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Energy-Level Graded Al-doped ZnO Protection Layer for Copper Nanowire-Based Window Electrodes for Efficient Flexible Perovskite Solar Cells
摘要： Flexible perovskite solar cells (PSCs) have attracted significant interest as promising candidates for portable and wearable devices. Copper nanowires (CuNWs) are promising candidates for transparent conductive electrodes for flexible PSCs because of their excellent conductivity, flexibility, and cost-effectiveness. However, because of the thermal/chemical instability of CuNWs, they require a protective layer for application in PSCs. Previous PSCs with CuNW-based electrodes generally exhibited poor performances compared with their indium tin oxide (ITO)-based counterparts due to the neglect of the interfacial energetics between electron transport layer (ETL) and CuNWs. Herein, an Al-doped ZnO (AZO) protective layer fabricated using atomic layer deposition (ALD) is introduced. The AZO/CuNW-based composite electrode exhibits improved thermal/chemical stability and favorable band alignment between the ETL and CuNWs, based on the Al dopant concentration tuning. As a result, the Al content gradient AZO (g-AZO), composed of three successively deposited AZO layers, leads to highly efficient flexible PSCs with a power conversion efficiency (PCE) of 14.18%, whereas the PCE of PSCs with non-gradient AZO layer is 12.34%. This improvement can be attributed to the efficient electron extraction and reduced charge recombination. Furthermore, flexible PSCs based on g-AZO-based composite electrodes retain their initial PCE, even after 600 bending cycles, demonstrating excellent mechanical stability.
关键词： copper nanowire,flexible perovskite solar cell,transparent bottom electrode,energy level alignment,atomic layer deposition
更新于2025-09-19 17:13:59
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Effects of interfacial energy level alignment on carrier dynamics and photovoltaic performance of inverted perovskite solar cells
摘要： Metal doping is an efficient method for optimizing NiOx as hole transport material in the inverted perovskite solar cells, which can contribute to the optimization of the interfacial energy level alignment, while the underlying influencing mechanism on the charge carrier dynamics and device performance needs to be further elucidated. In this work, NiOx films with modulated energy levels are obtained via Li doping and examined by ultraviolet photoelectron spectrometer. The effects of the energy level alignment of NiOx on the carrier transfer and recombination dynamics are elucidated by transient photovoltage/photocurrent and transient fluorescence dynamics. The Li doping can significantly shift the valence band of NiOx downward, and the 4% Li content endows NiOx with the optimal energy level matching with perovskite and the best charge separation/transfer ability, which can be confirmed through the photoluminescence results. The corresponding device possesses superior photovoltaic parameters with the champion power conversion efficiency of 17.34%, 37% higher than device based on pure NiOx. The results highlight that proper metal doping can optimize the energy level of the hole transport material to well match the perovskite, thus efficiently promoting charge separation and inhibiting charge recombination, which leads to the enhancement of the device performances.
关键词： Li-doped NiOx,Inverted perovskite solar cell,Charge transport/recombination dynamics,Energy level alignment
更新于2025-09-19 17:13:59
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Interfacial Energy Level Tuning for Efficient and Thermostable CsPbI <sub/>2</sub> Br Perovskite Solar Cells
摘要： Inorganic mixed-halide CsPbX3-based perovskite solar cells (PeSCs) are emerging as one of the most promising types of PeSCs on account of their thermostability compared to organic–inorganic hybrid counterparts. However, dissatisfactory device performance and high processing temperature impede their development for viable applications. Herein, a facile route is presented for tuning the energy levels and electrical properties of sol–gel-derived ZnO electron transport material (ETM) via the doping of a classical alkali metal carbonate Cs2CO3. Compared to bare ZnO, Cs2CO3-doped ZnO possesses more favorable interface energetics in contact with the CsPbI2Br perovskite layer, which can reduce the ohmic loss to a negligible level. The optimized PeSCs achieve an improved open-circuit voltage of 1.28 V, together with an increase in fill factor and short-circuit current. The optimized power conversion efficiencies of 16.42% and 14.82% are realized on rigid glass substrate and flexible plastic substrate, respectively. A high thermostability can be simultaneously obtained via defect passivation at the Cs2CO3-doped ZnO/CsPbI2Br interface, and 81% of the initial efficiency is retained after aging for 200 h at 85 °C.
