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Energy disorder and energy level alignment between host and dopant in organic semiconductors
摘要： Energy level alignment between host and dopant molecules plays a critical role in exciton formation and harvesting in light emission zone of organic light-emitting diodes. Understanding the mechanism for predicting energy level alignment is thus important in materials selection for fabricating high-performance organic light-emitting devices. Here we show that host-dopant energy level alignment strongly depends on film thickness and substrate work function by using X-ray and ultraviolet photoemission spectroscopy. Invariant Gaussian density of states fails to explain the experimental data. We speculate that energy disorder in molecules next to the surface dictates the alignment. Ultraviolet photoemission spectroscopy measurements of several archetypical organic semiconductors confirm our speculation. An empirical interface disorder function is derived and used to construct a functional Gaussian density of states to compute host energy levels. Host-dopant energy level alignment is then computed by applying the universal energy alignment rule and is found in excellent agreement with the experimental data.
关键词： Host-dopant systems,Organic semiconductors,Energy level alignment,Photoemission spectroscopy,Energy disorder
更新于2025-09-23 15:23:52
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Modification of TiO <sub/>2</sub> (1?1?0)/organic hole transport layer interface energy levels by a dipolar perylene derivative
摘要： Our photoemission study reveals that the work function of TiO2(1 1 0) decreases by up to 1.5 eV upon deposition of 9-(bis-(p-(tert-octyl)phenyl)amino)-perylene-3,4-dicarboxylic anhydride (BOPA-PDCA). This effect is attributed to a chemical reaction of TiO2(1 1 0) and the molecular anhydride group, as well as the molecular dipole. Analysis of the film thickness dependent photoemission and metastable atom electron spectroscopy data reveals that for low coverage the perylene backbone of BOPA-PDCA is almost parallel to the substrate surface and higher coverage leads to an orientational transition to essentially upright standing molecules. Comparing the energy-level alignment between TiO2(1 1 0) and the hole transport materials N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) without and with the BOPA-PDCA interlayer, we find that the perylene derivative has a positive impact on the level alignment for dye-sensitized solar cells with high open-circuit voltages.
关键词： solid state dye-sensitized solar cell,titanium dioxide,energy-level alignment,ultraviolet photoelectron spectroscopy,metastable atom electron spectroscopy,perylene
更新于2025-09-23 15:23:52
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Role of CdSe and CdSe@ZnS quantum dots interlayers conjugated in inverted polymer solar cells
摘要： We demonstrate the use of CdSe quantum dots (QDs) as an interlayer for improving photovoltaic performance in the inverted polymer solar cells (iPSCs). The conjugation of CdSe and CdSe@ZnS core@shell QDs between polyethylenimine ethoxylated (PEIE) polymer and PTB7:PC71BM blended layer played an important role in increasing the short circuit current density by F€orster resonance energy transfer (FRET) and efficient charge transport. The drastic mutual photoluminescence quenching suggests that the photon energy absorbed by PTB7:PC71BM are effectively transferred to the QDs. The PTB7:PC71BM based iPSCs with the CdSe QDs interlayer exhibits higher power conversion efficiency of 8.13%, which is 13.4% higher than that of the control device. The iPSCs with CdSe@ZnS QDs interlayer showed relatively lower PCE of 7.31%, which could be due to an increase in carrier recombination inside QDs by relatively high energy level of ZnS shell. As a consequence, the enhanced photovoltaic performance of iPSCs with CdSe QDs interlayer can be attributed to an effective charge transport and an increase in the overall photocurrent by FRET.
关键词： Carrier transport,Resonance energy transfer,Quantum dots,Inverted polymer solar cells,CdSe,Energy level alignment
更新于2025-09-23 15:21:01
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Highly Efficient and Stable Pure 2D Perovskite Based Solar Cells with 3-Aminopropionitrile Organic Cation
摘要： Pure two-dimensional (2D) perovskite (n = 1) based perovskite solar cells (PSCs) have been proven to have excellent stability against humidity, but the photovoltaic performance is very poor due to the parallel orientation to the substrate and mismatched energy alignment in the PSC device. We report herein a novel bulky organic cation of 3-aminopropionitrile (3-APN) for constructing a pure 2D hybrid lead-iodide perovskite. The crystal structure of (3-APN)2PbI4 features a stable layered and undistorted PbI6 octahedral geometry ( ∠ Pb–I–Pb = 180o) with a small I···I distance (4.66 ?), and the crystals grow in a dominant out-of-plane direction to the substrate. In addition, the existence of intramolecular H-bond between cyano groups and ammonium heads result in an appropriate valence band level of (3-APN)2PbI4 for well-matched energy level alignment in the device, benefitting the interfacial charge transfer and hence better photovoltaic performance. As a result, the PSC with the pure 2D (3-APN)2PbI4 perovskite based PSC achieves power conversion efficiency of 3.39%, which is the highest value thus far for the pure 2D lead?iodide perovskite family, to the best of our knowledge. More importantly, this pure 2D (3-APN)2PbI4 perovskite based PSC demonstrates excellent stability against humidity. This work demonstrates that there is great potential to realize efficient and stable pure 2D perovskite based PSCs through the wise design of organic cations.
