期刊
NANO ENERGY
卷 51, 期 -, 页码 308-316出版社
ELSEVIER
DOI: 10.1016/j.nanoen.2018.06.058
关键词
All-oxide NWs; Core-shell NWs; Self-powered photodetectors; Fast photodetectors; ZnO-Cu2O heterojunction
类别
资金
- Knut & Alice Wallenberg Foundation [KAW 2016.0346]
- Swedish Foundations Consolidator Fellowship
- LTU Labfund program
- Kempe Foundation [JCK 1703]
- European Union's Horizon 2020 research and innovation programme [654002]
- European Commission
- VINNOVA through a VINNMER Marie Curie fellowship [2015-01513]
- University of Catania within the Piano della Ricerca di Ateneo
In this work, we present all-oxide p-n junction core-shell nanowires (NWs) as fast and stable self-powered photodetectors. Hydrothermally grown n-type ZnO NWs were conformal covered by different thicknesses (up to 420 nm) of p-type copper oxide layers through metalorganic chemical vapor deposition (MOCVD). The ZnO NWs exhibit a single crystalline Wurtzite structure, preferentially grown along the [002] direction, and energy gap E-g = 3.24 eV. Depending on the deposition temperature, the copper oxide shell exhibits either a crystalline cubic structure of pure Cu2O phase (MOCVD at 250 degrees C) or a cubic structure of Cu2O with the presence of CuO phase impurities (MOCVD at 300 degrees C), with energy gap of 2.48 eV. The electrical measurements indicate the formation of a p-n junction after the deposition of the copper oxide layer. The core-shell photodetectors present a photo-responsivity at 0 V bias voltage up to 7.7 mu A/W and time response <= 0.09 s, the fastest ever reported for oxide photodetectors in the visible range, and among the fastest including photodetectors with response limited to the UV region. The bare ZnO NWs have slow photoresponsivity, without recovery after the end of photo-stimulation. The fast time response for the core-shell structures is due to the presence of the p-n junctions, which enables fast exciton separation and charge extraction. Additionally, the suitable electronic structure of the ZnO-Cu2O heterojunction enables self-powering of the device at 0 V bias voltage. These results represent a significant advancement in the development of low-cost, high efficiency and self-powered photodetectors, highlighting the need of fine tuning the morphology, composition and electronic properties of p-n junctions to maximize device performances.
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