Electrochemically Assisted Growth of CsPbBr₃-Based Solar Cells Without Selective Contacts

Graphical Abstract

Minimizing the lead: A simple and cost-effective CsPbBr₃-based solar cell without ordinary selective contacts is reported. An electrochemical approach consisting of three successive steps: (1) electrodeposition of PbO₂ directly on top of FTO substrates, (2) heterogeneous phase reaction with gaseous HBr and (3) spin-coating of methanolic CsBr solutions followed by annealing was used. This method is more adequate for large-scale environmentally friendly production as it reduces chemical waste, particularly toxic lead.

Abstract

In this work we report a simple and cost-effective CsPbBr₃-based solar cell without ordinary selective contacts. To do so we follow an electrochemical approach consisting of three successive steps: (1) electrodeposition of PbO₂ directly on top of FTO substrates, (2) heterogeneous phase reaction with gaseous HBr and (3) spin-coating of methanolic CsBr solutions followed by annealing. This method is more adequate for large-scale environmentally friendly production as it reduces chemical waste, particularly toxic lead. The resulting films were structurally and optically characterized showing good coverage of the FTO substrates, absence of defects such as pinholes and orthorhombic structure. Photovoltaic and impedance characterization was carried out by pressing a carbon coated metal spring onto the CsPbBr₃ film until obtaining maximized open-circuit potential (V_oc) and short-circuit photocurrent density (j_sc) under simulated sunlight. The stabilized current at fixed voltage (SCFV) technique gave a maximum PCE value of 2.70 % close to devices with similar configuration. Impedance measurements demonstrated analogous behavior to that of state-of-art CsPbBr₃ based solar cells, comprising a recombination arc at mid-high frequencies, geometrical capacitance and ideality factors closed to 2, typical of SRH recombination in the perovskite bulk.