Elucidate the Thermal Degradation Mechanism of Y6‐Based Organic Solar Cells by Establishing Structure‐Property Correlation

Organic solar cells (OSCs) achieved performance booming benefiting from the emerging of non‐fullerene acceptors, while inadequate device stability hampers their further application. At present, the prevalent belief attributes the inevitable thermal degradation of OSC device to morphological instabil...

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Bibliographic Details
Published in:Advanced energy materials 2024-08, Vol.14 (30), p.n/a
Main Authors: Xin, Jingming, Zhao, Chao, Geng, Ziqi, Xue, Wenyue, Chen, Zhenyu, Song, Chunpeng, Yan, Han, Liang, Qiuju, Miao, Zongcheng, Ma, Wei, Liu, Jiangang
Format: Article
Language:English
Subjects:
Crystallization
Devices
Electron mobility
Energy levels
molecular orientation
Morphology
non‐fullerene acceptor
organic solar cells
Performance degradation
Phase separation
Photoelectric effect
Photoelectricity
Photovoltaic cells
Solar cells
Stability
Thermal degradation
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Summary:Organic solar cells (OSCs) achieved performance booming benefiting from the emerging of non‐fullerene acceptors, while inadequate device stability hampers their further application. At present, the prevalent belief attributes the inevitable thermal degradation of OSC device to morphological instability caused by excessive phase separation and crystallization in the active layer during device operation. However, it is inapplicable for state‐of‐art Y6‐based devices which strongly degrade before large‐scale morphology change. Herein, an alternative degradation mechanism is elucidated wherein molecular orientation change and demixing induced performance degradation in Y6‐based devices. Distinct from IT‐4F‐based counterpart, Y6‐based devices suffer severe thermal degradation dominated by open‐circuit voltage (VOC) and fill factor (FF) losses. The VOC loss is attributed to molecular orientation transition of polymer donors from edge‐on to face‐on, leading to a strong built‐in potential reduction and increase in non‐radiative loss due to energy level shifting. As for FF decay, discontinuous acceptor phases result in electron mobility decrease by over orders of magnitude, originating from the increased molecular stacking and phase separation. This work reveals the thermal degradation mechanism for Y6‐based devices and correlates the photoelectric properties with morphology instability, which will offer guidance for improving the stability of high‐performance OSCs. In this work, polymer:Y6 organic solar cells are found prominent thermal degradation dominated by open‐circuit voltage (VOC) and fill factor (FF) losses. The underlying mechanism is elucidated that the polymer orientation transition from edge‐on to face‐on induces VOC decay, while demixing and aggregation intercept electron transportation leading to FF loss.
ISSN:1614-6832
1614-6840
DOI:10.1002/aenm.202401433