Stepwise heating in Stille polycondensation toward no batch-to-batch variations in polymer solar cell performance

Sang Myeon Lee,Kwang Hyun Park,Changduk Yang,Seungon Jung,Hyesung Park

doi:10.1038/s41467-018-03718-7

Sang Myeon Lee, Kwang Hyun Park + Show 3 more

Open Access

https://doi.org/10.1038/s41467-018-03718-7

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Abstract

For a given π-conjugated polymer, the batch-to-batch variations in molecular weight (Mw) and polydispersity index (Ð) can lead to inconsistent process-dependent material properties and consequent performance variations in the device application. Using a stepwise-heating protocol in the Stille polycondensation in conjunction with optimized processing, we obtained an ultrahigh-quality PTB7 polymer having high Mw and very narrow Ð. The resulting ultrahigh-quality polymer-based solar cells demonstrate up to 9.97% power conversion efficiencies (PCEs), which is over 24% enhancement from the control devices fabricated with commercially available PTB7. Moreover, we observe almost negligible batch-to-batch variations in the overall PCE values from ultrahigh-quality polymer-based devices. The proposed stepwise polymerization demonstrates a facile and effective strategy for synthesizing high-quality semiconducting polymers that can significantly improve device yield in polymer-based solar cells, an important factor for the commercialization of organic solar cells, by mitigating device-to-device variations.

Highlights

For a given π-conjugated polymer, the batch-to-batch variations in molecular weight (Mw) and polydispersity index (Ð) can lead to inconsistent process-dependent material properties and consequent performance variations in the device application
Electrochemical, and morphological properties between the stepwise protocol-derived and commercially available PTB7 polymers, the resulting ultrahigh-quality polymer-based solar cells exhibit superior power conversion efficiencies (PCEs) of up to 9.97% with impressively negligible device-to-device performance variations, constituting a substantial improvement from control devices based on the commercial polymer
We evaluated the Mw and Ð values by high-temperature gel permeation chromatograph (GPC) at 120 °C using 1,2,4-tricholorobenzene as the eluent

Summary

Introduction

For a given π-conjugated polymer, the batch-to-batch variations in molecular weight (Mw) and polydispersity index (Ð) can lead to inconsistent process-dependent material properties and consequent performance variations in the device application. Using a stepwise-heating protocol in the Stille polycondensation in conjunction with optimized processing, we obtained an ultrahigh-quality PTB7 polymer having high Mw and very narrow Ð. The resulting ultrahigh-quality polymer-based solar cells demonstrate up to 9.97% power conversion efficiencies (PCEs), which is over 24% enhancement from the control devices fabricated with commercially available PTB7. We observe almost negligible batch-to-batch variations in the overall PCE values from ultrahigh-quality polymer-based devices. Electrochemical, and morphological properties between the stepwise protocol-derived and commercially available PTB7 polymers, the resulting ultrahigh-quality polymer-based solar cells exhibit superior PCEs of up to 9.97% with impressively negligible device-to-device performance variations, constituting a substantial improvement from control devices based on the commercial polymer. The stepwise Stille polycondensation process is readily adoptable to a wide range of general π-conjugated polymers requiring ultrahigh quality and can be immediately incorporated into synthetic organic chemists’ repertoire as a principal reaction protocol

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Conclusion