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Silane Capped ZnO Nanoparticles for Use as the Electron Transport Layer in Inverted Organic Solar Cells Junfeng Wei, Guoqi Ji, Chujun Zhang, Lingpeng Yan, Qun Luo, Cheng Wang, Qi Chen, Junliang Yang, Liwei Chen, and Chang-Qi Ma ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.8b01178 • Publication Date (Web): 08 Jun 2018 Downloaded from http://pubs.acs.org on June 8, 2018
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ACS Nano
Silane Capped ZnO Nanoparticles for Use as the Electron Transport Layer in Inverted Organic Solar Cells Junfeng Wei,
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Guoqi Ji, Chujun Zhang Lingpeng Yan Qun Luo, Cheng Wang, ξ Qi Chen, ξ ‡
Junliang Yang,* Liwei Chen, ξ Chang-Qi Ma
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Printable Electronics Research Center (SINANO), Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Collaborative Innovation Center of Suzhou Nano Science and Technology, Suzhou, 215123, P. R. China ‡
Hunan Key Laboratory for Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha 410083, Hunan, P. R. China §
ξ
University of Chinese, Academy of Sciences, Beijing, 100049, P. R. China
i-lab, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, 215123, P. R. China E-mail:
[email protected];
[email protected];
[email protected] ACS Paragon Plus Environment
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ABSTRACT:
Zinc oxide (ZnO) nanoparticles are widely used as the electron- transport layers (ETLs) materials in the organic solar cells, and are considered to be the candidate with the most potential for ETLs in roll-to-roll (R2R) printed photovoltaics. However, the tendency of the nanoparticles to aggregate reduces the stability of the metal oxides inks and creates many surface defects, which is a major barrier to its printing application. With the aim of improving the stability of metal oxide nanoparticles dispersions and suppressing the formation of surface defects, we prepared 3-aminopropyltrimethoxysilane (APTMS)-capped ZnO (ZnO@APTMS) nanoparticles through surface ligand exchange. The ZnO@APTMS nanoparticles exhibited excellent dispersibility in ethanol, an environmentally friendly solvent, and remained stable in air for at least one year without any aggregation. The capping of the ZnO nanoparticles with APTMS also reduced the number of surface adsorbed oxygen defects, improved the charge transfer efficiency, and suppressed the light-soaking effect. The thickness of the ZnO@APTMS ETL could reach 100 nm without an obvious decrease in the performance. Large-area APTMS-modified ZnO films were successfully fabricated through roll-to-roll micro-gravure printing and exhibited good performance in flexible organic solar cells. This work demonstrated the distinct advantages of this ZnO@APTMS ETL as a potential buffer layer for printed organic electronics.
Keywords: organic solar cells; ZnO nanoparticles; printable buffer layer; silane capping agent; long-term stability
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ACS Nano
Organic solar cells have attracted extensive attention in the field of renewable energy due to their advantages of low cost, light weight, flexibility, colorful, and roll-to-roll printing compatibility.1-3 Considerable efforts have been made to improve the power conversion efficiency by designing new donor and acceptor materials, controlling the phase separation morphology, optimizing the interface, etc. The highest performance achieved recently by ternary and tandem organic solar cells is over 14% for both,4,5 showing large potential of the organic solar cells for commercial and industrial application. Organic solar cells include the conventional and inverted structures, and among the two types, the inverted organic solar cells using an ITO electrode as the cathode and Ag or Al metal as the anode have been proven to be more stable than devices with the conventional structure.6 In the inverted organic solar cells, zinc oxide (ZnO) has been widely used as the electron transport layer (ETL) because it is cost effective, easily fabricated, and environmentally friendly. 7,8
Furthermore, the ZnO electron buffer layer has been proven to be the most promising ETL for
the roll-to-roll (R2R) printed photovoltaics to date.9 ZnO ETLs have been primarily prepared through a simple sol-gel method via spin-coating a ZnO sol precursor solution on a substrate, followed by annealing at approximately 200-350 oC for 30 min.10,11 The high-temperature annealing step of this process might be a big drawback in term of the fabrication of large area flexible photovoltaics due to the poor heat resistance of the typical plastic substrates. In comparison, the ZnO layer formed from ZnO nanoparticle formulations is a good choice as an ETL because of its low-temperature processability (
