Biobased Cellulosic–CuInS2 Nanocomposites for Optoelectronic Applications

David Reishofer,Thomas Rath,Harald Plank,Heinz Amenitsch,Stefan Spirk,Sebastian Dunst,Heike M Ehmann,Bruno Alonso,Gregor Trimmel,Christian Gspan,Emmanuel Belamie

doi:10.1021/acssuschemeng.6b02871

Abstract

A generic approach to design optoelectronic devices using renewable biopolymers is demonstrated. As a proof of principle, a biopolymer/CuInS2 nanocomponent-based solar cell has been assembled by using a cellulose derivative with a reasonable life cycle performance, namely, trimethylsilyl cellulose (TMSC). The solar cells are manufactured using a mixture of copper and indium xanthates as precursors, which decompose and form CIS nanoparticles within the biopolymer matrix during a thermal treatment, which was investigated by in situ combined grazing incidence small and wide-angle X-ray scattering experiments. The growth of the nanoparticles is thereby controlled by the TMSC matrix. The nanocrystals exhibit an average diameter of approximately 4 nm. Using this composite, it was possible to fabricate solar cells, generating current in a wide range of the solar spectrum and exhibiting power conversion efficiencies of ca. 1%.

Highlights

To meet the challenges of climate change and sustainable use of global resources, tremendous efforts have been made to replace fossil derived energy resources and synthetic petrochemicalbased materials by those derived from renewable resources
As a proof of principle, a biopolymer/CuInS2 nanocomponent-based solar cell has been assembled by using a cellulose derivative with a reasonable life cycle performance, namely trimethylsilyl cellulose (TMSC)
Metal xanthates have proven to be most efficient since they decompose accompanied by the formation of only volatile by-products leaving the layer leading to pure conjugated polymer/nanocrystal nanocomposite thin films which can be directly applied as absorber layers in solar cells.[12,13,14]

Summary

Introduction

To meet the challenges of climate change and sustainable use of global resources, tremendous efforts have been made to replace fossil derived energy resources and synthetic petrochemicalbased materials by those derived from renewable resources. One currently followed research area is the use of nanocrystals and nanocomposites in solar cells using at present mainly toxic compounds such as PbS or Cd-based chalcogenides.[2,3,4,5] In order to overcome environmental concerns, alternatives have been thoroughly investigated, among which CuInS2 represents a non-toxic alternative.[6,7,8,9] in this case, CuInS2 is usually synthesized via wet-chemical/colloidal synthesis routes employing long-chained capping ligands, which have to be removed or exchanged using potentially toxic reagents (e.g. 1,3-benzenedithiol, hexanethiol, etc.) before the nanocrystalline absorber films for the solar cells can be prepared.[10,11] A convenient way to avoid capping agents and ligand exchange reagents is to generate the metal sulfide particles directly in the photovoltaic active layer. Metal xanthates have proven to be most efficient since they decompose accompanied by the formation of only volatile by-products leaving the layer leading to pure conjugated polymer/nanocrystal nanocomposite thin films which can be directly applied as absorber layers in solar cells.[12,13,14] In this work, we investigate if it is possible to fully circumvent the use of synthetic capping ligands, ligand exchange reagents and polymers in the fabrication of CuInS2-based nanocrystal solar cells by replacing them in the in-situ route by the bio-based trimethylsilyl cellulose

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