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F110146148 Laila- Ultra-thin and high transparent Cu2ZnSnSe4 - NiOx double-layered....pptx
1. ULTRA-THIN AND HIGHTRANSPARENT
CU2ZNSNSE4/NIOX DOUBLE-LAYERED
INORGANIC HOLE-TRANSPORTING LAYER
FOR INVERTED STRUCTURE CH3NH3PBI3
PEROVSKITE SOLAR CELLS
(Journal of Alloys and Compounds,August 2021)
Ching-HoTien, Lung-ChienChen, Kuan-Lin Lee
Reported by: 孫萊拉 (F110146148)
2. Abstract
The double-layered film for hole transporting layer material such as the ultra-thin
sputtered Cu2ZnSnSe4 (CZTSe) combined with solution-processed NiOx film applied in
inverted CH3NH3PbI3 perovskite solar cells gives the beneficial to enhance the hole
extraction and suppress electron transport.
The advantage of this material are for its high transmittance (85%), high hole mobility,
low resistivity, earth-abundant elemental constituents, and non-toxic properties.
On this experiment, the final power coefficient efficiency (PCE) around 13.46% were
achieved. And it improved the stability, of which this device remains 73% of the initial
PCE after 350h in the nitrogen-filled glove box.
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4. Sample Voc (V)
400°C-annealed-CZTSe 0.60
400°C-annealed-CZTSe/NiOx 1.01
500°C-annealed-CZTSe 0.68
500°C-annealed-CZTSe/NiOx 1.01
600°C-annealed-CZTSe 0.70
600°C-annealed-CZTSe/NiOx 1.03
Fig. 2. (a) Energy level alignment of perovskite solar cell with CZTSe/NiOx HTLs, (b) Cross-sectional SEM image
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5. Fig. 3. (a) XRD patterns and (b)-(d) Top view SEM images of the CZTSe films with different annealing temperature.
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6. Fig. 4. Transmission spectra of (a) CZTSe films with different annealing temperature on the glass
substrate and (b) different annealing temperature CZTSe coated on NiOx films.
Highly transparent >85% Decreased 1-3%
500˚-annealed CTZSe
600˚-annealed CTZSe
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7. Fig. 4. (c) Absorbance of MAPbI3 layers deposited on CZTSe/NiOx films with
different annealing temperature of CZTSe.
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9. Fig. 6. Current density-voltage (J–V) curves
for the inverted perovskite solar cells based on
the CZTSe single-layer HTL under different
annealing temperature.
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11. Fig. 8. Stability testing of perovskite solar cells employing
PEDOT:PSS and 600˚C annealed-CZTSe/NiOx HTLs. (a)
actual PCEs, (b) normalized PCE values
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12. Conclusion
The inverted MAPbI3 perovskite solar cells with sputtered CZTSe/solution-processed NiOx
films as a low-cost double-layered inorganic HTL facilitates better charge collection, light
absorption, and transportation compared to the NiOx HTL thus reduced the interface hole
recombination, leading to considerably improvedVoc and FF.
The CZTSe/NiOx double-layer HTL prevents the corrosion of acidic organic HTL on the ITO
electrode, thereby improving the long-term stability of perovskite solar cells
Upon optimizing the annealing temperature of CZTSe film, the 600˚C-annealed CZTSe
films exhibit better crystallinity, high transmittance (>85%), and high hole mobility (15.1
cm2v-1s-1). Compared with single NiOx HTL devices showing PCE of 10.49%
The double-layered CZTSe/NiOx HTLs devices showed a best efficiency of 13.46%, and
retaining 73% of its initial PCE even after storage 350h of testing.
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-The process of the device fabrication started with FTO as the first layer, and followed by CZTSe on the second layer. The substrates were treated with RF (radio frequency) magnetron sputtering process to make ultra thin layer of CZTSe. After RF magnetic sputtering process, the deposited ultra-thin films were annealed with various temperature of 400, 500, and 600 C. Afterwards, the NiOx precursor solution were layered on top of the CZTSe films.
