A novel strategy to improve the operational and outdoor stability of non-fullerene acceptor-based organic solar cells
Aren Yazmaciyan a, Han Xu a, Sri Harish Kumar Paleti a, Maxime Babics a, Stefaan De Wolf a, Derya Baran a
a KAUST Solar Center (KSC), Physical Sciences and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
nanoGe Fall Meeting
Proceedings of Materials for Sustainable Development Conference (MAT-SUS) (NFM22)
#STAPOS - Stability of perovskite and organic solar cells
Barcelona, Spain, 2022 October 24th - 28th
Organizers: Carsten Deibel and Qiong Wang
Contributed talk, Aren Yazmaciyan, presentation 113
DOI: https://doi.org/10.29363/nanoge.nfm.2022.113
Publication date: 11th July 2022

Humankind is living in a climate emergency that requires immediate action. However, in the meantime, the world’s energy demand is continuously increasing; thus, making clean energy generation of paramount importance. Photovoltaics is at the forefront of this clean energy movement with organic photovoltaics emerging as a promising candidate to address this issue and meet this demand. Having said that, organic semiconductors came a long way from fullerene-based solar cells to state-of-the-art non-fullerene acceptor-based (NFAs) cells that show promise as next-generation photovoltaic devices. Organic solar cells employing such materials have already surpassed 20% in power conversion efficiencies (PCEs) after less than a decade of research, excluding initial attempts to outclass their fullerene counterparts in the 90s.[1] Much is done to realize high PCEs by the research community; nonetheless, the urgency to unravel the underlying mechanisms crippling the stability of the photovoltaic devices based on such material systems picked up only in recent years.

Even so, a thorough understanding or a guideline is still lacking to tackle this limitation once and for all. In this work, we implement a novel strategy, which we refer to as donor dilution, to improve the operational and outdoor stability of NFA-based systems in an archetypal donor:acceptor blend, namely, PTB7-Th:IEICO-4F.[2,3] Organic solar cells exploiting this material system with decreasing polymer content in the polymer:small molecule blend progressively perform superior both in operational and outdoor stability tests. Unencapsulated donor-diluted devices retain 85% of their initial PCE under continuous 1 sun equivalent metal halide lamp illumination at 40⁰C after 1000 hours. Furthermore, the in-house developed encapsulation procedure enables these devices to endure the harsh outdoor conditions (~23⁰C and ~64% relative humidity on average throughout winter) for an extended period in the Kingdom of Saudi Arabia.

These findings underpin the universal effort to improve the organic photovoltaic device stability, provide a practical strategy as a proof-of-concept to enhance the lifetime of organic photovoltaic devices, and bring this technology a step closer to commercialization. Future work consists of further examination of the universality of the donor dilution approach and is underway by testing various donor:acceptor blends with different classes of non-fullerene acceptors, such as state-of-the-art Y-series molecules.

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