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Functional Inorganic Materials and Devices
Toward Highly Reproducible, Efficient and Stable Perovskite Solar Cells via Interface Engineering with CoO Nanoplates Yanfei Dou, Deng Wang, Guodong Li, Yinsheng Liao, Weihai Sun, Jihuai Wu, and Zhang Lan ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b11039 • Publication Date (Web): 12 Aug 2019 Downloaded from pubs.acs.org on August 12, 2019
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ACS Applied Materials & Interfaces
Toward Highly Reproducible, Efficient and Stable Perovskite Solar Cells via Interface Engineering with CoO Nanoplates Yanfei Dou, Deng Wang, Guodong Li, Yinsheng Liao, Weihai Sun, Jihuai Wu, Zhang Lan* Engineering Research Center of Environment-Friendly Functional Materials, Ministry of Education; Fujian Key Laboratory of Photoelectric Functional Materials; Institute of Materials Physical Chemistry, College of Materials Science & Engineering, Huaqiao University, Xiamen 361021, China KEYWORDS: Interface engineering; Planar perovskite solar cell; Reproducibility; Efficiency; Stability ABSTRACT: It is well known that the solution-processed polycrystalline perovskite films show a high density of parasitic traps and the defects mainly exist at grain boundaries and surfaces of polycrystal perovskite films, which would limit potential device performance by triggering the undesired recombination and impair device long-term stability by accelerating the degradation of perovskite films. In this regard, defect passivation is highly desirable for achieving efficient and stable perovskite solar cells (PSCs). Here, we report the fabrication of highly reproducible, efficient and stable PSCs via interface engineering with CoO nanoplates. By spin-coating
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suitable concentration of CoO nanoplates solution on the perovskite film a discontinuous CoO nanoplates modified layer is obtained, which is advantageous to achieving highly photovoltaic performance of the device because the uncovered perovskite crystalline grains can guarantee the unobstructed transport of holes from perovskite layers to hole transport layers. Furthermore, the hydrophobic oleylamine ligands capped CoO nanoplates are well filled in the boundaries of perovskite crystalline grains to effectively passivate the trap states, suppress dark recombination and enhance moisture-resistance. These benefits are propitious to achieving a 20.72% champion efficiency and a 20.20% steady-state efficiency of the devices with good reproducibility and stability. 1 INTRODUCTION Perovskite solar cells (PSCs) have become one of the most promising photovoltaic technologies because their power conversion efficiency (PCE) has sky-rocketed from 3.8% to 24.2% in about ten years and they can be fabricated with solution-processed methods.1-6 The charming natures of PSCs are mainly originated from the used organic-inorganc hybrid perovskite materials, which have splendid electronic and optical properties such as outstanding absorption coefficient, high charge carrier mobility, long carrier diffusion length and low excition binding energy.7-10 However, the solution-processed polycrystalline perovskite films show a high density of parasitic traps.11 It is reported that the trap density of polycrystalline perovskite films are much higher than those of single crystal ones (about 1015~1017 cm-3 versus 1010 cm-3).12-14 The defects mainly exist at grain boundaries and surfaces of polycrystal perovskite films, which would limit potential device performance by triggering the undesired recombination and impair device long-term stability by accelerating the degradation of
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ACS Applied Materials & Interfaces
perovskite films.15-17 In this regard, defect passivation is highly desirable for achieving efficient and stable PSCs. Interface engineering is considered as an effective way to minimize defects in polycrystal perovskite films or interfaces of the corresponding devices and simultaneously improve longterm stabiliy of the devices.18-25 Wang et al. did pioneer work in appling thin insulating polymer layers to form tunneling contacts at the cathode sides of inverted p-i-n planar PSCs, which effectively suppress the charge recombination at contacts and passivate the surface to increase device efficiency. Device with these insulating polymer layers achieved an enhanced PCE of 20.3% and dramatically increased water-resistance without futher encapsulation.26 S. H. TurrenCruz et al. prepared polymeric interlayers at both the electron and hole transporting interfaces to further enhance the efficiency and stability of formamidinium-based planar PSCs without Br and methylammonium (MA). The polymer-modified planar PSCs achieved a stabilized efficiency of 20.35% and exhibited obviously enhanced stability by aging at room temperature for 1000 hours of continuous maximum power point tracking in a nitrogen atmosphere compared with the unmodified ones.27 Apart from polymeric materials, some inorganic materials are also suitable for interface engineering.28-32 For instance, D. Koushik et al. deposited an ultra-thin Al2O3 layer on top of the perovskite absorber as a tunnel contact. The fabricated PSCs exhibited a stabilized PCE of 18%, a significant reduction in hysteresis loss, and enhanced long-term stability, superior to the unmodified ones.30 Nevertheless, effective interface engineering with these insulating materials requires fabrication of ultra-thin films (usually
