Dopamine was introduced for the first time into the perovskite precursor solution to control the perovskite film formation and suppress the formation of ionic defects. The modified devices show ...improved performance (PCE = 21.03%) and stability.
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Perovskite solar cells (PSCs) show great potential for next-generation photovoltaics, due to their excellent optical and electrical properties. However, defects existing inside the perovskite film impair both the performance and stability of the device. Uncoordinated Pb2+, uncoordinated I−, and metallic Pb (Pb0) are the main defects occur during perovskite film preparation and device operation, due to the volatilization of organic cationic components. Passivating these defects is a desirable task, because they are non-radiative recombination centers that cause open-circuit voltage (VOC) loss and degradation of the perovskite layer. Herein, the multifunctional bioactive compound dopamine (DA) is introduced for the first time to control the perovskite film formation and passivate the uncoordinated Pb2+ defects via Lewis acid-base interactions. The Pb0 and I− defects are effectively suppressed by the DA treatment. At the same time, the DA treatment results in a stronger crystal orientation along the (110) plane and upshifts the valence band of perovskite closer to the highest occupied molecular orbital (HOMO) of the hole transport layer (2,2′,7,7′-tetrakis(N,N′-di-pmethoxyphenylamine)-9,9′-spirobifluorene, spiro-OMeTAD), which is beneficial for charge separation and transport processes. Consequently, the stability of MAPbI3 (MA = CH3NH3) PSCs prepared with the DA additive (especially the thermal stability) is effectively improved due to the better crystallinity and lower number of defect trap states of the perovskite film. The optimized MAPbI3 PSCs maintain approximately 90% of their original power conversion efficiency (PCE) upon annealing at 85 °C for 120 h. The best performance triple-cation perovskite (Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3) (FA = formamidinium) solar cell with ITO/SnO2/Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3:DA/spiro-OMeTAD/MoO3/Ag (ITO = indium tin oxide) structure shows a PCE of 21.03% with negligible hysteresis, which is dramatically enhanced compared to that of the control device (18.31%). Therefore, this work presents a simple and effective way to improve the efficiency and stability of PSCs by DA treatment.
The functional group is the main body in modifying the perovskite film, and different functional groups lead to different modification effects. Here, several conjugated triazine-based small molecules ...such as melamine (Cy-NH
), cyanuric acid (Cy-OH), cyanuric fluoride (Cy-F), cyanuric chloride (Cy-Cl), and thiocyanuric acid (Cy-SH) are used to modify perovskite films by mixing in antisolvent. The crystallizations of perovskites are optimized by these molecules, and the perovskite films with low trap density are obtained by forming Lewis adducts with these molecules (Pb
and electron-donating groups including -NH
, C═N-, and C═O; I
and electron-withdrawing groups including F, Cl, N-H, and O-H). Especially for the Cy-F and Cy-Cl, the heterojunction structure is formed in the perovskite layer by p-type modification, which is conducive to charge transfer and collection in PSCs. Compared with that of control devices, the performance of devices with trap passivation and heterojunction engineering is obviously improved from 18.49 to 20.71% for MAPbI
and 19.27 to 21.11% for FA
Cs
PbI
. Notably, the excellent moisture (retaining 67%, RH: 50% for 20 days) and thermal (retaining 64%, 85 °C for 72 h) stability of PSCs are obtained by a kind of second modification (Cy-F/Cy-SH)─spin-coating a few Cy-SH on the Cy-F-modified perovskite film surface. It also reduces Pb pollution because Cy-SH is a highly potent chelating agent. Therefore, this work also provides an effective method to obtain high-performance, stable, and low-lead pollution PSCs, combining trap passivation, heterojunction engineering, and surface treatment.
•Microwave absorbing coefficient is defined, and its expression is derived by electromagnetic theory.•Optimization on the ratio of carbon nanotubes to nickel ferrite is carried out by microwave ...absorbing coefficient with magnetic parameters.•Real part of complex permeability has more obvious effect on absorbing properties than imaginary part.
