Recently, researchers from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences (CAS) and the Dalian University of Technology (DUT) revealed the tunneling effects in the active layer of organic solar cells (OSCs) by fabricating BHJ and layer-by-layer devices with five different poly(aryl ether)s (PAEs). 

The proposed tunneling effects and PAE matrices strategy have important implications for fabricating efficient, stable, and flexible organic devices. 

The related findings were published in Cell Reports Physical Science on April 19. 

In tunneling effects, electrons and holes freely flow across the insulating barriers. For organic solar cells (OSCs), tunneling effects are one of the most basic theories that have long been overlooked in the bulk-heterojunction (BHJ) layers. 

Some studies have mentioned that small amounts of solid-state polymer additives can partially improve the efficiency, stability, or flexibility of OSCs. However, the role of insulating polymers in the active layer of OSCs and the question of how to design the structure of insulating polymers for promoting device performance efficiently remain unclear. 

With rational molecular design, the researchers demonstrated that heat-resistant PAE matrices with high stretchability could improve the efficiency, stability, and mechanical flexibility of OSCs. 

Furthermore, given the tunneling effect in OSCs, they speculated that it may also exist in other organic semiconductor blends. The excellent thermal stability and mechanical property of PAE resins make an unexpected and significant contribution to promoting the stability and flexibility of OSCs. 

The proposed tunneling effect and PAE matrices strategy show that insulating polymers can play a key role in organic devices and also suggest a new design principle for promoting OSCs toward practical applications. 

The research was supported by Youth Innovation Promotion Association of CAS, National Natural Science Foundation of China, and Shandong Provincial Natural Science Foundation. 

Tunneling effects in bulk-heterojunction organic solar cells (Image by HAN Jianhua)