Transparency, moisture barrier property, and performance of the alternative solar cell encapsulants based on PU/PVDC blend reinforced with different types of cellulose nanocrystals

Kitti Yuwawech,Supachok Tanpichai,Jatuphorn Wootthikanokkhan

doi:10.1007/s40243-018-0128-6

Abstract

Two different types of cellulose nanocrystals, derived from water hyacinth fibers and microfibrillated cellulose (MFC), were prepared using an acid hydrolysis treatment. These cellulose nanocrystals (CNCs) were further used as barrier enhancing fillers for polyurethane (PU) blended with 25 wt% of poly(vinylidene dichloride) (PVDC). The aim of this study was to investigate the effects of types and concentration of CNCs on mechanical, optical and barrier properties of polymer composite films. The feasibility of applying the obtained composite films as an encapsulating material for enhancing the lifetime of dye sensitized solar cells (DSSC) was also of interest. The acid hydrolysis of the MFC-yielded rod-shaped cellulose nanocrystals (CNCm) while the acid-hydrolyzed water hyacinth led to a formation of spherical-shaped cellulose nanocrystals (CNCw). Regardless of the types of CNCs, the optical transparency of the composite films was maintained well above 60%. According to results in this study, the most efficient film with the lowest water vapor transmission rate of 0.0517 g m−2 day−1 was the PU/PVDC film reinforced with 0.1 wt% of CNCm. The encapsulants made from this composite could prolong the lifetime of the DSSC devices for up to 14 days, with the normalized PCE value of 0.78. Overall, this work showed that the considerations of the barrier properties of the polymer encapsulants alone are insufficient to ensure that the system would be effective. An interfacial adhesion between the encapsulants and the electrodes, as well as some side reactions between polymers and chemicals inside the fabricated cell, should also be taken into account.

Highlights

IntroductionOn the basis of the types of photoactive materials and their fabrication technology, photovoltaic cells can be classified into three main categories: the silicon-based technology, the compound semiconductor-based technology (such as CIGS and CdTe), and the new emerging solar cells technology
On the basis of the types of photoactive materials and their fabrication technology, photovoltaic cells can be classified into three main categories: the silicon-based technology, the compound semiconductor-based technology, and the new emerging solar cells technology
This work demonstrated that the moisture barrier property of PU/poly(vinylidene dichloride) (PVDC) film (75/25%w/w) can be improved by adding a suitable amount of cellulose nanocrystals (CNCs) into the polymers matrix

Summary

Introduction

On the basis of the types of photoactive materials and their fabrication technology, photovoltaic cells can be classified into three main categories: the silicon-based technology, the compound semiconductor-based technology (such as CIGS and CdTe), and the new emerging solar cells technology. (3) the use of the polymer barrier film for lamination and encapsulation. It should be noted that this thermosetting polymer is a kind of UV curable epoxy-based resin. This was originally designed and developed for use with the OPV and not for the DSSC. This is an important issue since both the DSSC dye and the electrolyte are susceptible to photocatalytic attack, and so they can be degraded upon an exposure to UV light during the encapsulation process [6]. The development of high performance encapsulants for various types of solar cells is still interesting and deserves consideration

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