Elsevier

Solar Energy

Volume 188, August 2019, Pages 278-290
Solar Energy

Improved sensing behaviour of self-healable solar light photodetector based on core-shell type Ni0.2Zn0.8Fe2O4@ poly (Urea-Formaldehyde)

https://doi.org/10.1016/j.solener.2019.06.003Get rights and content

Highlights

  • A new way to use the self-healing materials in electronic devices.

  • Ultrafast response (1.74 sec) and recovery time (2.84 sec) of Ni0.2Zn0.8Fe2O4 thin film were observed.

  • 98.5% recovery of sensing properties was observed.

  • Very first self-healable ferrite based solar light photodetector with almost double responsivity (0.46 mW/A) was demonstrated.

Abstract

In this work, a bilayered ultra responsive self-healable photodetector that can restore both its structure as well as sensing property after deformation has been reported. This photodetector is based on ferrite with ultrafast sensing ability along with restoration property. In this dual-layered structure, the upper layer is Ni0.2Zn0.8Fe2O4 (NZF) prepared by citrate gel method and acts as sensing layer, whereas, the lower layer is Urea-Formaldehyde (U-F) microcapsules with flaxseed oil and NZF core. Here bottom layer acts as a healing layer, which can successfully restore film sensing property after deformation. Flaxseed oil acts as a medium to transport NZF from lower layer to the upper sensing area, which was deformed manually. The evaluated photoresponse and recovery time of NZF before deformation are 1.74 sec and 3.28 sec at 100 mW/cm2 respectively, whereas, response and recovery after healing were 1.75 sec and 2.84 sec respectively. The solar light photodetector based on microcapsule that can restore its sensing property ∼98.5%. The purpose of this work is to develop a method by which anyone can fabricate the different types of self-healable solar light photodetector.

Graphical abstract

Bilayered ultra-responsive self-healable photodetector with ∼98.5% recovery of sensing property, is fabricated using a very simple technique. Ultrafast response and recovery time along with self-healing nature give a new path to electronic devices.

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Introduction

Non-renewable energy resources like fossil fuel, coals etc. are going to deplete in the near future. The continuous increment in global population and socio-economics will lead to the consumption of more and more electricity (Destek and Aslan, 2017). Non-renewable energy alone cannot fulfil these electricity requirements and hence conventional energy resources will play a vital role in the near future. Electricity conservation is as important as electricity generation to gain sustainable growth. Various research groups continuously working on superconductors (Saito et al., 2016, Charnukha et al., 2018), batteries (Han et al., 2015, Song et al., 2015, Sun et al., 2017), light dependent resistors (LDR) (Rawal et al., 2015, Tripathi et al., 2018) in order to save the generated electric power. Most of the countries are wasting a huge amount of electric power due to unnecessarily overriding of lightning equipment during day time. The unfamiliarity of the energy saving policies and the high cost of automatic switches, like light dependent resistors (LDRs), seem to be the main reasons for electrical energy wastage (Rawal et al., 2016, Rawal et al., 2017). The solar light photodetector has a property to change their resistance with a variation of light intensity. Nanostructured metal oxides and metal sulphides are extensively explored for photoconductors and photo-conducting light switches (Kripal et al., 2011, Tripathi et al., 2015, Georgakopoulos et al., 2015), while ferrites are the least investigated materials for photodetector applications.

Other well-known problems in context to the serviceability of electronic devices e.g. photodetectors are continuous degradation of these devices by means of corrosion, repeated mechanical strain and damage during functioning. Even a slight change in a structural design by means of external cause leads to a gigantic change in output performance. In some cases, this causes the total failure of the whole device. These deformations in electronic devices lead to a tremendous increment in electronic waste (E-waste) year by year. Approximately, 44.7 million metric ton of e-waste was generated in 2016 and 47 million metric tons in 2017 (Baldé et al., 2017). Moreover, e-waste creates severe environmental and human health impacts. As these wastes contain heavy and toxic materials like Hg, Cd, Pb, etc. (ISWA, 2009), which contaminate groundwater and soil which directly or indirectly affects all living organisms (Leung et al., 2006, Zhang and Xu, 2016, Labunska et al., 2013). In recent years, research communities are trying to develop self-healable electronic devices, which can regenerate their structures and electrical properties after a mechanical failure. There is remarkable growth in the field of self-healable electronic devices like nanogenerators (Song and Li, 2014, World Energy Resources, 2016, Lee et al., 2015), perovskite solar cells (Xu et al., 2017, Parida et al., 2017, Zhao et al., 2016), sensing devices (Li et al., 2016, Lang et al., 2016, Jin et al., 2016, Yang et al., 2015), etc. Polymeric based self-healing materials are the key component in these devices.