关键词： crystal orientation,3-aminopropionitrile,pure 2D,energy level alignment,perovskite solar cells
更新于2025-09-23 15:21:01
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[SpringerBriefs in Applied Sciences and Technology] Air-Stable Inverted Organic Light-Emitting Diodes || Carrier Injection Mechanism
摘要： Both hole and electron injection layers are commonly used in recent OLEDs to reduce the injection barrier between electrodes and organic layers. This injection barrier originates from the energy difference between the work function (WF) of the electrode and the energy level of the organic layer. For instance, the hole injection barrier is defined as the energy difference between the Fermi level of the anode and the highest occupied molecular orbital (HOMO) level of the organic layer on the anode, as shown in Fig. 4.1a. Thus, an ideal hole injection material is the material that can make the surface WF of the anode larger (Fig. 4.1b). On the other hand, an ideal electron injection material is the material that can make the surface WF of the cathode smaller (Fig. 4.1c).
关键词： energy level alignment,OLEDs,electron injection,hole injection,work function
更新于2025-09-23 15:21:01
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RbF modified FTO electrode enable energy-level matching for efficient electron transport layer-free perovskite solar cells
摘要： The development of highly efficient electron transport layer free perovskite solar cells (ETL-free PSCs) with simplified and economical device configurations can significantly motivate the commercialization of PSCs. However, the performance of ETL-free PSCs has been hampered by the sluggish charge extraction and severe charge carrier recombination due to the energy-level mismatch at the interface of the perovskite and the transparent conductive electrode FTO (fluorine doped tin-oxide). In this study, this issue is well solved by modifying the FTO surface with a simple, low-cost and non-toxic rubidium fluoride (RbF) interlayer. An interfacial dipole layer is formed on the FTO surface by inserting a RbF layer, which tunes the work function of FTO, eliminates the electron transport barrier and optimizes the energy-level alignment at the FTO/perovskite interface, thereby enhancing the charge transfer and suppressing the carrier recombination. Consequently, the rigid ETL-free PSCs with RbF layer yield high efficiencies of up to 18.79%, higher than that of ETL-free devices on bare FTO (16.03%). By virtue of the low-temperature processability, a superior PCE of 15.7% has been achieved by flexible ETL-free PSCs fabricated on RbF modified plastic substrate. This study provides a simple, efficient and environmentally friendly approach to modify the FTO electrode for fabricating ETL-free PSCs, which contribute to promote the design of advanced interface materials for simplified and high-performance perovskite photovoltaics.
关键词： ETL-Free Perovskite Solar Cells,Interface Dipole,Energy-Level Matching,Aqueous Processing
更新于2025-09-23 15:21:01
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Ultrathin sheetlike BiOAc0.67I0.33 solid solution with optimal energy levels and enhanced visible-light photocatalytic activity
摘要： BiO(CH3COO)xI1-x (denoted as BiOAcxI1-x) solid solutions were easily synthesized by co-precipitation method. The BiOAcxI1-x solid solutions with x = 0.67 possessed the highest visible-light photocatalytic activity for the degradation of multiple pollutants like rhodamine B (RhB), malachite green (MG) and colorless salicylic acid (SA) due to ultrathin sheetlike structures and optimal energy levels, which could e?ectively impede the re-combination of photogenerated electron-hole pairs. High separation e?ciency of charge carriers was further con?rmed by photoelectrochemical techniques. Various factors to a?ect photocatalytic performance of the BiOAcxI1-x were investigated in detail and the corresponding photocatalytic mechanism was proposed.
