Solution Processed Bismuth Ferrite Thin Films for All-Oxide Solar Photovoltaics

The present work delivers the first assessment of BiFeO3 (BFO) thin films as an absorber for sustainable all-oxide photovoltaic devices. Films are deposited from a metalorganic precursor complex solution followed by annealing in air at 673 K for 2 h. X-ray diffraction, complemented by quantitative analysis, indicated formation of pure BFO with rhombohedral structure (R3C). Atomic force microscopy suggests deposition of compact and smooth films with spherical particles of sizes similar to 150 nm. A direct band gap of 2.2 eV is ascertained from UV-vis-NIR spectroscopy. Mechanistic aspects of the BFO formation are discussed based on thermograveminetric analysis, differential scanning calorimetry, and infrared spectroscopy of the precursor complex. A proof-of-concept BFO/ZnO heterojunction based solar cell fabricated by solution processing delivered a photoconversion efficiency of 3.98% with open-circuit voltage (Voc), short-circuit current density, and fill factor of 642 mV, 12.47 mA/cm(2), and 50.4%, respectively. The device exhibits a maximum external quantum efficiency of nearly 70%. These parameters are among the highest values reported for all oxide PV. Analysis of the V-oc, series resistance, and conversion efficiency as a function of temperature revealed valuable information about recombination processes.