Thermal EvaporationOxidation Deposited Aluminum Oxide as an Interfacial Modifier to Improve the Performance and Stability of Zinc Oxide-Based Planar Perovskite Solar Cells (original) (raw)
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ACS Energy Letters, 2018
Herein, we achieved, air-stable low-temperature processed PSC (L-PSC) using alkalimetal modified ZnO ETLs. Using a simple chemical alkali-metal modification method, the surface defects of the ZnO were effectively passivated. As a result, the interfacial decomposition reactions were suppressed, while raising the Fermi energy level and enhancing electron mobility. The improved interfacial charge transfer and internal electric field in the developed L-PSC using K modified ZnO (ZnO-K) exhibited an improved power conversion efficiency (PCE) of 19.91% with negligible hysteresis, while a pristine ZnO based L-PSC exhibited a PCE of 16.12% with significant hysteresis. The ZnO-K based L-PSC also exhibited remarkably higher long-term airstorage stability (91% retention after 800 h) than pristine ZnO based L-PSCs (36% retention after 800 h) due to the suppressed decomposition reactions. The PCE and air-stability of our L-PSC with the modified ZnO are among the highest reported for PSCs processed ≤ 150 °C .
Journal of Materials Science: Materials in Electronics, 2020
ZnO is a promising electron transport material with high electron mobility compared to TiO 2 and SnO 2. However, its high basicity and the presence of hydroxyl groups at the ZnO surface induces thermochemical decomposition of hybrid perovskites though proton transfer reactions. In perovskite solar cells (PSCs), these deprotonation reactions produce chemical products at the interface between ZnO and perovskite, which obstacle charge carrier extraction process and lead to low efficiency of the solar cells. In this work, PC 71 BM thin films of three different thickness, 19, 11 and 6 nm, were deposited on top of ZnO layers, prepared by sol-gel spin coating and annealed at 150°C. It is found that low temperature prepared ZnO films contain deep trap states, and the effective optical band gap of ZnO/PC 71 BM double layers is slightly reduced with the thickness of the fullerene derivative. The presence of an interfacial PC 71 BM layer on top of ZnO enhances the stability of the upcoming perovskite coatings and promotes the passivation of trap states at the ZnO surface. Interestingly, the best PC 71 BM-passivated PSC, fabricated under relative humidity (RH) of 60-65%, achieves a maximum power conversion efficiency (PCE) of 13.3%, whereas those PSCs with only ZnO as the electron transport layer show an average PCE of 5.5%. However, the stability under continuous illumination of PC 71 BM based PSCs is significantly lower than expected, probably due to the PC 71 BM degradation under high RH conditions.
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.
SnO2/ZnO Heterostructure as an Electron Transport Layer for Perovskite Solar Cells
Materials Research, 2021
This work reports a study of the room-temperature synthesis of a SnO 2 /ZnO bilayer by magnetron sputtering. Morphological, optical, and electrical properties of the bilayer were investigated for different thicknesses of SnO 2. Morphology was studied using profilometry and field emission scanning electron microscopy. The optical transmittances of the ZnO films and of the SnO 2 /ZnO combination were high (about 80%) in the visible, and the SnO 2 film did not alter the optical properties of the ZnO, which would act as a transparent contact electrode in a perovskite solar cell.
2019
In this work, for the first time, we intentionally deposit an ultrathin layer of excess methyl ammonium iodide (MAI) on top of a methyl ammonium lead iodide (MAPI) perovskite film. Using photoelectron spectroscopy, we investigate the role of excess MAI at the interface between perovskite and spiro-MeOTAD hole transport layer in standard structure perovskite solar cells (PSCs). We found that interfacial, favorable, energy-level tuning of the MAPI film can be achieved by controlling the amount of excess MAI on top of the MAPI film. Our XPS results reveal that MAI dissociates at low thicknesses (< 16 nm) when deposited on MAPbI 3. It is not the MAI layer, but the dissociated species that leads to the interfacial energy-level tuning. Optimized interface energetics were verified by solar cell device testing, leading to both an increase of 19% in average steady state power conversion efficiency (PCE) and significantly improved reproducibility, which is represented by a much lower PCE standard deviation (from 15 ± 2% and 17.2 ± 0.4%).
Fabrication parameters of low-temperature ZnO-based hole-transport-free perovskite solar cells
Perovskite solar cells (PSCs) are a new generation solar cells. Low-Temperature techniques are used for fabrication PSCs on a flexible substrate that has a low thermal tolerance. In this paper, low-temperature PSCs with ZnO nanoparticles were prepared as electron transport material (ETM) without hole transport material (HTM). Effects of some of the fabrication parameters of low-temperature ZnO based PSCs without HTM, on their principal characteristics and performance, were investigated. Parameters such as the concentration of ZnO nanoparticles (NPs) dispersion, spin coating speed of ZnO NPs, and concentration of CH 3 NH 3 I on characteristics and performance of fabricated low-temperature PSCs were studied. The study shows that by changing these parameters, the performance of the fabricated PSCs changes considerably.
Frontiers in Chemistry, 2022
Rapid improvement in efficiency and stabilities of perovskite solar cells (PSCs) is an indication of its prime role for future energy demands. Various research has been carried out to improve efficiency including reducing the exciton recombination and enhancement of electron mobilities within cells by using electron transport material (ETM). In the present research, electrical, optical, and depletion width reduction properties of low temperature processed ZnO electron transport layer-based perovskite solar cells are studied. The ZnO thin films vary with the concentration of Al doping, and improvement of optical transmission percentage up to 80% for doped samples is confirmed by optical analysis. Reduction in electrical resistance for 1% Al concentration and maximum conductivity 11,697.41 (1/Ω-cm) among the prepared samples and carrier concentration 1.06×1022 cm−3 were corroborated by Hall effect measurements. Systematic impedance spectroscopy of perovskite devices with synthesized E...
Advanced Energy Materials, 2018
layers and charge selecting buffer layers (i.e., electron-transporting layer (ETL) and hole-transporting layer (HTL)) are the key elements that determine the performance of PSCs. [5,8-12] The current state-of-the-art performance of PSCs is attained using high-temperature (≈500 °C)-sintered mesoporous TiO 2 as ETL, and spiro-OMeTAD as HTL. [1,2,13,14] In this type of PSC, the TiO 2 ETL is the process temperature determining material, while the perovskite active layers and HTLs can be prepared at relatively lower temperature (<150 °C). [2,4,5,10,15] To realize the PSC fabrication at lower temperature using various substrates, such as flexible plastics, [1,15,16] much effort has been made to develop high-performance low-temperature-processable ETLs for PSCs. [4,17-21] ZnO is a promising ETL candidate for PSCs because of easy solution processability, good optoelectronic properties, and appropriate work function. [18,19,22-30] Solution-processed ZnO has been successfully employed as ETL for other thin film solar cells such as organic photovoltaic devices and colloidal quantum dot solar cells. [23,26,29-33] Although there are some