Research Paper: Coordination-Based Doping of MEH-PPV with La(TFSI)3 Enables Air-Free Conductivity 2 and Stable Performance in Perovskite Solar Cells

Summary

This study investigates a novel coordination-based doping strategy using lanthanum bistriflimide [La(TFSI)3] for MEH-PPV conjugated polymers, aiming to achieve high electrical conductivity and stability under air-free conditions. This addresses a central challenge in organic optoelectronic device development. Key findings demonstrate that La(TFSI)3 doping dramatically increases MEH-PPV conductivity by over six orders of magnitude in inert environments, a stark contrast to monovalent dopants like LiTFSI, which often require environmental activation. This enhancement is attributed to La3+ forming multidentate coordination complexes that induce crosslinking and suppress emissive disorder, leading to improved interchain charge hopping and structurally cohesive films free of pinholes. When applied as a hole transport layer (HTL) in perovskite solar cells (PSCs), La(TFSI)3 doped MEH-PPV boosted the power conversion efficiency (PCE) from 13.05% to a significant 18.50%. Crucially, these PSCs maintained 100% of their initial efficiency after 1000 hours of inert storage, far exceeding LiTFSI-doped devices which degraded after 600 hours.

Why it matters

These findings are crucial for developing durable, high-performance organic electronics by providing a scalable, air-free doping strategy that enhances both conductivity and morphological stability in conjugated polymers. Overcoming the reliance on oxygen activation and preventing detrimental morphological defects, this research offers a promising pathway for more robust and long-lived perovskite solar cells and other optoelectronic devices, accelerating their commercial viability.

How Fluxim tools used

The FLUXiM Paios system was utilized for comprehensive electrical characterization of perovskite solar cells. Specifically, Paios provided 1 sun AM1.5G illumination for J-V characterization and was used for transient photocurrent measurements. These transient measurements were crucial for determining the carrier lifetime, revealing that La(TFSI)3 doping significantly shortened this lifetime (from 0.84 µs to 0.59 µs for pristine vs La(TFSI)3 doped HTL), thereby confirming more efficient and rapid charge extraction in the doped devices.

Publication Details

McPherson, Seth W. and Chou, Yeh-Chuan and Shin, Insoo and Maclean, Stephen A. and Li, Tai-De and Lin, Chieh-Ting and Kong, Jaemin and Rohr, Jason A. and Taylor, André D., Coordination-Based Doping of Meh-Ppv with La(Tfsi)3 Enables Air-Free Conductivity and Stable Performance in Perovskite Solar Cells. Available at SSRN: https://ssrn.com/abstract=5343209 or http://dx.doi.org/10.2139/ssrn.5343209