Cu-Based Metal-Organic Frameworks for Photovoltaic Application

In the present study, a thin layer of Cu-based metal-organic frameworks (MOFs, copper(11) 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 J(sc)= 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 J(sc) = 0.05 mA cm(-2) and Eff = 0.00896. Electrochemical impedance spectroscopy of the cells suggests that iodine doping significantly reduces the charge-transfer resistance.This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2013009768), Republic of Korea. One of the authors (N.K.S.) is supported by The Korean Federation of Science and Technology Societies under Brain Pool program