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Öğe Acetate-based ionic liquid engineering for efficient and stable CsPbI2Br perovskite solar cells with an unprecedented fill factor over 83%(Elsevier, 2024) Sadegh, Faranak; Ebic, Murat; Prochowicz, Daniel; Ans, Muhammad; Kruszynska, Joanna; Satapathi, Soumitra; Moghadam, MajidThe current investigation addresses the persistent challenge of poor ambient stability exhibited by inorganic lead halide perovskites, primarily stemming from intrinsic phase transitions and the presence of defect states. This area of research has been considerably unexplored thus far. On the other hand, the notable effects of ionic liquids (ILs) in improving both stability and efficiency of perovskite photovoltaics have been substantial. In line with these developments, this study endeavors to synergize these two critical domains by introducing an acetate (Ac)based IL into the inorganic perovskite precursor solution to tailor the crystal growth and charge carrier dynamics in CsPbI2Br films, resulting in prolonged stability and enhanced photovoltaic performance. The integration of 1-butyl-3-methylimidazolium acetate (BMIMAc) can indeed accelerate the crystallization of the inorganic perovskite film by interacting the Ac anion with uncoordinated Pb2+ cation in CsPbI2Br. This interaction prompts the formation of smaller grains, which in turn inhibits the creation of non-photoactive phases. Moreover, the presence of BMIMAc as a passivation agent introduces significant defect-healing capabilities, eliminated charge recombination, and increased hydrophobicity. This work endeavors to pave the way for high-efficiency, enduring, and more robust inorganic PSCs through the integration of innovative materials and advanced understanding of fundamental principles, resulting uniform and dense perovskite film. Accordingly, 1.1 mol% BMIMAc-passivated device enables an impressive efficiency of 15.6% with an unprecedented fill factor (FF) exceeding 83%. Remarkably, even after undergoing extended light-soaking for 600 h, the BMIMAc-passivated device retains approximately 85% of its initial efficiency.Öğe Eco-Friendly Boost for Perovskite Photovoltaics: Harnessing Cellulose-Modified SnO2 as a High-Performance Electron Transporting Material(Amer Chemical Soc, 2023) Ozkaya, Veysel; Sadegh, Faranak; Unal, Muhittin; Alkan, Bulent; Ebic, Murat; Ozturk, Teoman; Yilmaz, MucahitIn this study, a passivated tin oxide (SnO2) film is successfully obtained through the implementation of sodium carboxymethyl cellulose (Na-CMC) modifier agent and used as the electron transporting layer (ETL) within the assembly of perovskite solar cells (PSCs). The strategic incorporation of the Na-CMC modifier agent yields discernible enhancements in the optoelectronic properties of the ETL. Among the fabricated cells, the champion cell based on Na-CMC-complexed SnO2 ETL achieves a conversion efficiency of 22.2% with an open-circuit voltage (V-OC) of 1.12 V, short-circuit current density (J(SC)) of 24.57 mA/cm(2), and fill factor (FF) of 80.6%. On the other hand, these values are measured for the pristine SnO2 ETL-based control cell as V-OC = 1.11 V, J(SC) = 23.59 mA/cm(2), and FF = 76.7% with an efficiency of 20.1%. This improvement can be ascribed to the high charge extraction ability, higher optical transmittance, better conductivity, and decrease in the trap state density associated with the passivated ETL structure. In addition, the cells employing Na-CMC-complexed SnO2 ETL exhibit prolonged stability under ambient conditions during 2000 h. Based on the preliminary results, this study also presents a set of findings that could have substantial implications for the potential use of the Na-CMC molecule in both large-scale perovskite cells and perovskite/Si tandem configuration.Öğe Effect of 1,3-Disubstituted Urea Derivatives as Additives on the Efficiency and Stability of Perovskite Solar Cells(Amer Chemical Soc, 2022) Kruszynska, Joanna; Sadegh, Faranak; Patel, Manushi J.; Akman, Erdi; Yadav, Pankaj; Tavakoli, Mohammad Mahdi; Gupta, Sanjeev K.Additive engineering in perovskites precursor solution is one of the most effective methods to fabricate high-quality perovskite films. Finding proper additives for morphology improvement and passivation of the perovskite defects is critical to fabricate highly efficient and stable perovskite solar cells (PSCs). In this work, 1,3-disubstituted urea additives are employed to study the effect of different substituents at -NH moiety on the quality of the perovskite layer and device performance. By adding 1,3-diphenyl urea (Ph-urea) or 1,3-di(tert-butyl)urea (tBu-urea) into the precursors, the crystallization process leads to the formation of perovskite films with larger grains and lower defect densities as compared to the nonsubstituted urea additive. Using density functional theory (DFT) calculations and experimental spectro-scopic measurements, we found that the selected 1,3-disubstituted ureas are prone to form stronger coordination interaction with undercoordinated Pb2+ ions than the urea. Applying this additive engineering to the devices reduced the current density-voltage (J-V) hysteresis and improved the photovoltaic performance, resulting in maximum power conversion efficiencies of 21.7 and 21.2% for the Ph-urea and tBu-urea modified devices, respectively. In addition, the device with Ph-urea enhanced long-term stability, where it remains at 90% of its initial efficiency, while the device with tBu-urea degrades fast reaching 20% of its initial efficiency after aging for 90 days due to the high moisture permeability of tBu-urea.Öğe The effect of B-site doping in all-inorganic CsPbIxBr3-x absorbers on the performance and stability of perovskite photovoltaics(Royal Soc Chemistry, 2023) Akman, Erdi; Ozturk, Teoman; Xiang, Wanchun; Sadegh, Faranak; Prochowicz, Daniel; Tavakoli, Mohammad Mahdi; Yadav, PankajDespite the impressive efficiency of perovskite solar cells (PSCs), their operational stability is still hindered by the thermodynamic instability of the hybrid organic-inorganic absorber layer with ABX(3) structure (A: organic/inorganic cation, B: metal cation, X: halogen anion and mixtures thereof). Due to the hygroscopic and volatile nature of the organic cations, i.e., methylammonium (MA(+)), they show very poor stability not only against thermal stress but also moisture. Therefore, a photoactive material free from organic components could offer great opportunities to prolong the operational stability of devices. In this context, all inorganic CsPbIxBr3-x perovskites are meticulously developed in terms of their structural/thermal stability and have triggered increasing research interest due to great prospects in the commercialization of perovskite technology. However, besides relatively low performance, the poor phase stability of inorganic perovskites associated with lattice strain and vacancies still requires a thorough understanding and permanent solutions for tackling these problems. In this comprehensive review, the recently reported B-site doping strategy in inorganic CsPbIxBr3-x perovskite thin films, which has been elucidated to passivate the defects, tune the grain orientation, and enhance the lifetime of charge-carriers, is presented based on different B-site elements belonging to group IIIA, IVA and VA, alkaline-earth, transition, and lanthanide metals. Solutions for confronting these current problems are elaborated and an outlook on further strategies is given.Öğe Facile NaF Treatment Achieves 20% Efficient ETL-Free Perovskite Solar Cells(Amer Chemical Soc, 2022) Sadegh, Faranak; Akman, Erdi; Prochowicz, Daniel; Tavakoli, Mohammad Mahdi; Yadav, Pankaj; Akin, SeckinElectron transporting layer (ETL)-free perovskite solar cells (PSCs) exhibit promising progress in photovoltaic devices due to the elimination of the complex and energy-/timeconsuming preparation route of ETLs. However, the performance of ETL-free devices still lags behind conventional devices because of mismatched energy levels and undesired interfacial charge recombination. In this study, we introduce sodium fluoride (NaF) as an interface layer in ETL-free PSCs to align the energy level between the perovskite and the FTO electrode. KPFM measurements clearly show that the NaF layer covers the surface of rough underlying FTO very well. This interface modification reduces the work function of FTO by forming an interfacial dipole layer, leading to band bending at the FTO/perovskite interface, which facilitates an effective electron carrier collection. Besides, the part of Na+ ions is found to be able to migrate into the absorber layer, facilitating enlarged grains and spontaneous passivation of the perovskite layer. As a result, the efficiency of the NaF-treated cell reaches 20%, comparable to those of state-of-the-art ETL-based cells. Moreover, this strategy effectively enhances the operational stability of devices by preserving 94% of the initial efficiency after storage for 500 h under continuous light soaking at 55 degrees C. Overall, these improvements in photovoltaic properties are clear indicators of enhanced interface passivation by NaF-based interface engineering.