Fast Crystallization and improved Stability of Perovskite Solar Cells with Zn2SnO4 Electron Transporting Layer: Interface Matters (original) (raw)
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Journal of Power Sources, 2019
In planar perovskite solar cells, the electron transport layer (ETL) plays a vital role in effective extraction and transportation of photogenerated electrons from the perovskite layer to the cathode. Ternary metal oxides exhibit excellent potentials as ETLs since their electrical and optical properties are attunable through simple compositional adjustments. In this paper, we demonstrate the use of solution-processed zinc oxide (ZnO) and zinc tin oxide (ZTO) films as highly efficient ETLs for perovskite solar cells. We observe poor compatibility between ZnO and perovskite which impedes device reproducibility, stability, and performance unlike ZTO ETL devices. Furthermore, we modify the ZTO/perovskite interface by introducing a thin passivating SnO 2 interlayer. The Zn 1 Sn 1 O x /SnO 2 ETL device demonstrates paramount power conversion efficiency (PCE) of 19.01% with corresponding short circuit current density (J sc), open circuit voltage (V oc), and fill factor (FF) values of 21.93 mA cm À 2 , 1.10 V, and 78.82%. Moreover, the Zn 1 Sn 1 O x /SnO 2 ETL device displays superior stability, maintaining 90% of its initial PCE after 90 days in the absence of encapsulation at relative humidity of 30-40%. Enhancement in charge extraction, favourable energy alignment, and reduction in recombination sites greatly contribute to the optimal performance, stability, and reproducibility of the Zn 1 Sn 1 O x /SnO 2 ETL device.
Bilayer SnO2 as Electron Transport Layer for Highly Efficient Perovskite Solar Cells
ACS Applied Energy Materials, 2018
Tin Oxide (SnOR 2 R) has been reported as a promising electron transport layer (ETL) for planar heterojunction perovskite solar cells (PSCs). This work reports a low temperature solutionprocessed bilayer SnOR 2 R as an efficient ETL in gas-quenched planar-heterojunction methylammonium lead iodide (MAPbIR 3 R) perovskite solar cells. SnOR 2 R nanoparticles were employed to fill the pin-holes of sol-gel SnOR 2 R layer and form a smooth and compact bilayer structure. The PCE of bilayer devices has increased by 30% compared with sol-gel reference device and the JR sc R, VR oc R and FF has been improved simultaneously. The superior performance of bilayer SnOR 2 R is attributed to the reduced current leakage, enhanced electron extraction characteristics, and mitigated the trap-assisted interfacial recombination, via X-Ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and space-charge limited current-voltage (SCLC) analysis.
Hybrid Mesoporous TiO2/ZnO Electron Transport Layer for Efficient Perovskite Solar Cell
Molecules
In recent years, perovskite solar cells (PSCs) have gained major attention as potentially useful photovoltaic technology due to their ever-increasing power-conversion efficiency (PCE). The efficiency of PSCs depends strongly on the type of materials selected as the electron transport layer (ETL). TiO2 is the most widely used electron transport material for the n-i-p structure of PSCs. Nevertheless, ZnO is a promising candidate owing to its high transparency, suitable energy band structure, and high electron mobility. In this investigation, hybrid mesoporous TiO2/ZnO ETL was fabricated for a perovskite solar cell composed of FTO-coated glass/compact TiO2/mesoporous ETL/FAPbI3/2D perovskite/Spiro-OMeTAD/Au. The influence of ZnO nanostructures with different percentage weight contents on the photovoltaic performance was investigated. It was found that the addition of ZnO had no significant effect on the surface topography, structure, and optical properties of the hybrid mesoporous elec...
Double-layered ZnO nanostructures for efficient perovskite solar cells
Nanoscale, 2014
To date, a single layer of TiO 2 or ZnO has been the most successful implementations of any electron transport layer (ETL) in solutionprocessed perovskite solar cells. In a quest to improve the ETL, we explore a new nanostructured double-layer ZnO film for mesoscopic perovskite-based thin film photovoltaics. This approach yields a maximum power conversion efficiency of 10.35%, which we attribute to the morphology of oxide layer and to faster electron transport. The successful implementation of the low-temperature hydrothermally processed double-layer ZnO film as ETL in perovskite solar cells highlights the opportunities to further improve the efficiencies by focusing on the ETL in this rapidly developing field.
ACS Applied Energy Materials
Solution processed metal halide perovskite materials have revealed outstanding optoelectronic features that make them uniquely suited for photovoltaic applications. Although a rapid progress has led to performances similar to inorganic thin film technologies, the fabrication method of some of the most widely used electron selective layers, based on either mesoporous architectures or high annealing temperatures, may limit yet a future large scale production. In that regard, planar perovskite solar cell configurations that can be processed at low temperatures are more desirable. Herein, we demonstrate that a few tens of nanometers thick bilayer, made of two types of inorganic oxide nanoparticles, can perform as a robust and low temperature processed electron selective contact for planar perovskite solar cells. Aside from boosting the average efficiency of planar opaque devices, the proposed method allowed us to preserve the main photovoltaic characteristics when thinner active layers, usually exhibiting a non-continuous morphology, were integrated for semi-transparent cells. By providing excellent electronic and coverage features against the bottom electrode, this novel configuration may hence offer an alternative route to approach future inexpensive printable methodologies for the fabrication of efficient low temperature perovskite solar cells.