In this work, we have addressed this issue to recover the sensing performance of solar light photodetectors after deformation. NZF-flaxseed oil core with U-F shell was prepared by using an oil emulsion method. The self-healing, as well as free-flowing capability of flaxseed oil, is well established in previous research articles (Lang and Zhou, 2017, Behzadnasab et al., 2014, Hasanzadeh et al., 2015, Szabó et al., 2015). The whole synthesis is very simple and was performed only using magnetic stirrer, which is a novelty of this process. We have demonstrated a photodetector device which can recover its sensing property after deformation in its structure. The schematic diagram of the self-healing mechanism is shown in Fig. 1. A bilayer self-healable device in which upper layer was Ni0.2Zn0.8Fe2O4 (NZF) nanostructure and lower layer consists of Urea-formaldehyde (U-F) microcapsule inside which same NZF nanoparticles were filled along with flaxseed oil. With the free-flowing capability of flaxseed oil, NZF nanoparticles from microcapsules get deposited in crack generated. Here flaxseed oil works as a transport medium, which transports NZF nanoparticles from the lower layer to the vacated region (crack). The self-healing, as well as free-flowing capability of flaxseed oil, is well established and reported in many reputed research articles (Lang and Zhou, 2017, Behzadnasab et al., 2014, Hasanzadeh et al., 2015, Szabó et al., 2015).

Section snippets

Materials

Nickel nitrate hexahydrate, zinc nitrate hexahydrate, iron nitrate nonahydrate, citric acid, distilled water and liquid ammonia were used for Ni0.2Zn0.8Fe2O4 (core) synthesis. Polyvinyl alcohol (PVA), urea, ammonium chloride, resorcinol, hydrochloric acid, extra pure flaxseed oil and formaldehyde (37 wt%) were used for microcapsule synthesis. All the chemicals except flaxseed oil were purchased from Fisher Scientific. Extra pure flaxseed oil was purchased from Sigma-Aldrich and all the

Characterizations

Surface morphologies of NZF, microcapsules and bilayered film were analyzed using scanning electron microscope (SEM; JEOL JSM-6490 LV). Self-healing performance of fabricated bilayer film was also investigated using SEM. Encapsulation of NZF nanoparticles inside U-F microcapsules was confirmed by high-resolution transmission electron microscope analysis (HR-TEM; Tecnai G2 F30 STWIN) along with selected area electron diffraction (SAED) pattern. The composition, phase identification and purity of

Results and discussion

Ni0.2Zn0.8Fe2O4 nanopowder was synthesized by citrate gel method. The citrate process is a robust method as it is easy, simple, and it doesn’t involve any decorative and expensive experimental setup. The main advantages of this method are:

  • (a)

    The capability of producing a homogenous mixture of the constituent ions.

  • (b)

    As the ignition is involved in the process, there is a faint chance of contamination of materials.

  • (c)

    The method is simple enough providing less energy consumption and saving in time.

  • (d)

    The

Conclusions

In summary, we successfully demonstrated a method to synthesize and fabricate a bilayered photo sensing device that can regain its original functionality after defect takes place in its structure. The NZF nanoparticles synthesized via citrate gel method was served as the sensing material. The U-F microcapsules with flaxseed oil and NZF core were synthesized by oil emulsion technique, which works as a self-healing material. The synthesis process is very simple as it uses only magnetic stirrer

Acknowledgements

Shakti Singh and Abhisikta Bhaduri are highly thankful to Babasaheb Bhimrao Ambedkar University, Lucknow for UGC fellowship. National Physical Laboratory (NPL), New Delhi is gratefully acknowledged for providing HR-TEM facility.

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