Unveiling the Role of the Metal Oxide/Sn Perovskite Interface Leading to Low Efficiency of Sn-Perovskite Solar Cells but Providing High Thermoelectric Properties (original) (raw)
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The Japan Society of Applied Physics, 2021
Tin halide perovskites (THPs) have appealing optoelectronic properties similar to lead halide perovskites (LHPs). However, THPs coated on metal oxide electrodes in normal-structure perovskite solar cells exhibit poor diode rectification, resulting in poor efficiency. This poor photoelectric performance in n−i−p-based THP solar cells is in contrast with LHP solar cells. We report that this deficient performance of THP solar cells is triggered by the defect states of the metal oxide layer. The defect states of the metal oxide can trap the electrons from the THP, leading to the prompt formation of Sn(IV), which will increase the carrier density and lead to poor photoelectric performance. This observation was supported by the ultraviolet-photoelectron spectroscopic measurements of inorganic thin films Al 2 O 3 , SnO 2 , TiO 2 , ZnO, and ZrO 2. However, this self-doping phenomenon resulting in the increase in carrier density can be applied to thermoelectric studies. Using CsSnI 3 /ZrO 2 nanocomposites as thermoelectric active layers, we report a power factor of 186.58 μW/mK 2 measured at room temperature, which is better than the 148.61 μW/mK 2 of the original CsSnI 3 thin film.
Recent Advancements in Tin Halide Perovskite-Based Solar Cells and Thermoelectric Devices
Nanomaterials
The excellent optoelectronic properties of tin halide perovskites (Sn-PVKs) have made them a promising candidate for replacing toxic Pb counterparts. Concurrently, their enormous potential in photon harvesting and thermoelectricity applications has attracted increasing attention. The optoelectronic properties of Sn-PVKs are governed by the flexible nature of SnI6 octahedra, and they exhibit extremely low thermal conductivity. Due to these diverse applications, this review first analyzes the structural properties, optoelectronic properties, defect physics, and thermoelectric properties of Sn-PVKs. Then, recent techniques developed to solve limitations with Sn-PVK-based devices to improve their photoelectric and thermoelectric performance are discussed in detail. Finally, the challenges and prospects for further development of Sn-PVK-based devices are discussed.
Crystals
Perovskite solar cells were fabricated with SnO2 thin films as a window layer and electron transport layer by thermal evaporation. Fundamental characteristics of SnO2 thin films to determine the performance of solar cells were investigated in an optical and electrical manner, varying annealing temperatures. It is found the crystallinity and the presence of localized energy states play a key factor to control the properties of SnO2. In addition, XPS was used to confirm the stoichiometry of the SnO2 thin films, indicating a better charge collection on the annealed SnO2 samples. The SnO2 thin films annealed at 300 °C exhibited desirable optical and electrical properties for the enhanced performance of solar cells. The results show that thermally evaporated SnO2 thin films can be precisely engineered and controlled for mass production and more practical industrialization of perovskite solar cells.
Small, 2019
Nanostructured tin (IV) oxide (SnO2) is emerging as an ideal inorganic electron transport layer in n–i–p perovskite devices, due to superior electronic and low‐temperature processing properties. However, significant differences in current–voltage performance and hysteresis phenomena arise as a result of the chosen fabrication technique. This indicates enormous scope to optimize the electron transport layer (ETL), however, to date the understanding of the origin of these phenomena is lacking. Reported here is a first comparison of two common SnO2 ETLs with contrasting performance and hysteresis phenomena, with an experimental strategy to combine the beneficial properties in a bilayer ETL architecture. In doing so, this is demonstrated to eliminate room‐temperature hysteresis while simultaneously attaining impressive power conversion efficiency (PCE) greater than 20%. This approach highlights a new way to design custom ETLs using functional thin‐film coatings of nanomaterials with opt...
