Increasing Photostability of Inverted Nonfullerene Organic Solar Cells by using Fullerene Derivative Additives

Marcella Günther, Dominic Blätte, Anna Lena Oechsle, Sergio Sánchez Rivas, Yousefi Amin Amir Abbas , Peter Müller-Buschbaum, Thomas Bein, Tayebeh Ameri

Research output: Contribution to journalArticlepeer-review

Abstract

Organic solar cells recently achieved efficiencies of over 18% and are well on their way to practical applications, but still considerable stability issues need to be overcome. One major problem emerges from the electron transport material zinc oxide (ZnO), which is mainly used in the inverted device architecture and decomposes many high performance nonfullerene acceptors due to its photocatalytic activity. In this work we add three different fullerene derivatives – PC71BM, ICMA and BisPCBM – to an inverted binary PBDB-TF:IT-4F system in order to suppress the photocatalytic degradation of IT-4F on ZnO via the radical scavenging abilities of the fullerenes. We demonstrate that the addition of 5% fullerene not only increases the performance of the binary PBDB-TF:IT-4F system, but also significantly improves the device lifetime under UV illumination in inert atmosphere. While the binary devices lose 20% of their initial efficiency after only 3 hours, this time is increased fivefold for the most promising ternary devices with ICMA. We attribute this improvement to a reduced photocatalytic decomposition of IT-4F in the ternary system, which results in a decreased recombination. We propose that the added fullerenes protect the IT-4F by acting as a sacrificial reagent, and thereby suppress the trap state formation. Furthermore, we show that the protective effect of the most promising fullerene ICMA is transferable to two other binary systems PBDB-TF:BTP-4F and PTB7-Th:IT-4F. Importantly, this effect can also increase the air stability of PBDB-TF:IT-4F. This work demonstrates that the addition of fullerene derivatives is a transferable and straightforward strategy to improve the stability of organic solar cells.
Original languageEnglish
Pages (from-to)19072–19084
JournalACS Applied Materials & Interfaces
Volume13
Issue number16
Early online date16 Apr 2021
DOIs
Publication statusPublished - 28 Apr 2021

Keywords

  • ternary organic solar cells
  • photostability
  • zinc oxide
  • nonfullerene acceptors
  • Fullerenes
  • photocatalytic activity

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