Understanding organic solar cells degradation process
|Due to their light weight, low cost and easy processability, organic solar cells (OSCs) are among the most promising photovoltaic technologies in terms of performance and possible application. However, their poor stability, especially attribute to intrinsic degradation processes, remains a significant limitation factor for their usage.
To address this, Dr Xinyu Jiang, Prof Peter Müller-Buschbaum and colleagues of the Technical University of Munich conducted a series of operando experiments at the Small Angle X-ray Scattering (SAXS) beamline at the CERIC Austrian partner facility in Elettra Sincrotrone Trieste. The focus was on analyzing the temporal evolution of the morphology of different OSCs active layers, which contain four different acceptors blended with a conjugated polymer donor that differ in the degree of π–π stacking (attractive, noncovalent orbital overlap between the pi bonds of adjacent aromatic rings) in crystallinity.
Researchers discovered that, following the operation of the device, the active layer for all types of devices undergoes a transformation, and develops a finer structure with more isolated domains. Moreover, the morphology of the middle-sized domains shows stronger changes during the initial operating stage of OSCs that have layers with relatively poor π–π stacking. This results in a more pronounced performance decay of these devices. Notable, the stability of the active layer morphology was more affected in well-intermixed donor–acceptor systems with notable face-on crystallinity compared to slightly de-mixed donor–acceptor systems with good π–π stacking.
These outcomes will help to develop stronger and more effective organic solar cells by acting on the structure of their active layers, enabling applications in both the sustainable energy and aerospace sectors.
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