Review on Recent Progress of All‐Inorganic Metal Halide Perovskites and Solar Cells
Advanced Materials, 2019
perovskite-based solar cells (PSCs) have reached a certified power conversion efficiency (PCE) of 24.2% in 2019, [19] which is comparable with that of copper indiumgallium diselenide (CIGS) [20] and siliconbased solar cells. The general chemical formula of a perovskite compound can be described as ABX 3 , where A is a monovalent cation (methylammonium (CH 3 NH 3 + (MA +)), formamidinium (CH(NH 2) 2 + (FA +)), cesium, etc.), B is a divalent metal cation (Pb 2+ , Sn 2+ , etc.), and X is occupied by a halide counterion (Cl − , Br − , and I −). It is possible to form mixed compounds with respect to each site. The commercialization of hybrid perovskites requires materials that are thermodynamically stable and can withstand various thermal stressing tests, including natural daynight cycling and exposure to full sunlight. The organic parts in perovskites (such as MA + or FA +) cannot endure high temperature and thus presents a longterm stability issue for devices under operation. Among the various degradation and decomposition pathways of hybrid perovskite, which depend on environmental factors such as humidity and illumination, a common theme is the low thermal stability of these perovskites, even in inert atmosphere. [21-23] For example, release of CH 3 NH 2 has been reported in MA-based perovskite films at temperatures of 80 °C, indicating decomposition of MA. [24] However, standard operational conditions for photovoltaics require materials and devices to be stable at this temperature. Therefore, the replacement of the organic parts by inorganic components (Cs +) is expected to dramatically increase the long-term stability. [23,25,26] It has been widely reported that even a small amount of cesium can greatly enhance the thermal stability of organic-inorganic hybrid perovskites. [27,28] For example, FA 0.83 Cs 0.17 Pb(I 0.6 Br 0.4) 3 demonstrates both thermal and moisture stability, and stability to operation in the presence of oxygen. [29] An early report by Hodes [30] shows that thin films of the inorganic perovskite CsPbBr 3 can be prepared with a two-step method. The solar cells employing these layers yield an impressive high open circuit voltage (V oc) of 1.32 V. These results, as the authors emphasize, indicate that the organic moiety is not an essential component in constructing high-performance perovskite materials and devices. Since then, with numerous publications each year, the inorganic PSCs research community is keeping highly active, including novel deposition methods All-inorganic perovskites are considered to be one of the most appealing research hotspots in the field of perovskite photovoltaics in the past 3 years due to their superior thermal stability compared to their organic-inorganic hybrid counterparts. The power-conversion efficiency has reached 17.06% and the number of important publications is ever increasing. Here, the progress of inorganic perovskites is systematically highlighted, covering materials design, preparation of high-quality perovskite films, and avoidance of phase instabilities. Inorganic perovskites, nanocrystals, quantum dots, and lead-free compounds are discussed and the corresponding device performances are reviewed, which have been realized on both rigid and flexible substrates. Methods for stabilization of the cubic phase of low-bandgap inorganic perovskites are emphasized, which is a prerequisite for highly efficient and stable solar cells. In addition, energy loss mechanisms both in the bulk of the perovskite and at the interfaces of perovskite and charge selective layers are unraveled. Reported approaches to reduce these charge-carrier recombination losses are summarized and complemented by methods proposed from our side. Finally, the potential of inorganic perovskites as stable absorbers is assessed, which opens up new perspectives toward the commercialization of inorganic perovskite solar cells.
Challenges and Potential of Perovskite Solar Cells
Journal of Ravishankar University (Part-B: Science), 2023
A solar cell is a device that converts sunlight into electricity. There are different types of solar cells but in this literature mainly focuses on a type of new dominant solar cell material that has the name organo-metal halide perovskite, namely known as perovskite solar cells, in shortly PSCs. In this respect, the efficiency of power conversion is taken into account to replace the dominancy of traditional and second generation solar cell fields by perovskite solar cells. Perovskite solar cell is a type of solar cell including a perovskite structure, usually a hybrid organic-inorganic lead or tin halide-based material. In this review, a comprehensive study of the perspective challenges and their potential has been highlighted for their future application. There are rigorous research efforts in aspects of device engineering, including physical and chemical passivation, and the use of a wide variety of organic and inorganic additives to develop the advanced PSCs.
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.