New strategy developed for flexible organic solar cells with high efficiency and mechanical robustness

Prof. Ge Ziyi and their research team at the Ningbo Institute of Materials Technology and Engineering (NIMTE) within the Chinese Academy of Sciences have achieved a significant breakthrough in flexible organic solar cells (OSCs). They incorporated a ductile oligomeric acceptor (DOA) into the polymer donors and small molecule acceptors (PD:SMA) system, resulting in OSCs that offer both high power conversion efficiency (PCE) and mechanical durability. Their research findings have been published in the prestigious journal Advanced Materials.

OSCs have gained recognition as excellent candidates for flexible power sources due to their lightweight nature, flexibility, and ease of processing. As the market for wearable electronic devices continues to grow, the importance of high PCE and mechanical robustness in the development of wearable OSC applications becomes increasingly evident. However, flexible OSCs have traditionally struggled with relatively low PCEs (approximately 17%) and limited mechanical resilience compared to their rigid counterparts.

To address these challenges, the researchers introduced an innovative approach by adding a DOA as a third component to the PD:SMA blend system of OSCs. They synthesized three different DOAs, each with unique flexible bridging chain segments and molecular chain lengths – DOY-C2, DOY-C4, and TOY-C4.

The team conducted a comprehensive analysis of the photophysical, mechanical, and photovoltaic properties of OSCs with these different DOAs, specifically focusing on D18:N3. The incorporation of DOY-C4 into the D18:N3 system played a pivotal role in enhancing PCE for both rigid and flexible OSCs. This enhancement can be attributed to a significant reduction in voltage losses within the devices.

Furthermore, the flexible OSCs based on the D18:N3:DOY-C4 combination achieved an outstanding PCE of 17.91%, ranking among the highest values reported to date for flexible OSCs. Notably, these OSCs also displayed excellent mechanical robustness, with a crack-onset strain (COS) of 11.7%. This represents a remarkable 50% increase in COS when compared to devices based solely on D18:N3.

Even after subjecting the developed flexible OSCs to 2,000 consecutive bending cycles, they retained an impressive 98% of their initial PCE, demonstrating exceptional mechanical stability.

In summary, this study presents a promising and straightforward method for creating stable ternary OSCs that combine high efficiency and mechanical resilience, paving the way for the advancement of flexible solar energy technology.

Source: Chinese Academy of Sciences

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