Angew. Chem.: A binary organic solar cell based on selenophene-fused perylene imidide cathode interface material to achieve 19% efficiency through facilitated charge extraction
Organic solar cells have attracted much attention because of their advantages of light weight, flexibility, and roll-to-roll preparation. With the development of new materials and the optimization of device technology, the energy conversion efficiency of single-cell organic solar cells has exceeded 19%. Due to the typical sandwich structure (anode/active layer/cathode) of organic solar cells, the interface material is very critical for the extraction of charge from the active layer to the electrode, and the current research on simple and effective interface materials is relatively insufficient. To this end, the team of the National Center for Nanoscience and Technology has designed and synthesized a perylene dimidimine cathode interface material based on selenophene fused to achieve high-efficiency binary organic solar cells.
According to the density functional theory calculation, SePDI3 after selenophene fused has better rigidity and planarity. By ultraviolet absorption spectroscopy, electron paramagnetic resonance, conductivity tests show that SePDI3 has better self-doping characteristics and higher conductivity. Ultraviolet photoelectron spectroscopy showed that SePDI3 also had good electrode function function modification ability. Various analyses have shown that SePDI3 has the potential to be used as a cathode interface material for organic solar cells.
The results show that the contact between SePDI3 and PM6 can produce a photovoltaic effect, and then the charge transfer occurs at the PM6/SePDI3 interface. In addition, SePDI3 devices have a larger built-in potential and a smaller transmission resistance, which can avoid excessive accumulation of electrons at the interface and accelerate electron transfer. Transient photovoltage/photocurrent measurements also show that the SePDI3 device has faster charge extraction and lower charge recombination behavior.
More importantly, the interaction between the conjugated backbone and Se atoms can enhance spin-orbit coupling and promote interstitial crossing, resulting in the formation of reactive oxygen species in SePDI3, which promotes the chemical interaction between SePDI3 and L8-BO, forms additional electron transport channels, and facilitates electron extraction. In addition, the KPFM results also showed that the introduction of SePDI3 was conducive to the extraction of electrons from the active layer. Improved charge extraction helps the device to increase both the short-circuit current density and the fill factor. Finally, the organic solar cells with PM6:L8-BO as the active layer and SePDI3 as the cathode interface layer achieved an efficiency of 19.04% and a high fill factor of 81.65%.
Thesis information
Selenophene-fused Perylene Diimide-based Cathode Interlayer Enables 19% Efficiency Binary Organic Solar Cells via Stimulative Charge Extraction
Zongtao Wang, Helin Wang, Lei Yang, Mengzhen Du, Lei Gao, Qiang Guo, Erjun Zhou
The first author of the article is Wang Zongtao, a doctoral student jointly trained by Zhengzhou University and National Center for Nanoscience, and the corresponding authors are researcher Zhou Erjun and associate researcher Wang Helin of National Center for Nanoscience and Technology.