LIMNO develops a new hybrid system for solar energy conversion

In general, the exfoliated transition metal dichalcogenides (2D-TMDs) are attractive light-harvesting materials for large-area and inexpensive solar energy conversion given their ability to form highly tolerant heterojunctions. However, the preparation of large-area heterojunctions with these materials remains a challenge toward practical devices, and the details of photogenerated charge carrier harvesting are not well established. In this paper, lead author Xiaoyun Yu reports an all solution-based method to prepare large-area hybrid heterojunction films consisting of exfoliated semiconducting 2H-MoS₂ flakes and a perylene-diimide (PDI) derivative. Hybrid photoelectrodes exhibited a 6-fold improvement in photocurrent compared to that of bare MoS₂ or PDI films. Kelvin probe force microscopy, X-ray photoelectron spectroscopy, and transient absorption measurements (with the help of Prof. Natalie Banerji and her team from University of Fribourg) of the hybrid films indicate the formation of an interfacial dipole at the MoS₂/organic interface and suggest that the photogenerated holes transfer from MoS₂ to the PDI. Moreover, performing the same analysis on MoSe₂-based hybrid devices confirms the importance of proper valence band alignment for efficient charge transfer and photogenerated carrier collection in TMD/organic semiconductor hybrid heterojunctions. Overall, the continued development of TMD–organic hybrid heterojunction-based devices, together with our demonstration of the facile solution-based processing, will make these hybrid systems promising for global-scale solar energy conversion.