Pristine conductive metal–organic framework film as a cost-effective counter electrode for dye-sensitized solar cells

Abstract

The development of cost-effective and efficient alternatives to platinum (Pt) counter electrodes (CE) is critical for advancing dye-sensitized solar cells towards scalable and affordable applications. Here, we demonstrate the use of pristine, two-dimensional, conductive copper-benzenehexathiol metal–organic framework, CuBHT MOF, with a kagome lattice, as a Pt-free CE. Unlike conventional approaches that rely on MOF-derived metal-oxides or carbon composites, we utilize CuBHT in its unmodified form, leveraging its high electrical conductivity and π–d conjugation. Uniform CuBHT thin film was fabricated on fluorine-doped tin oxide substrates via the interfacial growth method. Structural and chemical analysis (powder X-ray diffraction analysis, Raman, and X-ray photoelectron spectroscopy) confirmed that the films retain the crystallinity and composition of bulk CuBHT powder, while scanning electron microscopy and atomic force microscopy demonstrated the formation of continuous films. Cyclic voltammetry revealed excellent electrocatalytic activity of CuBHT thin film towards both I₃⁻/I⁻ and I₂/I⁻ redox couples, comparable to Pt CE. Photovoltaic measurements and electrochemical impedance spectroscopy further demonstrated effective charge transfer and catalytic behavior, yielding a peak power conversion efficiency of 6.27 ± 0.02% surpassing that of Pt CEs (5.99 ± 0.01%) in reference devices. These findings establish CuBHT as a promising Pt-free CE for next-generation DSSCs.