关键词： energy level alignment,flexible perovskite solar cells,thermal stability,all-inorganic perovskite solar cells
更新于2025-09-19 17:13:59
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Energy level alignment and nanoscale investigation of a-TiO <sub/>2</sub> /Cu-Zn-Sn-S interface for alternative electron transport layer in earth abundant Cu-Zn-Sn-S solar cells
摘要： Efficiency of earth abundant and pure sulfide kesterite Cu-Zn-Sn-S (CZTS) solar cell has been stagnant around 9.4% for years, while its counterpart Cu-In-Ga-Se (CIGS) reports an efficiency of more than 22%. Low open circuit voltage (VOC) is the major challenging factor for low efficiency due to severe nonradiative interface recombinations. The existence of higher defect states at the conventional CZTS-CdS interface due to undesirable energy level alignment and lattice misfit promotes trap-assisted recombinations and results in low VOC. In this work, amorphous TiO2 (Eg = 3.8 eV) is proposed as a promising substitute to the conventional and low bandgap CdS (Eg = 2.4 eV) layer. The surface and interface of the CZTS-TiO2 layer were investigated using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The result reveals favorable "spike"-like conformations at the CZTS-TiO2 interface with a conduction band offset value of 0.17 eV. The nanoscale probing of the interface by Kelvin probe force microscopy across CZTS-TiO2 layers shows a higher potential barrier for interface recombination at CZTS-TiO2 in contrast to the conventional CZTS-CdS interface. Finally, the fast decay response and lower persistent photoconductivity of photogenerated carriers for CZTS-TiO2 heterojunction based photodetectors further validate our results. The energy level alignment and nanoscale interface studies signify TiO2 as a promising alternate buffer layer for earth abundant CZTS solar cells.
关键词： XPS,TiO2,CZTS,CdS,energy level alignment,KPFM,UPS,solar cells,interface recombination
更新于2025-09-16 10:30:52
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Synergistic Interface Energy Band Alignment Optimization and Defect Passivation toward Efficient and Simplea??Structured Perovskite Solar Cell
摘要： Efficient electron transport layer–free perovskite solar cells (ETL-free PSCs) with cost-effective and simplified design can greatly promote the large area flexible application of PSCs. However, the absence of ETL usually leads to the mismatched indium tin oxide (ITO)/perovskite interface energy levels, which limits charge transfer and collection, and results in severe energy loss and poor device performance. To address this, a polar nonconjugated small-molecule modifier is introduced to lower the work function of ITO and optimize interface energy level alignment by virtue of an inherent dipole, as verified by photoemission spectroscopy and Kelvin probe force microscopy measurements. The resultant barrier-free ITO/perovskite contact favors efficient charge transfer and suppresses nonradiative recombination, endowing the device with enhanced open circuit voltage, short circuit current density, and fill factor, simultaneously. Accordingly, power conversion efficiency increases greatly from 12.81% to a record breaking 20.55%, comparable to state-of-the-art PSCs with a sophisticated ETL. Also, the stability is enhanced with decreased hysteresis effect due to interface defect passivation and inhibited interface charge accumulation. This work facilitates the further development of highly efficient, flexible, and recyclable ETL-free PSCs with simplified design and low cost by interface electronic structure engineering through facile electrode modification.
关键词： perovskite solar cells,energy level alignment,work function,nonconjugated small molecules,electron transport layers
更新于2025-09-16 10:30:52
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Vacancy defect modulation in hot-casted NiO film for efficient inverted planar perovskite solar cell
摘要： Nickel oxide (NiOx) has exhibited great potential as an inorganic hole transport layer (HTL) in perovskite solar cells (PSCs) due to its wide optical bandgap and superior stability. In this study, we have modulated the Ni2+ vacancies in NiOx film by controlling deposition temperature in a hot-casting process, resulting the change of coordination structure and charge state of NiOx. Moreover, the change of the HOMO level of NiOx makes it more compatible with perovskite to decrease energy losses and enhance hole carrier injection efficiency. Besides, the defect modulation in the electronic structure of NiOx is beneficial for increasing the electrical conductivity and mobility, which are considered to achieve the balance of charge carrier transport and avoid charge accumulation at the interface between the perovskite and HTL effectively. Both experimental analyses and theoretical calculations reveal the increase of nickel vacancy defects change the electronic structure of NiOx by increasing the ratio of Ni3+/Ni2+ and improving the p-type characteristics. Accordingly, an optimal deposition temperature of the NiOx film at 120 °C enabled a 36.24% improvement in the power conversion efficiency compared to that deposited at room temperature (25 °C). Therefore, this work provides a facile method to manipulate the electronic structure of NiOx to improve the charge carrier transport and photovoltaic performance of related PSCs.