Based on the physical principle of interaction between electromagnetic field and the electromagnetic medium, the relationship between microwave absorbing coefficient (MAC) and the electromagnetic parameters of materials was established. With the composite materials of nickel ferrite (NiFe2O4), carbon nanotubes (CNTs) and paraffin as an example, optimization on absorbing properties of CNTs/magnetic oxide composite materials was studied at the frequency range of 2–18 GHz, and a conclusion is drawn that the MAC is the biggest at the same frequency, when the CNTs is 10 wt% in the composite materials. Through study on the relationship between complex permeability and MAC, another interesting conclusion is drawn that MAC is obviously affected by the real part of complex permeability, and increasing real part of complex permeability is beneficial for improving absorbing properties. The conclusion of this paper can provide a useful reference for the optimization research on the microwave absorbing properties of CNTs/ferrite composite materials.
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•2D Bi2O2Se nanoflakes are used as electron transport layer (ETL) of perovskite solar cells (PSCs) for the first time.•The PSCs with single 2D Bi2O2Se nanoflakes ETL exhibit the ...higher power conversion efficiency (PCE).•SnO2/2D-Bi2O2Se new hybrid ETL effectively reduce recombination at hetero-interface.•The PCE of PSCs with SnO2/2D Bi2O2Se hybrid ETL is improved to 19.06% from 16.29%.•The stability of PSCs with the novel hybrid ETLs is also improved.
Interfacial engineering has been proved to be an effective way to enhance the performance of perovskite solar cells (PSCs) by reducing interfacial charge recombination. In this work, two-dimensional (2D) Bi2O2Se nanoflakes with high chargemobility are synthesized by facile composited molten salt method, and used as electron transport layer (ETL) of PSCs for the first time. The PSCs based on single 2D Bi2O2Se nanoflakes ETL exhibit power conversion efficiency (PCE) of 9.12%, which is 110% higher than those without ETL (4.32%). To fill pinholes and defects on the surface of SnO2 thin film, we also use the 2D Bi2O2Se nanoflakes to modify the surface of SnO2 thin film, and fabricate SnO2/2D-Bi2O2Se new hybrid ETL to effectively reduce recombination at hetero-interface. Owing to the high charge mobility of 2D Bi2O2Se nanoflakes and cascade band alignment between perovskite active layer and tin dioxide, more efficient electron transport in PSCs is obtained than the single SnO2 ETL. Moreover, novel hybrid ETL provides a smoother and more hydrophobic surface for larger perovskite crystal formation. Compared with PSCs with single SnO2 ETL, the PCE of PSCs based on SnO2/2D Bi2O2Se hybrid ETL is improved to 19.06% from 16.29% with suppressed hysteresis. More interesting, the stability of PSCs with the new hybrid ETLs is also improved due to the improved crystallinity of perovskite active layer. This work shows the 2D Bi2O2Se material has potential for applications in PSCs.
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•A novel ZnO/Ti3C2Tx composite electron transport layer was fabricated.•ZnO/Ti3C2Tx ETL presents high efficiency and excellent stability.•Ti3C2Tx constructs additional charge transfer ...paths in composite ETL.•Ti3C2Tx passivates the surface of ZnO by forming Zn-O-Ti bonding.
