of the HTMs simultaneously.
关键词： butadiene,hole-transporting materials,film morphology,charge transport,perovskite solar cells
更新于2025-09-19 17:13:59
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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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Enhanced Interfacial Binding and Electron Extraction Using Boron‐Doped TiO <sub/>2</sub> for Highly Efficient Hysteresis‐Free Perovskite Solar Cells
摘要： Perovskite solar cells (PSCs) have witnessed astonishing improvement in power conversion efficiency (PCE), more recently, with advances in long-term stability and scalable fabrication. However, the presence of an anomalous hysteresis behavior in the current density–voltage characteristic of these devices remains a key obstacle on the road to commercialization. Herein, sol–gel-processed mesoporous boron-doped TiO2 (B-TiO2) is demonstrated as an improved electron transport layer (ETL) for PSCs for the reduction of hysteresis. The incorporation of boron dopant in TiO2 ETL not only reduces the hysteresis behavior but also improves PCE of the perovskite device. The simultaneous improvements are mainly ascribed to the following two reasons. First, the substitution of under-coordinated titanium atom by boron species effectively passivates oxygen vacancy defects in the TiO2 ETL, leading to increased electron mobility and conductivity, thereby greatly facilitating electron transport. Second, the boron dopant upshifts the conduction band edge of TiO2, resulting in more efficient electron extraction with suppressed charge recombination. Consequently, a methylammonium lead iodide (MAPbI3) photovoltaic device based on B-TiO2 ETL achieves a higher efficiency of 20.51% than the 19.06% of the pure TiO2 ETL based device, and the hysteresis is reduced from 0.13% to 0.01% with the B-TiO2 based device showing negligible hysteresis behavior.
关键词： perovskite solar cells,hysteresis,interfacial binding,charge transport,titanium dioxide
更新于2025-09-19 17:13:59
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Conjugated Polymer Controlled Morphology and Charge Transport of Small-Molecule Organic Semiconductors
摘要： In this study, we report an effective approach to tune the crystallization, microstructure and charge transport of solution-processed organic semiconductors by blending with a conjugated polymer additive poly(3-hexylthiophene) (P3HT). When 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) was used as a model semiconductor material to mix with different amount of P3HT, their intermolecular interactions led to distinctive TIPS pentacene film morphologies, including randomly-oriented crystal ribbons, elongated needles with enhanced long-range order, and grass-like curved microwires with interlinkages. Each type of morphology was found to further correlate to considerably different charge transport and device performance. As compared to pristine TIPS pentacene devices, bottom-gate, top-contact OTFTs with 2% in weight P3HT additive showed a 2-fold and 5-fold improvement of average field-effect mobility and performance consistency (defined as the ratio of average mobility to the standard deviation), respectively. The improvement in transistor electrical performance can be attributed to the combined effect of enhanced crystal orientation and uniformity, as well as increased areal coverage. This work can be applied beyond the particular example demonstrated in this study and to tune the charge transport of other small-molecule organic semiconductors in general.
关键词： OTFTs,TIPS pentacene,organic semiconductors,film morphology,P3HT,charge transport,conjugated polymer
更新于2025-09-19 17:13:59
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Oxychalcogenide Perovskite Solar Cells: A Multiscale Design Approach
摘要： Herein, a multiscale approach is used to design solar cells with oxychalcogenide perovskite absorbers by combining atomistic calculations and macroscale device simulations and optimization. The method involves the computation of charge carrier recombination time as well as the carriers’ scattering time where lattice dynamics and multiple carrier scattering mechanisms are taken into account. Based on microscopically calculated parameters for the oxychalcogenide perovskites, a multiproperty optimization is performed to maximize the power conversion efficiency of the full device. This approach allows identifying optimal designs of some potential oxychalcogenide perovskite solar cells comprehensively. Herein, the methodology opens opportunities to accelerate lab realization and fabrication of solar cells with oxychalcogenide perovskite absorbers. Furthermore, the presented approach combines several general methods, and it should be highly beneficial in saving time and cost of device fabrication and optimization.
关键词： density functional theory,multiscale modeling,photovoltaics,oxychalcogenide perovskites,charge transport
更新于2025-09-19 17:13:59
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Synergistic Effects of Charge Transport Engineering and Passivation Enabling Efficient Inverted Perovskite Quantum-dot Light-emitting Diodes
摘要： All inorganic perovskite quantum dots (QDs) have attracted much attention in the optoelectronic devices due to their fascinating properties such as high photoluminescence quantum yields (PLQYs), narrow emission peak, and facile synthesis process. Herein, we report a synergistic strategy of interfacial engineering and passivation. We construct an inverted device structure with Zinc Magnesium Oxide (Zn0.95Mg0.05O) as electron transport layer and p-n charge generation junction of (N,N’-Bis(naphthalen-1-yl)- N,N’- bis(phenyl) benzidine/ 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile) as hole transport layer to facilitate and balance the charge injection/transport. Meanwhile, a facile post-passivation technique is employed to passivate the cesium lead bromide (CsPbBr3) QDs via supplement of Br anion. The treated QDs exhibit improve PLQY due to decreased surface defect sites and enhanced radiative recombination. As a result, our perovskite quantum dot light-emitting diodes (PVQDLEDs) obtain a maximum luminance of 75792 cd m-2, an extremely low turn-on voltage of 1.9 V, and a maximum external quantum efficiency (EQE) of 5.95%, leading to an increase in EQE by 100% compared with that of the control device. Our work offers an effective approach to improve the performance of PVQDLEDs via multiple effects for the application of displays and solid-state lighting.
关键词： perovskite quantum dots,inverted device structure,passivation,light-emitting diodes,charge transport engineering
更新于2025-09-19 17:13:59
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Interface Engineering by Thiazolium Iodide Passivation Towards Reduced Thermal Diffusion and Performance Improvement in Perovskite Solar Cells
摘要： Interface engineering has become one of the most facile and effective approaches to improve solar cells performance and its long-term stability and to retard unwanted side reactions. Three passivating agents are developed which can functionalize the surface and induce hydrophobicity, by employing substituted thiazolium iodide (TMI) for perovskite solar cells fabrication. The role of TMI interfacial layers in microstructure and electro-optical properties is assessed for structural as well as transient absorption measurements. TMI treatment resulted in VOC and fill factor enhancement by reducing possible recombination paths at the perovskite/hole selective interface and by reducing the shallow as well as deep traps. These in turn allow to achieve higher performance as compared to the pristine surface. Additionally, the TMI passivated perovskite layer considerably reduces CH3NH3 sion and degradation induced by humidity. The un-encapsulated perovskite solar cells employing TMI exhibit a remarkable stability under moisture levels (≈50% RH), retaining ≈95% of the initial photon current efficiency after 800 h of fabrication, paving the way towards a potential scalable endeavor.
关键词： charge transport,opto-electrical properties,perovskites solar cells,passivation,thin film photovoltaics
更新于2025-09-19 17:13:59