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Al2O3 Underlayer Prepared by Atomic Layer Deposition for Efficient Perovskite Solar Cells
| Content Provider | Semantic Scholar |
|---|---|
| Author | Zhang, Jinbao Hultqvist, Adam Zhang, Tian Jiang, Liangcong Ruan, Changqing Yang, Li Cheng, Yi-Bing Edoff, Marika Johansson, Erik M. J. |
| Copyright Year | 2017 |
| Abstract | Organic–inorganic hybrid perovskite solar cells (PSCs) have in the past few years attracted intense attention in the solar cell community due to the demonstrated high power conversion efficiency (PCE) of above 20 %. 2] The high performance of PSCs can mainly be attributed to the excellent properties of the perovskite, such as strong and broad light absorption, long charge-carrier diffusion length, and high ambipolar conductivity. Besides these good material properties, careful perovskite compositional engineering, interfacial materials development, and device configuration optimization are required to create great PSCs. In the standard n-i-p type of PSC configuration (Figure 1 a), after the light excitation in the perovskite, the charge separation is driven by the interfacial energy barriers and therefore mainly occurs at the interfaces between the perovskite and the electron transport material (ETM) on one side and between the perovskite and the hole transport material (HTM) on the other. After electron conduction through the ETM and hole conduction through the HTM in the opposite direction, the charges are finally collected at the two conductive contacts, for example, fluorine-doped tin oxide (FTO) at the ETM side and metallic gold at the HTM side. Based on reported energy levels for different components, a diagram representing the charge transfer and transport processes in PSCs is shown in Figure 1 b. 18] However, there are also some unfavorable charge recombination processes that occur simultaneously; for example, electrons located in mesoTiO2 and FTO can recombine with holes in the perovskite at the interface. These charge recombination processes could significantly influence the open-circuit voltage (Voc) and shortcircuit current (Jsc) and thus the PCE. To avoid the aforementioned recombination processes, an underlayer, also called a compact layer, is a vital component between the current collector FTO and the perovskite layer in obtaining high photon conversion efficiency. However, to date only a few reports have concerned the development of new underlayers for PSCs other than the conventional TiO2 prepared by spray pyrolysis. Perovskite solar cells, as an emergent technology for solar energy conversion, have attracted much attention in the solar cell community by demonstrating impressive enhancement in power conversion efficiencies. However, the high temperature and manually processed TiO2 underlayer prepared by spray pyrolysis significantly limit the large-scale application and device reproducibility of perovskite solar cells. In this study, lowtemperature atomic layer deposition (ALD) is used to prepare a compact Al2O3 underlayer for perovskite solar cells. The thickness of the Al2O3 layer can be controlled well by adjusting the deposition cycles during the ALD process. An optimal Al2O3 layer effectively blocks electron recombination at the perovskite/fluorine-doped tin oxide interface and sufficiently transports electrons through tunneling. Perovskite solar cells fabricated with an Al2O3 layer demonstrated a highest efficiency of 16.2 % for the sample with 50 ALD cycles (ca. 5 nm), which is a significant improvement over underlayer-free PSCs, which have a maximum efficiency of 11.0 %. Detailed characterization confirms that the thickness of the Al2O3 underlayer significantly influences the charge transfer resistance and electron recombination processes in the devices. Furthermore, this work shows the feasibility of using a high band-gap semiconductor such as Al2O3 as the underlayer in perovskite solar cells and opens up pathways to use ALD Al2O3 underlayers for flexible solar cells. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://researchmgt.monash.edu/ws/portalfiles/portal/300103597/300103451_oa.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