Fast and low temperature growth of electron transport layers for efficient perovskite solar cells
Journal of materials chemistry. A, Materials for energy and sustainability, 2015
We describe a fast, simple and low temperature electrochemical technique for the preparation of zinc oxide layers on rigid and flexible substrates. The layers, prepared from a zinc nitrate precursor, are of high structural and optical quality. They have been optimized to be applied as efficient electron transport layers in CH 3 NH 3 PbI 3-sensitized perovskite solar cells (PSCs). We show that an electrodeposition time of only two minutes and a low processing temperature are sufficient to fabricate solar cells with a power conversion efficiency close to 11%, with a high short circuit current and a small J-V curve hysteresis. The key parameters of the cell functioning have been analyzed over a large applied voltage range by the impedance spectroscopy technique. The solar cell characteristic changes with the ZnO layer deposition time are explained by the variation of the recombination and charge transfer resistances.
Inorganic Electron Transport Materials in Perovskite Solar Cells
Advanced Functional Materials, 2020
In the past decade, the perovskite solar cell (PSC) has attracted tremendous attention thanks to the substantial efforts in improving the power conversion efficiency from 3.8% to 25.5% for single-junction devices and even perovskite-silicon tandems have reached 29.15%. This is a result of improvement in composition, solvent, interface, and dimensionality engineering. Furthermore, the long-term stability of PSCs has also been significantly improved. Such rapid developments have made PSCs a competitive candidate for next-generation photovoltaics. The electron transport layer (ETL) is one of the most important functional layers in PSCs, due to its crucial role in contributing to the overall performance of devices. This review provides an up-to-date summary of the developments in inorganic electron transport materials (ETMs) for PSCs. The three most prevalent inorganic ETMs (TiO2, SnO2, and ZnO) are examined with a focus on the effects of synthesis and preparation methods, as well as an introduction to their application in tandem devices. The emerging trends in inorganic ETMs used for PSC research are also reviewed. Finally, strategies to optimize the performance of ETL in PSCs, effects the ETL has on J–V hysteresis phenomenon and longterm stability with an outlook on current challenges and further development are discussed.
Advanced Energy Materials, 2015
In recent years, a major breakthrough in performance enhancement has been achieved using lead organo halide perovskite light absorbers which has taken the spotlight in the broad area of emerging thin fi lm photovoltaics. [ 6-16 ] Perovskite materials promise to yield inexpensive solar cells owing to the earthabundance and low cost of the primary materials and to the opportunity to solution-manufacture large area panels via continuous and high throughput roll-toroll methods. [ 17 ] To achieve highly effi cient and low cost perovskite cells, efforts have been made mainly in two distinct directions; to modify either electron-injecting nanostructured oxide layers or to develop the nonelectron-injecting-type layers. In the case of electron injecting oxide systems mesoscopic TiO 2 is still one of the most widely employed electron transporting materials (ETMs) in mesoscopic devices. [ 18,19 ] It would be of great interest if all the layers used to fabricate the perovskite devices could be solution-processed at low temperature, thus opening up the routes for high throughput and continuous manufacturing on glass and on plastic substrates at a very low cost. [ 20 ] In this regard, ZnO-based nanostructures have attracted great attention in the dye-sensitized solar cell (DSSC) area as an alternative ETM to the conventional TiO 2 , because of their excellent electrical/optical characteristics that can be tuned easily by manipulating the morphology, doping, and composition. [ 21-23 ] Moreover, ZnO has several orders of magnitude higher conductivity than TiO 2 which can promote faster electron transport and can be easily solution-processed at low temperature with high structural quality and in a wide range of microstructures using different techniques. [ 24-27 ] Kelly and co-workers [ 28 ] have obtained remarkably effi cient (15.4%, in the reverse direction) perovskite devices based on planar spin-coated ZnO electron transporting layers (ETLs) approaching the performance (19.3%, in the reverse direction) of TiO 2-based ETL. [ 29 ] However, recent progress in the development of effi cient perovskite solar cells based on ZnO as a mesostructured ETM (e.g., nanoparticulate fi lm or nanorod (NR) array) has pushed the power conversion effi ciency (PCE) to 12% (in reverse direction), [ 30-34 ] which is still inferior to comparable mesostructured TiO 2 ETMs (with Signifi cant effi ciency improvements are reported in mesoscopic perovskite solar cells based on the development of a low-temperature solution-processed ZnO nanorod (NR) array exhibiting higher NR aspect ratio, enhanced electron density, and substantially reduced work function than conventional ZnO NRs. These features synergistically result in hysteresis-free, scan-independent, and stabilized devices with an effi ciency of 16.1%. Electron-rich, nitrogendoped ZnO (N:ZnO) NR-based electron transporting materials (ETMs) with enhanced electron mobility produced using ammonium acetate show consistently higher effi ciencies by one to three power points than undoped ZnO NRs. Additionally, the preferential electrostatic interaction between the nonpolar facets of N:ZnO and the conjugated polyelectrolyte polyethylenimine (PEI) has been relied on to promote the hydrothermal growth of high aspect ratio NR arrays and substantially improve the infi ltration of the perovskite light absorber into the ETM. Using the same interactions, a conformal PEI coating on the electron-rich high aspect ratio N:ZnO NR arrays is successfully applied, resulting in a favorable work function shift and altogether leading to the signifi cant boost in effi ciency from <10% up to >16%. These results largely surpass the state-of-the-art PCE of ZnO-based perovskite solar cells and highlight the benefi ts of synergistically combining mesoscale control with doping and surface modifi cation.