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Comparison of effects of ZnO and TiO2 compact layer on performance of perovskite solar cells
摘要： In this work, organic?inorganic perovskite solar cells using compact layers of TiO2 and ZnO have been constructed. The ZnO compact layer was synthesized through the chemical hydrolysis process. The TiO2 compact layer was formed by spin-coating C16H28O6Ti in n-butanol. AFM and light absorption studies showed that the surface roughness and optical property of TiO2 and ZnO are nearly identical. However, according to the energy level diagram, the conduction band edge of ZnO is lower than that of TiO2, which is beneficial for electron transfer from the light absorption material to the FTO substrate and thus reducing electron-hole recombination. As a result, employing ZnO in the cell improved both the photocurrent and photovoltaic performance in comparison to TiO2. The best conversion efficiency obtained from the device using ZnO as the compact layer is 17.1%, which is attributed to facilitated photo-generated electron transport in the perovskite solar cell.
关键词： Electronic Transmission,Energy Level.,Compact Layer
更新于2025-09-23 15:19:57
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Variational method of energy level calculation in pyramidal quantum dots
摘要： We suggest a variational method for finding the ground state energy in pyramidal quantum dots. The method is based on using a Gaussian trial wavefunction. We developed an analytical expression for the expectation value of the carrier energy in quantum dots with a constant confining potential (within a single-band model). The problem of finding the ground state energy was reduced to the minimization of an analytical function of three trial function parameters. The proposed variational approach is much faster than the direct approach when solving the three-dimensional Schr?dinger equation, does not demand any special software, and produces quite accurate values of the carrier ground state energy (an error does not exceed 2% of the potential well depth). Generalization of the method to multi-band models, spatially inhomogeneous potentials, effective mass discontinuity, and excited states is discussed. Applicability of the method to different quantum dot systems is considered.
关键词： Gaussian trial wavefunction,single-band model,Schr?dinger equation,variational method,energy level calculation,pyramidal quantum dots
更新于2025-09-23 15:19:57
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Efficient Perovskite Solar Cells by Reducing Interfacea??Mediated Recombination: a Bulky Amine Approach
摘要： The presence of non-radiative recombination at the perovskite surface/interface limits the overall efficiency of perovskite solar cells (PSCs). Surface passivation has been demonstrated as an efficient strategy to suppress such recombination in Si cells. Here, 1-naphthylmethylamine iodide (NMAI) is judiciously selected to passivate the surface of the perovskite film. In contrast to the popular phenylethylammonium iodide, NMAI post-treatment primarily leaves NMAI salt on the surface of the perovskite film. The formed NMAI layer not only efficiently decreases the defect-assisted recombination for chemical passivation, but also retards the charge accumulation of energy level mis-alignment for vacuum level bending and prevents minority carrier recombination due to the charge-blocking effect. Consequently, planar PSCs with high efficiency of 21.04% and improved long-term stability (98.9% of the initial efficiency after 3240 h) are obtained. Moreover, open-circuit voltage as high as 1.20 V is achieved at the absorption threshold of 1.61 eV, which is among the highest reported values in planar PSCs. This work provides new insights into the passivation mechanisms of organic ammonium salts and suggests future guidelines for developing improved passivation layers.
关键词： perovskite solar cells,energy level alignment,1-naphthylmethylamine iodide,non-radiative recombination,chemical passivation
更新于2025-09-23 15:19:57
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Effects of scarring on quantum chaos in disordered quantum wells
摘要： The suppression of chaos in quantum reality is evident in quantum scars, i.e. in enhanced probability densities along classical periodic orbits. They provide opportunities in controlling quantum transport in nanoscale quantum systems. Here, we study energy level statistics of perturbed two-dimensional quantum systems exhibiting recently discovered, strong perturbation-induced quantum scarring. In particular, we focus on the effect of local perturbations and an external magnetic field on both the eigenvalue statistics and scarring. Energy spectra are analyzed to investigate the chaoticity of the quantum system in the context of the Bohigas–Giannoni–Schmidt conjecture. We find that in systems where strong perturbation-induced scars are present, the eigenvalue statistics are mostly mixed, i.e. between Wigner–Dyson and Poisson pictures in random matrix theory. However, we report interesting sensitivity of both the eigenvalue statistics to the perturbation strength, and analyze the physical mechanisms behind this effect.