关键词： BiOAcI solid solution,Co-precipitation,Photocatalysis,Energy level
更新于2025-09-23 15:21:01
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Engineering of Electron Extraction and Defects Passivation via Anion Doped Conductive Fullerene Derivatives as Interlayers for Efficient Invert Perovskite Solar Cells
摘要： The major limitation of organic-inorganic perovskite solar cells performance is the existence of numerous charged defects at the absorption layer surface, which caused charge carrier recombine depravation. These defects have remarkable influence on the charge extraction, which further caused the instability of device and induce severe hysteresis. Here, three low-cost anion-doping conductive fullerene derivatives, fullerene bis(phenethyl alcohol) malonate (FMPE-I), fullerene bis(ethylenediamine) malonamide (FEDA-I), and fullerene bis(propanediamine) malonamide (FPDA-I), are developed for the first time as interfacial layers between a perovskite and phenyl-C61-butyric acid methyl ester (PCBM) in planar invert perovskite solar cells under mild solution fabrication. The constituent Lewis basic halides and the specific amide groups of conductive fullerene derivatives efficaciously heighten the chemical interaction between the perovskite and conductive fullerene derivatives since the iodide can combine with under-coordinated Pb2+ by electrostatic interaction and amide group can facilely combined with I by hydrogen bonding, improving the dual-passivation of perovskite defects. Moreover, due to the well-matched energy level of conductive fullerene derivatives and the high conductivity of the perovskite/interlayer film, the electron extraction capacity can be effectively enhanced. Consequently, superior optoelectronic properties are achieved with an improved power conversion efficiency of 17.63%, which is considerably higher than that of the bare PCBM based devices (14.96%), for the perovskite device with conductive interlayer treatment along with a negligible hysteresis. Moreover, hydrophobic conductive fullerene derivatives improve the resistance of device to moisture. The conductive fullerene derivative-based devices without encapsulation are maintained at 85% of the pristine power conversion efficiency value after storage in ambient conditions (25 oC temperature, 60% humidity) for 500h.
关键词： dual-passivation,energy level alignment,perovskite solar cells,Conductive fullerene derivatives,interface engineering
更新于2025-09-23 15:21:01
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Reducing photovoltage loss at anode contact of methylammonium-free inverted perovskite solar cells by conjugated polyelectrolyte doping
摘要： The efficiency of perovskite solar cells (PSCs) developed rapidly in recent years, but the stability still lagged behind. Ion migration effect, especially from the small methylammonium (MA) cations, is a main factor for stability issues and MA-free perovskite is one appreciated pathway to suppress ion migration. In this work, we reveal there is a much lower valence band maximum (VBM) of -5.8 eV for the most studied MA-free perovskite of FA0.83Cs0.17PbI2.7Br0.3, which is much different from traditional perovskite and the huge energy level mismatch between perovskite and hole transport layer (HTL) is a main factor to limit the device performance of MA-free PSCs. It is found doping with conjugated polyelectrolyte of poly[(9,9-bis(3’-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN-Br) in perovskite can significantly promote anode contact and result in better device performance as well as stability of FA0.83Cs0.17PbI2.7Br0.3 based MA-free PSCs in inverted planar structure. The PFN-Br arise the energy position of VBM of perovskite and results in well-matched energy levels between perovskite and HTL of poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine (PTAA). Carrier extraction and transportation are highly encouraged at the surface of PTAA / perovskite, and the corresponding interface recombination is effectively suppressed. As a result, a 60mV increased VOC is achieved, which promotes champion device efficiency to 20.32%. At the same time, the efficient device displays a significant stability under continuous illumination and bias at MPP conditions, which could remain 80% of its initial power conversion efficiency (PCE) under continuous operation under one sun illumination over 500 hours.
关键词： PFN-Br doping,MA-free perovskite,device stability,energy level alignment,perovskite solar cells
更新于2025-09-23 15:19:57
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Simultaneous Power Conversion Efficiency and Stability Enhancement of Cs <sub/>2</sub> AgBiBr <sub/>6</sub> Leada??Free Inorganic Perovskite Solar Cell through Adopting a Multifunctional Dye Interlayer
摘要： Perovskite solar cells (PSCs) are highly promising next-generation photovoltaic devices because of the cheap raw materials, ideal band gap of ≈1.5 eV, broad absorption range, and high absorption coefficient. Although lead-based inorganic-organic PSC has achieved the highest power conversion efficiency (PCE) of 25.2%, the toxic nature of lead and poor stability strongly limits the commercialization. Lead-free inorganic PSCs are potential alternatives to toxic and unstable organic-inorganic PSCs. Particularly, double-perovskite Cs2AgBiBr6-based PSC has received interests for its all inorganic and lead-free features. However, the PCE is limited by the inherent and extrinsic defects of Cs2AgBiBr6 films. Herein, an effective and facile strategy is reported for improving the PCE and stability by introducing an N719 dye interlayer, which plays multifunctional roles such as broadening the absorption spectrum, suppressing the charge carrier recombination, accelerating the hole extraction, and constructing an appropriate energy level alignment. Consequently, the optimizing cell delivers an outstanding PCE of 2.84%, much improved as compared with other Cs2AgBiBr6-based PSCs reported so far in the literature. Moreover, the N719 interlayer greatly enhances the stability of PSCs under ambient conditions. This work highlights a useful strategy to boost the PCE and stability of lead-free Cs2AgBiBr6-based PSCs simultaneously, accelerating the commercialization of PSC technology.
关键词： charge carrier separation,dye interlayer,Cs2AgBiBr6,energy level alignment,perovskite solar cell
更新于2025-09-23 15:19:57