Research Article Cite This: ACS Appl. Mater. Interfaces 2019, 11, 24459−24467
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High-Performance Flexible Ultraviolet Photodetectors Based on AZO/ZnO/PVK/PEDOT:PSS Heterostructures Integrated on Human Hair Xinglai Zhang,† Jing Li,† Wenjin Yang,† Bing Leng,‡ Pingjuan Niu,*,§ Xin Jiang,† and Baodan Liu*,†,∥
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Shenyang National Laboratory for Materials Science (SYNL), Institute of Metal Research (IMR), Chinese Academy of Sciences (CAS), No. 72 Wenhua Road, Shenyang 110016, China ‡ Department of Plastic Surgery, The First Affiliated Hospital of China Medical University, No. 155 North Nanjing Street, Shenyang 110001, China § School of Electrical Engineering and Automation, Tianjin Polytechnic University, No. 399 Binshuixi Road, Tianjin 300387, China ∥ State Key Laboratory of Optoelectronic Materials and Technologies and School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, P. R. China S Supporting Information *
ABSTRACT: Flexible optoelectronics is an emerging research field that has attracted a great deal of interest in recent years due to the special functions and potential applications of these devices in flexible image sensors, optical computing, energy conversion devices, the Internet of Things, and other technologies. Here, we examine the high-performance ultraviolet (UV) photodetectors using AZO/ZnO nanorods/PVK/PEDOT:PSS heterostructures integrated on human hair. Due to the precise interfacial energy-level alignment among all layers and superior mechanical characteristics of human hair, the as-obtained photodetector shows a fast response time, high photoresponsivity, and excellent flexibility. According to integrate 7 heterostructures as 7 display pixels, the flexible UV-image sensor has superior device performance and outstanding flexibility and can produce vivid and accurate images of Arabic numerals from 0 to 9. Different combinations of the two heterostructures can also be used to achieve flexible photon-triggered logic functions, including AND, OR, and NAND gates. Our findings indicate the possibility of using human hair as a fiber-shaped flexible substrate and will allow the use of hair-based hierarchical heterostructures as building blocks to create exciting opportunities for next-generation high-performance, multifunctional, lowcost, and flexible optoelectronic devices. KEYWORDS: UV photodetectors, fast photoresponse, optical-image sensors, photon-triggered logic gates, human hair
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The optoelectronic and mechanical performance of flexible optoelectronic devices greatly depends upon the flexible substrates that support the functional materials.22 Therefore, substrate selectivity is a crucial concern. Among all flexible substrates, fiber-shaped substrates such as carbon fibers,23−25 metal wires,26 cellulose nanofibers,27 and polycarbonate (PC)28 or carbon nanotubes29 are particularly attractive for
INTRODUCTION
Flexible and portable optoelectronic devices that can intelligently interact with humans have attracted a considerable amount of attention over the past few years due to the growing demand for modern consumer electronics.1−10 The development of flexible optoelectronic devices has expanded to a wide range of applications such as fundamental flexible photodetectors,11−13 displays,14 solar cells,15−17 optical logic gates,18 light-emitting diodes (LEDs),19,20 and optical-image sensors.21 Generally, flexible devices are produced through the direct growth or the transfer of nanomaterials on flexible substrates. © 2019 American Chemical Society
Received: April 28, 2019 Accepted: June 17, 2019 Published: June 17, 2019 24459
DOI: 10.1021/acsami.9b07423 ACS Appl. Mater. Interfaces 2019, 11, 24459−24467
Research Article
ACS Applied Materials & Interfaces smart textiles and wearable optoelectronics. They can be used to create various functional templates by growing different nanomaterials on the surface and can be weaved or integrated to form a variety of intelligent devices without sacrificing their optoelectronic performance.30 However, the current flexible substrates for commercial applications are either nonbiodegradable or costly, and thus, their production and disposal processes are expensive and environmentally hazardous. As a result, an alternative substrate, which is indispensable for the preparation of flexible devices, is vital and must urgently be explored for their cost-effective and environmentally friendly applications. Human hair, a renewable material from the human body and readily available as waste from barbershops, is a mechanically strong fiber with excellent flexibility. However, the potential of using hair as a substrate for flexible device fabrication remains largely unexplored.31−33 A human hair has a diameter of only several tens of micrometers and weighs very little. It can easily be tailored into different lengths via a simple cutting process. Moreover, hair is very stable in the atmosphere because it consists of hard keratins with a high sulfur content.31 Although it is biodegradable, the network structure composed of hydrogen bonds and disulfides makes it difficult to decompose.32 Additionally, it will be free from allergic reactions if the hair is implanted into the same human body because it is organic material that originated from self.33 Thus, using human hair as a substrate to fabricate a photosensitive hair-based heterostructure is significantly important and can lead to real breakthroughs in creating promising opportunities for flexible, portable/wearable, biocompatible, and inexpensive optoelectronic devices. However, the thermal liability and surface roughness of human hair present important engineering challenges to be faced before nanostructures can be added to it. A reasonable solution to these problems will make human hair attractive compared to conventional stiff and fiber-shaped substrates and can induce impressive progress beyond the limits of traditional electronic and optoelectronics strategies. ZnO nanorods (NRs) are excellent photoelectronic components that can be grown on arbitrary substrates [such as graphene, paper, polyethylene terephthalate (PET), glass, and semiconductors] through conventional seed-layer deposition combined with low-temperature growth processes.34−36 On one hand, the deposition of the ZnO seed layer using the magnetron sputtering method on a rough surface may offer a smoother surface and homogeneous epitaxial growth layers. On the other hand, low-temperature growth processes of ZnO NRs using hydrothermal methods (