关键词： quantum well,energy-level statistics,disorder,quantum scar,quantum chaos
更新于2025-09-19 17:15:36
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Introduction of Multifunctional Triphenylamino Derivatives at the Perovskite/HTL Interface to Promote Efficiency and Stability of Perovskite Solar Cells
摘要： Surface passivation is a widely used approach to promote the efficiency and stability of perovskite solar cells (PSCs). In the present project, a series of new organic surface passivation molecules, which contain the same triphenylamino group with the hole transfer material of PSCs has been synthesized. These new passivation molecules are supposed to have both “carrier transfer” capability and “defect passivation” potential. We find that by using N-((4-(N,N,N-triphenyl)phenyl)ethyl)ammonium bromide (TPA-PEABr) as a surface passivation molecule, the efficiency of the PSCs can be improved from 16.69% to 18.15%, mainly due to an increased Voc (1.09 V compared with 1.02 V in control devices). The increased Voc is due to the reduced surface defect density and a better alignment for the related energy levels after introducing the TPA-PEABr molecules. Moreover, the stability of the PSCs can be significantly improved in TPA-PEABr passivated devices due to the hydrophobic nature of TPA-PEABr. Our results successfully demonstrate that passivation of the perovskite surface with a carefully designed multiple functional small organic molecule should be a useful approach for more stable PSCs with high efficiency.
关键词： Stability,Surface passivation,Perovskite solar cell,Triphenylamine derivative,Energy level alignment
更新于2025-09-19 17:13:59
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New xanthone derivatives as host materials: Improvement of carriers balance for high-efficiency green phosphorescent OLEDs using two host materials
摘要： Three new xanthone derivatives, 3-(4-(diphenylamino)-9H-carbazol-9-yl)-9H-xanthen-9-one (XanCarDipha), 2-(4-(4-(diphenylamino)-9H-carbazol-9-yl)phenyl)-9H-xanthen-9-one (p-XanCarDipha), and 2-(3-(4-(diphenylamino)-9H-carbazol-9-yl)phenyl)-9H-xanthen-9-one (m-XanCarDipha) as host materials are designed and synthesized, and they are applied to the development of green phosphorescent organic light-emitting diodes (PHOLEDs). Due to the different connection methods of carbazole units and xanthone units of the compounds, the efficiency curves of XanCarDipha exhibited significantly difference compared to other two materials after above three new materials are made into OLED devices as single host in emitting layer (EML). In EML, a PHOLED using 1: 1 p-XanCarDipha: CarTria as double host and doped with 12 wt% tris(2-phenylpyridine) iridium as a guest material can achieve the uppermost external quantum efficiency (EQE) of 20.93% , the uppermost current efficiency (CE) of 77.40 cd A-1, and the uppermost power efficiency (PE) of 93.15 lm W-1. Compared with corresponding highest luminous efficiency of devices using p-XanCarDipha as single host material (16.86%, 62.55 cd A-1 and 42.60 lm W-1), the efficiency of double-host materials has been significantly enhanced. Meanwhile, the glass transition temperatures (Tg) of the three new host materials are all higher than 120 °C, indicating that they should have good thermal stability in the device application. This work not only provides a design direction for xanthones, but also demonstrates its superior performance on OLED devices when they combined with another host material.
关键词： Double-host materials,Electroluminescent properties,PHOLEDs,Carrier balance,Energy level
更新于2025-09-19 17:13:59
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Bifunctional Ultrathin PCBM Enables Passivated Trap States and Cascaded Energy Level toward Efficient Inverted Perovskite Solar Cells
摘要： Inverted perovskite solar cells (PSCs) with C60 framework are known for their common drawback of low power conversion efficiency (PCE) < 20% because of non-radiative recombination and inefficient charge transport at their perovskite interfaces. Here, we report an ultra-thin [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as a cap layer on perovskite films to overcome this issue. Such a functional cap layer efficiently passivates trap states and establishes a gradient energy level alignment onto perovskite, facilitating the efficient charge transfer and extraction. The as-fabricated inverted PSCs capped with such ultra-thin PCBM exhibit a record PCE of 20.07%. After the storage under N2 atmosphere for more than 500 hours, the PCE of PSCs retains over 85% of its initial level. Our work provides an effective method to upgrade inverted PSCs with the C60 framework with improved efficiency and stability.
