Research Paper: Dopant-free hydrophobic fluorene-based HTMs with methoxy-triphenylamine and carbazole groups for improved perovskite solar cell performance

Summary

This study addresses the critical need for dopant-free, hydrophobic hole-transporting materials (HTMs) to enhance the stability and performance of perovskite solar cells (PVSCs), which are sensitive to moisture and oxygen. The main goal was to design and evaluate two new fluorene-core D–π–D-type organic HTMs, V1 and V2, featuring methoxy-substituted triphenylamine (V1) or N-phenyl-3,6-methoxy carbazole (V2) as peripheral donor groups. Key findings revealed that both V1 and V2 are strongly hydrophobic and possess suitable HOMO/LUMO energy levels for efficient charge extraction. V1 demonstrated superior optoelectronic properties, including better quenching of perovskite's luminescence, indicating improved interfacial contact and hole extraction compared to V2. PVSCs using dopant-free V1 achieved a power conversion efficiency (PCE) of 14.05% and retained 75% of their initial efficiency for over 480 hours in ambient conditions. Impedance spectroscopy confirmed higher charge recombination resistance for V1, indicating reduced recombination losses.

Why it matters

These findings are highly important for overcoming the stability and cost limitations of current PVSCs, which often rely on dopants that compromise hydrophobicity and long-term device integrity. The development of dopant-free, hydrophobic fluorene-based HTMs offers a simpler, more robust, and potentially lower-cost pathway to achieving long-lasting performance in PVSCs. This advancement is crucial for the commercialisation of next-generation solar energy devices by enhancing their durability against environmental degradation.

How Fluxim tools used

The Fluxim AG Paios system was extensively used for transient absorption studies, including transient photocurrent (TPC) and transient photovoltage (TPV) measurements. These capabilities allowed researchers to precisely investigate carrier extraction and recombination dynamics in the PVSCs. TPC/TPV studies confirmed that V1-based devices exhibited excellent hole extraction and lower non-radiative recombination compared to V2, directly correlating with its superior photovoltaic performance.

Publication Details

Bhat, V.G., Keremane, K.S., Subramanya, K.S., Archana, S., Hegde, A., Asuo, I.M., Poudel, B. and Dalimba, U.K. (2025), Dopant-free hydrophobic fluorene-based hole transport materials: impact of methoxy-substituted triphenylamine and carbazole peripheral groups on the performance of perovskite solar cells. Sustainable Energy Fuels, 9: 2769. https://doi.org/10.1039/d5se00120j