Effect of Solvent Vapour Annealing on Bismuth Triiodide Film for Photovoltaic Applications and its Optoelectronic Properties

We report on solution-processed bismuth triiodide (BiI3) solar cells and their optoelectronic properties under different fabrication approaches. The BiI3 films crystallized by annealing under controlled solvent vapour conditions were found to have dominant effects on film morphology as well as the crystal growth. The photovoltaic device with BiI3 film followed by annealing under a chlorobenzene vapour atmosphere demonstrated the best power conversion efficiency of ∼1.01% with an open circuit voltage of 0.587 V in the inverted device configuration. This is attributed to the improvement in film quality comprising uniform morphology, increase in grain size, and hence mitigation of defect profile. Based on the material growth properties, and device analysis, our report provides insight into the correlation between film morphology, opto-physical properties, and defect profile in the BiI3 based device.