Rod-Coil Block Copolymer: Fullerene Blend Water-Processable Nanoparticles: How Molecular Structure Addresses Morphology and Efficiency in NP-OPVs.

Anna Maria Ferretti,Tersilla Virgili,Ivana Moggio,Silvia Destri,Stefania Zappia,Marianna Diterlizzi,Lucia Ganzer,Guido Scavia,William Porzio,Varun Vohra,Umberto Giovanella,Eduardo Arias

doi:10.3390/nano12010084

Anna Maria Ferretti, Tersilla Virgili + Show 10 more

Open Access

https://doi.org/10.3390/nano12010084

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Abstract

The use of water-processable nanoparticles (WPNPs) is an emerging strategy for the processing of organic semiconducting materials into aqueous medium, dramatically reducing the use of chlorinated solvents and enabling the control of the nanomorphology in OPV active layers. We studied amphiphilic rod-coil block copolymers (BCPs) with a different chemical structure and length of the hydrophilic coil blocks. Using the BCPs blended with a fullerene acceptor material, we fabricated NP-OPV devices with a sustainable approach. The goal of this work is to clarify how the morphology of the nanodomains of the two active materials is addressed by the hydrophilic coil molecular structures, and in turn how the design of the materials affects the device performances. Exploiting a peculiar application of TEM, EFTEM microscopy on WPNPs, with the contribution of AFM and spectroscopic techniques, we correlate the coil structure with the device performances, demonstrating the pivotal influence of the chemical design over material properties. BCP5, bearing a coil block of five repeating units of 4-vinilpyridine (4VP), leads to working devices with efficiency comparable to the solution-processed ones for the multiple PCBM-rich cores morphology displayed by the blend WPNPs. Otherwise, BCP2 and BCP15, with 2 and 15 repeating units of 4VP, respectively, show a single large PCBM-rich core; the insertion of styrene units into the coil block of BCP100 is detrimental for the device efficiency, even if it produces an intermixed structure.

Highlights

We studied the blend water-processable nanoparticles (bWPNPs) morphology by means of atomic force microscopy (AFM), transmission electron microscopy (TEM), and energy filtered TEM (EFTEM), to clarify how the morphology of the nanodomains is related to the features of the different coil molecular structures in the block copolymers (BCPs), and how they led to different device performances
We investigated the morphology of the water-processable nanoparticles (WPNPs) at the nanoscale level, to demonstrate if there is a relationship between the material chemical structure and the formation of suitable donor/acceptor domains inside the bWPNPs, as observed in the case of BCP5 bWPNPs
The BCPs were used for the preparation of blend water-processable nanoparticles with phenyl-C61-butyric acid methyl ester (PCBM) as the acceptor material through an adapted miniemulsion approach, without using any other surfactants

Summary

Introduction

In the last few decades, organic photovoltaics (OPVs) have attracted considerable interest as a promising alternative energy source, especially considering the capability of this technology to produce lightweight, flexible, and semitransparent devices using solution-processable coating and printing processing for large-scale production [1]. Nanomaterials 2022, 12, 84 development [5]. OPV fabrication involves the use of large amounts of chlorinated organic solvents (e.g., chloroform, chlorobenzene, dichlorobenzene, etc.) on the laboratory scale in order to obtain effective active layer morphology with an optimized interpenetrating network between donor and acceptor materials [8]. The ideal industrial production should be highly sustainable, reducing the environmental impact and the manufacturing cost of the devices [9,10]

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