Perovskite solar cells (PSCs) have gained significant attention as a promising photovoltaic technology due to their excellent power conversion efficiency (PCE) and cost-effective fabrication methods. However, ensuring long-term stability and addressing environmental concerns are vital challenges for successful commercialization. In this study, we explore metal oxide-based thin film encapsulation methods to enhance the performance and durability of PSCs. We considered back surface modification for flexible PSCs, as well as top surface encapsulation applicable to both rigid and flexible devices. Our results reveal increased operational stability and device performance, effectively addressing critical challenges in PSC commercialization.
KEYWORDS: Nanoparticles, Perovskite, Atomic layer deposition, Solar cells, Thin films, Tin, Thin film solar cells, Thin film deposition, Oxides, Interfaces
Tin oxide thin is a promising electron transport layer (ETL) for perovskite solar cells due to its excellent electronic properties and high thermal stability of SnO2. In addition, unlike TiO2 and ZnO, SnO2 does not have high photocatalytic activity and therefore would improve device stability under illumination compared to devices with titania or ZnO ETLs, and it can be deposited at low temperatures which makes it compatible with flexible devices. However, surface roughness, conformal coating, surface defects of SnO2, as well as its energy level alignment with the perovskite layer, affect the performance and stability of perovskite solar cells. In this study, we utilized ALD, sol-gel deposition and nanoparticle spin coating method to prepare SnO2 thin films and apply them as ETLs for planar perovskite solar cells. The obtained results indicate that the method of preparation of SnO2 significantly affects the solar cell performance. To improve the device performance, we investigated SnO2 bilayers to attempt to combine advantages of individual coating approaches. For an optimized order of layers to achieve efficient charge extraction across the interface, improved performance can be obtained compared to single layer SnO2 electron transport layers. Reasons for the performance improvement are discussed.
Metal oxide materials for solid state gas sensors has attracted lots of attention in the past few decades due to its low fabrication cost, small device size and potential application in toxic gases detection. SnO2 is one of the favorable materials since it has outstanding performance towards the detection of various gases. Its sensing mechanism in brief was based on the change in charge carrier density of the materials due to the presence of gas molecules and the change was determined by measuring the resistance or capacitance. Despite of its great success, researches has continue to further optimize the selectivity, sensitivity, response time and more importantly lowering the working temperature of the material. In this work, SnO2 nanostructures with metal nanoclusters on the surface was prepared. The incorporation of different metal nanoclusters would offer feasibility on the selection of gas detection. The energy level alignment and the Schottky barriers at the metal-metal oxide interface would further improve the sensitivity and response time of the materials. The surface plasmon generated by the metal nanoclusters utilizing visible light could lower the operation temperature and enhance sensitivity by offering more charge carriers. The SnO2 nanofiber in this work was prepared by a scalable electrospinning method and the Ag and Au nanoclusters were prepared by sputtering or thermal evaporation. Effect of the SnO2 morphology, size and distribution of the metal nanoclusters and the illumination on the device performance will be investigated and the detail working mechanism will be discussed.
TiO2 thin film photocatalysis has suffered from poor photocatalytic efficiency due to its low surface area-to-volume ratio. The efficiency can be enhanced by narrowing the bandgap, defect engineering or introducing surface plasmonic effect. However, the fabrication process is normally complicated and time consuming. This work offers a simple method to fabricate disordered defect-rich black TiO2 ultrathin film by atomic layer deposition (ALD). Surface defects of TiO2 have been suggested to play a significant role in the process of photocatalysis. With ALD, the bandgap and surface defects of the material can be controlled effectively through the deposition parameters. Surface plasmonic effects could also be introduced by the deposition of Ag nanoclusters via simple thermal evaporation. Absorption at ~450 nm was significantly enhanced. The overall photocatalytic behavior of composite material is greatly boosted and we observed an excellent efficiency towards the degradation of organic pollutants such as bisphenol A. The mechanism of surface plasmonic enhanced black TiO2 photocatalysis was studied by in-situ infrared atomic force microscope (IR-AFM) under the illumination of different wavelength. The reaction sites of the composite materials were determined accurately and the working mechanism was discussed.
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