Cu-Based Metal–Organic Frameworks for Photovoltaic Application

Abstract

In the present study, a thin layer of Cu-based metal–organic frameworks (MOFs, copper(II) benzene-1,3,5-tricarboxylate) is fabricated using a layer-by-layer technique, and the layer is investigated as a light-absorbing layer in TiO2-based solar cells. Iodine doping of the MOFs is performed to improve the conductivity and charge-transfer reaction across the TiO2/MOF/electrolyte interface. The HOMO and LUMO energy states of the MOF films are estimated to be −5.37 and −3.82 eV (vs vacuum), respectively, which show a well-matched energy cascade with TiO2. For the first time, a TiO2-based solar cell is fabricated successfully using iodine-doped Cu-MOFs as an active layer, demonstrating a cell performance with Jsc = 1.25 mA cm–2 and Eff = 0.26% under illumination of 1 sun radiation. In contrast, the cell with an undoped MOF layer exhibited Jsc = 0.05 mA cm–2 and Eff = 0.008%. Electrochemical impedance spectroscopy of the cells suggests that iodine doping significantly reduces the charge-transfer resistance.