The Influence of Conjugated Polymer Side Chain Manipulation on the Efficiency and Stability of Polymer Solar Cells.

Ilona Heckler,Morten Madsen,Maxime Defour,Jurgen Kesters,Huguette Penxten,Bruno Van Mele,Wouter Maes,Eva Bundgaard,Jan D’Haen

doi:10.3390/ma9030181

Ilona Heckler, Morten Madsen + Show 7 more

Open Access

https://doi.org/10.3390/ma9030181

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Abstract

The stability of polymer solar cells (PSCs) can be influenced by the introduction of particular moieties on the conjugated polymer side chains. In this study, two series of donor-acceptor copolymers, based on bis(thienyl)dialkoxybenzene donor and benzo[c][1,2,5]thiadiazole (BT) or thiazolo[5,4-d]thiazole (TzTz) acceptor units, were selected toward effective device scalability by roll-coating. The influence of the partial exchange (5% or 10%) of the solubilizing 2-hexyldecyloxy by alternative 2-phenylethoxy groups on efficiency and stability was investigated. With an increasing 2-phenylethoxy ratio, a decrease in solar cell efficiency was observed for the BT-based series, whereas the efficiencies for the devices based on the TzTz polymers remained approximately the same. The photochemical degradation rate for PSCs based on the TzTz polymers decreased with an increasing 2-phenylethoxy ratio. Lifetime studies under constant sun irradiance showed a diminishing initial degradation rate for the BT-based devices upon including the alternative side chains, whereas the (more stable) TzTz-based devices degraded at a faster rate from the start of the experiment upon partly exchanging the side chains. No clear trends in the degradation behavior, linked to the copolymer structural changes, could be established at this point, evidencing the complex interplay of events determining PSCs’ lifetime.

Highlights

Polymer solar cells (PSCs) have emerged as strong competitors in the field of renewable energy over the past two decades
Four new donor-acceptor-type low bandgap copolymers were successfully synthesized by manipulation of the side chains of two copolymers (P1 and P2) based on benzo[c][1,2,5]thiadiazole (BT) and thiazolo[5,4-d]thiazole (TzTz) acceptor units, respectively
The polymers were applied in polymer solar cells (PSCs) via roll-coating (RC) and spin-coating (SC)

Summary

Introduction

Polymer solar cells (PSCs) have emerged as strong competitors in the field of renewable energy over the past two decades. Judicious efforts on chemical engineering of the polymer (electron donor) materials, optimization of the solar cell architecture and the acquisition of additional fundamental insights on device operation have driven the power conversion efficiencies (PCEs) of this technology to levels approaching and even surpassing the 10% threshold [6,7,8]. 1),Figure require processing procedures (inert atmosphere, high temperature, etc.) and. 4,6‐diyl}; 1),rigorous require rigorous processing procedures (inert atmosphere, high temperature, etc.). Have so far only been successful on small laboratory-scale spin-coated (SC) devices [9]. For PSCstotobecome becomeeconomically economically viable, large-scale production techniques as roll-coating for PSCs viable, large‐scale production techniques (such(such as roll‐coating (RC))

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