RF (radio frequency) magnetron sputtering is a process that is used to make thin film, especially when using materials that are non-conductive. In this process, a thin film is grown on a substrate that is placed in a vacuum chamber. Powerful magnets are used to ionize the target material and encourage it to settle on the substrate in the form of a thin film
-The energy level diagram for each layer, when CZTSe as a single layer HTL, the VoC (open circuit voltage) value was very low (as it can be seen on the tables), mainly due to VoC loss caused by its shallow valance band. Therefore, adding modified layer, it found that the added NiOx layer could make energy level more matched, thereby reducing VoC loss and increasing the ohmic contact to improve the device fill factors (FF)
-CZTSe combined with NiOx as a double layered HTL also improved the extraction and transfer process of the photo-induced carriers from pv layer. This is beneficial to reduce the recombination blocking probability of electrons and holes.
-On the XRD, peak 110 indicating the existence of Cu2S, 112 of CTZS, peak 213 and 204 of CTZSe.
-As-deposited CZTSe films have no diffraction peak phase can
be found and regarded as an amorphous structure.
-When the annealing temperature was 400 °C, no other peaks can be found, indicating that the film has (112) preferred orientation. As the annealing temp increase, the crystal planes of the kesterite-type CZTSe structure gradually appear.
-As the SEM image shows, at 400˚C, the films appears to be uniformly sized grains without aggregation (did not gather), as the temp increase, the film start to grow bigger, as the annealing temp affect the crystalline characteristic of the film
-All the CZTSe samples were found to be highly transparent with > 85% average transmittance in the wavelength region of 300–800 nm, when the NiOx layer was deposited on the surface of CZTSe annealed at different temperatures, its spectral distribution slightly decreases of 1–3% in the wavelength range of 300–800 nm.
-Therefore, depositing a NiOx layer on the CZTSe surface annealed at different temperature has little effect on optical transmittance.
As shown in Fig. 4(c), the absorption, on 600˚C annealed-CTZSe/NiOx double layer HTL absorbance more than 50% between 750-800nm, this significantly enhanced the light-harvesting and photo carrier transport of perovskite solar cells, which will contribute to improve the PCE (power conversion efficiency).
-PL spectral peak at about 768 nm was assigned to the luminescence emission from MAPbI3 perovskites. CZTSe-introduced HTL showed more effcient PL quenching obtained from the PL, especially in the case of 600 °C-annealed-CZTSe/NiOx double-layer HTL.
-The PL quenching was originated from the carrier extraction across the interface between MAPbI3 and double-layer HTL, which ascribes to the introduction of CZTSe/NiOx accelerates the charge extraction from perovskite layer and high mobility of CZTSe.
-This is in line with the theory, as the annealing temperature increased, a significant improvement od the performance PV was shown. This improvement could be due to the electrical and good optical transmittance properties of CZTSe, which is able to improve the charge extraction/transport process and avoid the incoming photon loss.
The perovskite solar cells with the different annealing temperatures of CZTSe of the CZTSe/NiOx double-layer HTL showed significantly improved photovoltaic performance.
-The devices with the 400 °C- and 500 °C-annealed CZTSe/NiOx double-layer HTLs, respectively, showed apparent drop in PCE mainly due to a significant fall in Jsc and relatively low FF. The fall performance were mainly attributed to a significant increase in the series resistance. While, the relatively low performance of the NiOx HTL based device was due to a significant reduction in FF.
-These results indicate that the CZTSe/NiOx double-layer HTL significantly affected the photovoltaic performance, and the improvement of device performance emanated from the charge extraction/transport process and the high hole mobility of CZTSe.
-The crystallinity of the pv film grown on the CZTSe/NiOx double layered HTL structure is better than that of PEDOT:PSS HTL, which displays the acidity and its hydrophylic, which is determinal for the cells stability. The improvement in stability might be explained by that the inserted sputterd-CZTSe act as an additional final blocking layer to protect cells from sour corrosion such as PEDOT:PSS, but also to weaken the penetration of moisture to a certain extent
-XRD analysis revealed that the crystallinity of the perovskite film grown on the CZTSe/NiOx double-layer HTL was better than that of PEDOT:PSS HTL.
