Alternative heterojunction architecture improves organic photodetector performance

Organic photodetectors rely on heterojunctions, but traditional heterojunction structures suffer from issues like bimolecular recombination losses and disrupted charge transport. Gong et al. developed an alternative approach termed interpenetrated heterojunctions, or IPHJs, that combine the advantages of older architectures such as bulk heterojunctions and planar heterojunctions.

The idea for IPHJs came from an unexpected observation that a polymer N2200 creates a porous surface when deposited onto a polydimethylsiloxane substrate. By transferring a PM6 semiconductor onto the porous N2200 layer and annealing to enable the PM6 to fill the pores, the researchers created a heterojunction that integrates a planar interface with bulk-like intermixed structures at the pores.

“What began as an accidental discovery turned into a robust and general method for building new device architectures,” said author Yuanyuan Hu.

The researchers used imaging and spectroscopy to measure the performance of the IPHJ in photodiodes and phototransistors. The results showed the photodiodes had exceptional state-of-the-art performance with high responsivity.

“These breakthroughs suggest that IPHJs can fundamentally change the landscape for organic optoelectronics and may be widely extendable to other device types, opening up fresh opportunities for both research and applications,” Hu said. “In particular, the IPHJ strategy could inspire innovations in organic solar cells, improving both charge separation and extraction.”

Next, the researchers plan to continue exploring different material combinations for creating semiconductors with the goal of optimizing the porous layer formation and fine turning device properties through doping strategies. They also hope to collaborate with other groups to integrate the IPHJs into organic photovoltaic devices.

Source: “Achieving high-performance organic photodetectors with novel interpenetrated heterojunction architectures,” by Zhenqi Gong, Yiwei Zhang, Ping-An Chen, Zhaojing Xiao, Kaixin Niu, Jiangnan Xia, Huan Wei, Jiaqi Ding, Yu Zhang, Chengyuan Peng, Xi Zeng, Wenpei Shi, Chen Chen and Yuanyuan Hu, Applied Physics Reviews (2025). The article can be accessed at https://doi.org/10.1063/5.0273823 .