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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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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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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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Elucidating the effects of guest-host energy level alignment on charge transport in phosphorescent OLEDs
摘要： The correct choice of guest and host molecules in the light-emitting layer is essential for developing high performance phosphorescent organic light emitting devices. However, the effects of the energy level alignment between the guest and the host are yet to be fully elucidated. In this Letter, we use kinetic Monte Carlo simulations to investigate guest-host systems in which the energy gap of the guest and host is fixed, and only the relative energies of the ionization potential/electron affinity are changed to elucidate their effect on charge transport. It was determined that the mobility balance in the blend was sensitive to the energy level alignment, allowing balanced active layer mobility to be achieved despite the hole and electron mobilities being different by around one order of magnitude. It was also found that the mobility of the faster carrier was more sensitive to the energy level alignment than that of the slower carrier due to reduced slower carrier thermalization under deep charge trapping on the guest.
关键词： guest-host energy level alignment,phosphorescent OLEDs,kinetic Monte Carlo simulations,charge transport
更新于2025-09-12 10:27:22
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Direct Observation of Conductive Polymer Induced Inversion Layer in n‐Si and Correlation to Solar Cell Performance
摘要： Heterojunctions formed by ultrathin conductive polymer [poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)—PEDOT:PSS] films and n-type crystalline silicon are investigated by photoelectron spectroscopy. Large shifts of Si 2p core levels upon PEDOT:PSS deposition provide evidence that a dopant-free p–n junction, i.e., an inversion layer, is formed within Si. Among the investigated PEDOT:PSS formulations, the largest induced band bending within Si (0.71 eV) is found for PH1000 (high PEDOT content) combined with a wetting agent and the solvent additive dimethyl sulfoxide (DMSO). Without DMSO, the induced band bending is reduced, as is also the case with a PEDOT:PSS formulation with higher PSS content. The interfacial energy level alignment correlates well with the characteristics of PEDOT:PSS/n-Si solar cells, where high polymer conductivity and sufficient Si-passivation are also required to achieve high power conversion efficiency.
关键词： core level shifts,band bending,PEDOT:PSS/Si solar cell,energy level alignment,inversion layer
更新于2025-09-11 14:15:04