TFB Boosts Y6 Device Efficiency in Organic Solar Cells

OPVs are a promising alternative to conventional silicon-based solar cells, offering advantages such as cost-effective manufacturing, lightweight construction, and flexible design. The introduction of NFA has significantly improved the performance of bulk heterojunction (BHJ) OPV devices, with recent advances increasing the PCE by almost 20%—a milestone in the commercialization of OPV technology. However, achieving high efficiency in OPVs requires precise control of the BHJ morphology, which complicates manufacturing.

Single-component OPV devices, such as those using Y6, offer a simpler approach. These devices rely on a single organic semiconductor to absorb light, which simplifies the design while maintaining efficient charge generation and transport. The ability of Y6 to generate free charges without traditional donor/acceptor interfaces makes it a strong candidate for efficient charge separation.

This study investigated the effects of different electron transport layers (ETLs) and HTLs on the performance of Y6 homogeneous OPV devices. The researchers specifically   analyzed the addition of poly[9,9- di-n  -octylfluorene -alt-N-(4-sec-butylphenyl)diphenylamine] (TFB) as a secondary HTL. TFB is known for its exciton blocking properties, which can significantly improve hole extraction in OPV structures.     

To evaluate the device performance, the researchers fabricated a reference OPV device with a standard structure: indium tin oxide (ITO)/PEDOT:PSS/TFB/Y6/BCP/Ag. They used various characterization techniques, including current density and voltage (JV) measurements and external quantum efficiency (EQE) experiments.

Variable-angle spectroscopic ellipsometry was also used to analyze the optical properties of the layers, providing insight into how different components interact in the device architecture.

The addition of a 30 nm TFB layer significantly improved the PCE of homogeneous Y6 OPV devices, from 0.21% to 2.57%. This improvement highlights the critical role of secondary HTLs in optimizing charge extraction and exciton blocking without introducing additional charge at the TFB/Y6 interface. Time-resolved photoluminescence (TRPL) spectroscopy confirmed that no exciton dissociation occurs at this interface, reinforcing the role of TFB in charge transfer rather than charge generation.

This study also evaluated devices using BCP and PNDI-F3N-Br as ETLs. While BCP facilitated charge generation at its interface with Y6, PNDI-F3N-Br had the least effect. These findings highlight the importance of selecting the appropriate combination of HTL and ETL materials to maximize device efficiency.

This research provides valuable insights into the future of organic solar cells. Improving efficiency in homogeneous devices with simplified architectures can support scalable manufacturing and enable integration into a variety of applications, including flexible electronics and building-integrated photovoltaics.

The findings of this study on charge generation pathways and surface interactions provide useful guidance for the development of new materials and device designs. The results suggest that the addition of TFB as a secondary HTL may be an effective strategy for improving other OPV systems and expanding the possibilities of materials and configurations for efficient solar energy conversion.

Furthermore, these findings may contribute to advances in other organic electronic devices, such as organic light-emitting diodes (OLEDs) and organic field-effect transistors (OFETs), by improving the understanding of charge transfer mechanisms.

As research advances, continued development of materials science and device engineering will be essential for the development of organic photovoltaics as a viable energy solution.

McAnally, S.,   et al  . (2025). High-efficiency Y6 organic solar cells activated by a secondary hole transport layer. Small Nano Micro . DOI: 10.1002/smll.202409485, https://onlinelibrary.wiley.com/doi/10.1002/smll.202409485     

Disclaimer: The views expressed here are those of the author, expressed privately, and do not necessarily reflect the views of AZoM.com Limited T/A AZoNetwork, the owner and operator of this website. This disclaimer forms part of the terms of use of this website.