关键词： Defect passivation,Cascaded energy level,Interface Engineering,Inverted Perovskite solar cell,Ultra-thin PCBM,High efficiency
更新于2025-09-19 17:13:59
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Interfacial Bridge Using a <i>cis</i> ‐Fulleropyrrolidine for Efficient Planar Perovskite Solar Cells with Enhanced Stability
摘要： Fullerene derivatives, especially after purposely functionalization, have potential to efficiently passivate interfacial defects between perovskites and electron transport layers. In this work, a fullerene derivative with amine functional group, 2,5-diphenyl C60 fulleropyrrolidine (DPC60), is synthesized and employed as an interfacial layer between a perovskite and SnO2 in planar perovskite solar cells (PSCs). The cis-configuration and the specific amine group of DPC60 effectively enhance the chemical interaction between the perovskite and DPC60, promoting the passivation of perovskite defects at the interface. The suitable energy level of DPC60 and the improved conductivity of the SnO2/DPC60 film facilitate the electron extraction from the perovskite layer. As a result, PSCs incorporated with DPC60 reach a PCE of 20.4% with high reproducibility, which is much higher than that of the bare SnO2 based devices (18.8%). Furthermore, the hydrophobic DPC60 layer suppresses heterogeneous nucleation and improves the crystallinity of the perovskite film, resulting in better device stability, retaining 82% of its initial efficiency after 200 h of 1 sun continuous irradiation and thermal ageing (55 ± 5 °C).
关键词： fullerene derivatives,chemical interactions,perovskite solar cells,passivation,energy level alignment
更新于2025-09-19 17:13:59
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Thermal-Annealing Effects on Energy Level Alignment at Organic Heterojunctions and Corresponding Voltage Losses in All-Polymer Solar Cells
摘要： Matched energy level alignment is a key requirement for efficient organic devices such as organic light-emitting diodes, photovoltaics, and field-effect transistors. The effect of thermal stress/annealing on energy level alignment and related properties of the devices are less discussed compared to the extensively explored effect on morphology and corresponding device performance. Here all polymer solar cells (all-PSCs) are employed to study thermal annealing effects on energy level alignment and the corresponding effect on the device properties of the all-PSCs. It is found that optimized energy level alignment can be achieved by thermal annealing. An interface dipole layer at the donor/acceptor interface is introduced by energy level realignment that assists charge generation by reducing geminate recombination so that the voltage loss is dramatically reduced, improving the performance of the all-PSCs.
关键词： Thermal Annealing,Voltage losses,Polymer solar cell,General design rule,Energy level alignment
更新于2025-09-19 17:13:59
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Low Temperaturea??Processed Zr/F Coa??Doped SnO <sub/>2</sub> Electron Transport Layer for Higha??Efficiency Planar Perovskite Solar Cells
摘要： The energy band position and conductivity of electron transport layers (ETLs) are essential factors that restrict the efficiency of planar perovskite solar cells (p-PSCs). Tin oxide (SnO2) has become a primary material in ETLs due to its mild synthesis condition, but its low conduction band position and limited intrinsic carriers are disadvantageous in electron transport. To solve these problems, this work exquisitely designs a Zr/F co-doped SnO2 ETL. The doping of Zr can raise the conduction band of SnO2, which reduces the energy barrier in electron extraction and inhibits the interface recombination between the ETL and perovskite. The open-circuit voltage (VOC) of p-PSCs consequently increases. F? doping belongs to n-type doping. Thus, it equips SnO2 with a large number of free electrons and improves the conductivity of the ETL and short-circuit current (JSC). The device based on Zr/F co-doped ETL achieves a high efficiency of 19.19% and exhibits a reduced hysteresis effect, which is more satisfactory than that of a pristine device (17.35%). Overall, our research successfully adjusts the energy band match and boosts the conductivity of ETL via Zr/F co-doping. The results provide an effective strategy for fabricating high-efficiency p-PSCs.
关键词： electron transport layer,Zr/F co-doping,energy level match,planar perovskite solar cell,tin oxide (SnO2)
更新于2025-09-19 17:13:59