MXenes, a novel intriguing family of two-dimensional (2D) transition metal carbides and nitrides, have a wide spectrum of applications owning to their unique optical and electronic properties. Herein, we use Ti3C2Tx, a representative of MXenes, as an additive in zinc oxide (ZnO) to fabricate novel ZnO/Ti3C2Tx nanohybrid composite film. The addition of Ti3C2TX nanosheets constructs new electron transport pathways between the ZnO nanocrystals, and passivates the surface of ZnO by forming the Zn-O-Ti bonding on the ZnO surface. The novel ZnO/Ti3C2Tx nanohybrid film exhibits excellent photoelectric characteristics, and is used as electron transport layers (ETLs) in fullerene and non-fullerene polymer solar cells for the first time. As a result, the power conversion efficiency (PCE) of the photovoltaic devices based on PBDB-T:ITIC with the ZnO/Ti3C2Tx ETLs is 12.20%, up from 10.56% for the corresponding device utilizing pristine ZnO as ETL, a relative increase of 15.53%. Moreover, PM6:Y6 based IPSCs achieve a champion PCE of 16.51% from 14.99% for the reference device, suggesting the good applicability of the ZnO/Ti3C2Tx ETL. The enhancement of PCE is mainly due to the increased transfer and collection of charges in IPSCs. More interestingly, devices based on ZnO/Ti3C2TX composite ETL display relatively good stability compared with the control device. The layered Ti3C2TX should be responsible for such enhancement.
We report a simple synthetic method to prepare amorphous molybdenum oxide (p-MoO
3
) using a favorably stable peroxomolybdic acid organosol as the precursor solution prepared by an ultrasonic ...reaction for the first time. The favorably smooth and dense surface morphology of the p-MoO
3
layers are obtained under 150 °C thermal treatment with good optical properties and a high work function (
W
F
) of 5.26 eV. During the annealing treatment two different oxidation states of Mo ions are observed with increasing the annealing temperature to 150 °C and 200 °C. The best performance of the P3HT:PC
71
BM devices with p-MoO
3
anode buffer layers has been achieved under 150 °C treatment with a power conversion efficiency (PCE) of 4.02%, a
V
OC
of 0.59 V, a
J
SC
of 10.70 mA cm
−2
, and a FF of 63.7%, superior to the corresponding PEDOT:PSS modified devices. Furthermore, the performance of the PTB7:PC
71
BM devices with the annealed p-MoO
3
buffer layers has also been dramatically improved with the best performance parameters of a PCE of 8.46%, a
V
OC
of 0.73, a
J
SC
of 17.02 mA cm
−2
, a FF of 68.1% for 150 °C. The improved performance of the devices originates from the following factors; (i) the favorable and compact surface morphology of the annealed p-MoO
3
films leading to a higher rectification ratio and lower leakage current. (ii) The formation of oxygen vacancies and the growing Mo
5+
cation leading to the change of
W
F
under the annealing treatment. The highest
W
F
of 5.26 eV for 150 °C treatment influences the built-in electric field of the devices with the photocurrent being extracted efficiently at a short-circuit.
We report a simple synthetic method to prepare amorphous molybdenum oxide (p-MoO
3
) using a favorably stable peroxomolybdic acid organosol as the precursor solution prepared by an ultrasonic reaction for the first time.
ZnO surface modified by NAOs to obtain high-efficiency and stable IOSCs by decreasing the WF of ZnO and removing the charge recombination center (–OH) at ZnO surface.
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•ZnO film is ...firstly modified with three environment-friendly natural antioxidants (NAOs).•The modification of NAOs lowers the work function of ZnO surface.•NAOs also effectively passivates the defects of ZnO surface.•Inverted organic solar cells (IOSCs) with new ETLs are firstly fabricated.•The performance of IOSC with ZnO modified by NAOs as ETLs is obviously increased.