关键词： Electronic structure,Vacancy,Hole transport layer,Conductivity,Energy level,Mobility
更新于2025-09-16 10:30:52
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Interfacial charge dynamics of cross-linked polyethylene/ethylene-propylene-diene dual dielectric polymer as revealed by energy band structure
摘要： The discontinuous charge relaxation time related to the electrical conductivity and permittivity, i.e., traditional Maxwell-Wagner relaxation, is the prevailing explanation for the interfacial charge behavior in multi-layered dielectrics. However, the unipolar/bipolar charge dynamics and the corresponding mechanisms from a microscopic viewpoint remain unclear. This work focuses on the dynamics of the interfacial charges in cross-linked polyethylene (XLPE)/ethylene-propylene-diene (EPDM) dual layers to reveal the interfacial charge mechanisms using the energy band structure. The interfacial charge accumulation behavior of the XLPE/EPDM dual- layered structures is clearly observed under electrical stress. Either unipolar or bipolar charges occur at the interface, accompanied by charge injection, and trapping then occurs. The positive charges prefer to accumulate and migrate on the XLPE side. The homo-charges at the interface always remain on the EPDM side. The number of negative charges is higher than the number of positive charges at the interface. The bipolar interfacial charges are ascribed to the charge transfer process that occurs at the interface because of the energy level alignment that is revealed by the electronic energy structures of XLPE and EPDM. The trapping sites, along with the charge injection and transport, contribute to the interfacial charge behavior.
关键词： energy level,interface,trapping site,space charge,energy band structure
更新于2025-09-12 10:27:22
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Mechanism of Organic Solar Cell Performance Degradation upon Thermal Annealing of MoO <sub/>x</sub>
摘要： In this work we focus on P3HT:PC61BM bulk heterojunction (BHJ) devices with MoO3 at the hole extraction side of the BHJ which relies on the formation of a strong dipole at the BHJ/MoO3 interface, as a reference system that has been extensively studied. We have observed depending on when the annealing is performed during device fabrication, device performance either increased or decreased due to formation of a sharp or relatively diffuse interface respectively due to diffusion of MoOx into the BHJ. The measured strength of the dipole at this interface following thermal annealing correlated well with the width of the interface and device performance, with the sharper interface resulting in a stronger dipole and in improved device performance. This is expected to be a general phenomenon for evaporated coatings onto polymeric BHJ, regardless of the polymers involved.
关键词： Organic solar cell,Interface dipole,MoO3,Thermal annealing,Energy level alignment
更新于2025-09-12 10:27:22
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Research progress and design strategy of hole transport materials for perovskite solar cells
摘要： In this paper, the hole transport layer in perovskite solar cells is divided into inorganic materials, organic small molecular materials and polymer materials, and their development in recent years is reviewed. After focusing on the factors affecting the transport ability of the hole transport layer, it was found that the thiophene structure and the triphenylamine group can significantly improve the hole transporting ability of the hole transporting material, thereby designing two novel hole transporting materials TTT and TST. According to the simulation calculation of density functional theory, the energy level prediction of TTT and TST shows that the HOMO energy level can reach -5.27eV and -5.33eV respectively, which can achieve better energy level matching.
关键词： energy level matching,perovskite solar cells,thiophene structure,hole transport materials,triphenylamine group
更新于2025-09-12 10:27:22
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The Theoretical Calculation and Influencing Factors of Yb<sup>3+ </sup>Doped Double-Clad Fiber Laser
摘要： The energy level structure of Yb3+ is analyzed, and a theoretical model is established. The influence of pumping power, fiber length, reflectance of cavity mirror and other related parameters on the performance of the laser is analyzed. The maximum output power can be achieved at a certain reflectance. The higher the input pump power, the smaller the reflectance of the rear mirror which obtains the maximum output power. For different pumping wavelengths, the optimal length of the gain fiber is not the same, and it is also different from the optimal length determined by the minimum pumping threshold. Therefore, in the design of fiber lasers, we should consider comprehensively to determine the appropriate fiber length. Reducing inner raduis is beneficial to improving slope efficiency when the characteristics of the fiber itself remain unchanged.
关键词： Energy Level Structure,Yb3+doped,Fiber Laser,Double-clad Fiber
更新于2025-09-12 10:27:22