有機太陽電池のエネルギー損失と界面を関連付けることで、太陽電池の効率が大幅に向上する可能性(Linking Energy Loss to Interfaces in Organic Solar Cells Could Make Them Much More Efficient)

2024-10-30 ノースカロライナ州立大学(NCState)

＜関連情報＞

• https://news.ncsu.edu/2024/10/interfaces-in-organic-solar-cells/
• https://www.cell.com/matter/abstract/S2590-2385(24)00534-4

有機太陽電池の界面エネルギーランドスケープをマッピングすることで、非放射損失低減の道筋が明らかになる Mapping the interfacial energetic landscape in organic solar cells reveals pathways to reducing non-radiative losses

Gaurab J. Thapa∙ Mihirsinh Chauhan∙ Jacob P. Mauthe∙ Daniel B. Dougherty∙ Aram Amassian
Matter  Published:October 30, 2024
DOI:https://doi.org/10.1016/j.matt.2024.10.007

Graphical abstract

Progress and potential

Organic photovoltaics (OPVs) currently suffer from high non-radiative voltage loss (ΔV_nr), which may limit them from far exceeding 20% efficiency. Disorder and energy offsets at donor/acceptor (D/A) interfaces play a crucial role in minimizing the ΔV_nr, but there are multiple types of D/A interfaces present in OPV active layers, which occludes current understanding of voltage losses. In this work, we combine optoelectronic measurements with local tunneling spectroscopy to identify the D/A interface relevant to ΔV_nr. We measure the electronic band edge distribution to infer interfacial charge transfer (CT) state properties of the D/A interface. This delineates the influences of CT state disorder and its hybridization with the singlet state on the ΔV_nr. Finally, our framework provides an ideal interface design rule toward minimizing voltage losses in next-generation OPV devices.

Highlights

•Tunneling spectroscopy and sensitive EQE combined to map CT state manifold
•Sharp interfaces with lowest-energy CT states exhibit minimal energetic disorder
•Minimizing S1-CT offset and CT disorder yield lowest non-radiative voltage losses
•Formulation and processing shown to reduce voltage loss by reducing CT disorder

Summary

Bulk heterojunction (BHJ) organic solar cells have made remarkable inroads toward 20% power conversion efficiency, yet non-radiative recombination losses (ΔV_nr) remain high. Here, we spatially map the energetic landscape of BHJs and ascribe charge transfer (CT) states to each interface, revealing where non-radiative recombination losses occur. We do so by locally mapping the energy distributions of modern PM6-based BHJs using scanning tunneling microscopy (STM) in combination with sensitive external quantum efficiency (s-EQE) analysis. The non-radiative energy losses are dictated by a combination of the singlet (S₁) to CT energy offset (ΔE_S1-CT) and the interfacial energetic disorder. PM6:Y6 achieves low ΔV_nr by forming a sharp donor/acceptor (D/A) interface with low interfacial disorder that can be tuned by judicious formulation and processing of the BHJ. The emerging design rule for low ΔV_nr in modern non-fullerene acceptors (NFAs) is to achieve sharp D/A interfaces with minimized ΔE_S1-CT and low interfacial electronic disorder of both D and A components.