Zinc oxide (ZnO) has proved to be an effective electron transport layer (ETL) in organic solar cells (OSCs). However, a variety of defects on ZnO surface and improperly matched work function (WF) greatly restrict the ability of charge transportationinthe OSCs. Surface modification is an effective strategy for solving these problems. In this work, the ZnO film is modified with three environment-friendly natural antioxidants (NAOs): caffeic acid (CA), ferulic acid (FA) and 3, 4-dimethoxy cinnamic acid (DMCA), respectively. The results show that the modification of NAOs not only effectively passivates the defects of ZnO surface, but also lowers the WF of ZnO by forming interface dipoles and upward shift of Fermi level of ZnO. Moreover, the inverted organic solar cells (IOSCs) with ZnO modified by NAOs as ETLs are firstly fabricated. As the result, the IOSC based on PBDB-T: ITIC obtains the increased PCE of 11.75% (ZnO/CA), 11.25% (ZnO/FA) and 10.90% (ZnO/DMCA), which is higher than those of the reference 10.15% (ZnO). Meanwhile, the PCE of IOSC based on PM6:L8-BO with ZnO/CA ETL is also obviously increased from 16.41% to 18.22%. The ambient stability of the IOSCs new ETLs is also significantly improved due to the increased hydrophobicity of ETL and the enhanced crystallinity of active layer. The novel ETLs provide a facile, eco-friendly, low-cost method to realize the efficient and stable photovoltaic devices.
This paper reports the effect on the performance of the solar cells based on poly(3-hexylthiophene) (P3HT):6,6-phenyl C
61-butyric acid methyl ester (PCBM) with different casting solvents. These ...blend films are characterized by UV–vis absorption spectra, photoluminescence spectra, charge-transport dark
J–
V curve, X-ray diffraction pattern curve, and AFM images. The results indicate that high boiling point solvent leads to an enhanced self-organization of P3HT in the active layer, which causes an increased charge transport. Increased incident light absorption and higher carrier mobility in the active layer contribute to the enhancement in the device performance, the power conversion efficiency of 3.69% and fill factor up to 65.3% are achieved with 1,2,4-trichlorobenzene as casting solvent without further heat treatment under Air Mass 1.5, 100
mW/cm
2.
Carrier mobility is a critical factor for power conversion efficiency (PCE) of polymer solar cells (PSCs), and the low charge carrier mobility still limits the performance improvement of PSCs. Adding ...high-mobility material into the active layer is one of the better ways to enhance the PCE of PSCs. Two-dimensional (2D) Bi2O2Se can be an ideal additive material for improving the carrier mobility of PSCs because of its ultrahigh mobility and high thermal stability. In this work, the Bi2O2Se few-layer 2D nanoflakes are fabricated by combining lithium intercalation with shear force-assisted liquid phase exfoliation and applied as an additive to promote charge transport in PSCs for the first time. The 2D Bi2O2Se nanoflakes, when introduced into the active layer, not only provide a new interface between a donor and an acceptor and efficient charge transfer pathways but also induce crystallization of the photosensitive layer and form continuous interpenetrating networks, which promotes the exciton separation and charge transfer in the photosensitive layer. As a result, the PCE of a device based on PBDB-T/ITIC is increased from 10.09% (0 wt %) to 12.22% (2 wt %). Meanwhile, the PCE of a device based on PM6/Y6 is also increased from 14.59% for a binary device to 16.28% for an optimized ternary device (2 wt %). Moreover, the optimized ternary device shows excellent air stability by suppressing the mixing of the two phases. This work provides a good method to enhance the PCE of PSCs and also shows that the Bi2O2Se material has a good prospect in photovoltaic devices.
Graphitic carbon nitride (g-C3N4) has attracted extensive attention in energy storage due to its suitable and tunable bandgap, high chemical/thermal stability, earth abundance and environmental ...friendliness. However, its conductivity should be improved to work as the electrode materials in supercapacitors. In this report, we have prepared a two-dimensional composite (CN-PANI) based on g-C3N4 and polyaniline (PANI) by in-situ polymerization, which can be efficiently applied as electrode material for supercapacitors. The introduction of PANI can increase the conductivity of the electrode, and the porous structure of g-C3N4 can provide enough channels for the transport of electrolyte ions and improve the electrode stability. As a result, the obtained CN-PANI demonstrates excellent specific capacitance (234.0 F g−1 at 5 mV/s), good rate performance and high cycling stability (86.2% after 10,000 cycles at 50 mV/s), showing great potential for high-rate supercapacitors.
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