Local Optoelectronic Characterization of Solvent-Annealed, Lead-Free, Bismuth-Based Perovskite Films

Abstract

Traditional organolead-halide perovskite-based devices have shown rapid improvements in their power conversion efficiency in less than a decade, yet challenges remain for improving stability and film uniformity, as well as the elimination of lead to address toxicity issues. We fabricated lead-free methylammonium bismuth iodide (MBI) perovskite films and studied the effect of solvent annealing with dimethylformamide (DMF) on both (1) the crystallinity and structure of the films with X-ray diffraction and scanning electron microscopy and (2) the local optoelectronic properties of the films as measured via (photo)conductive atomic force microscopy. We found that solvent annealing leads to improved crystallinity and increased grain size in the MBI films as compared to the thermally annealed films. Furthermore, solvent-annealed MBI films show significantly increased electrical conductivity in the out-of-plane direction. Photoconductivity in both solvent-annealed and thermally annealed MBI films was increased in the grain interiors versus the grain boundaries. It was observed that DMF-induced solvent annealing impacts charge transport through the film, which can be a unique design parameter for optimizing local optoelectronic properties. By studying how solvent annealing affects the MBI film structure and changes the ways in which charges are transported through the film, we have developed a better understanding of how local optoelectronic properties are affected by DMF annealing.

Potential Substitutes for Replacement of Lead in Perovskite Solar Cells: A Review

“…The solvent annealing in (MA) 3 Bi 2 I 9 films enhances its electrical conductivity. The DMF‐induced solvent annealing impacts the charge transport through the films . The morphology of (MA) 3 Bi 2 I 9 perovskite film can also be enhanced by incorporating a small amount of N‐methyl‐2 pyrrolidone (NMP) into the MBI‐DMF solution.…”

“…The DMF-induced solvent annealing impacts the charge transport through the films. [243] The morphology of (MA) 3 Bi 2 I 9 perovskite film can also be enhanced by incorporating a small amount of N-methyl-2 pyrrolidone (NMP) into the MBI-DMF solution. The addition of various concentration of NMP into the precursor solution not only controls the rate of crystallization but also enhanced SPCE to a value of 0.31% and stability for 30 d in a relative humidity of 50-60%.…”

A Facile Air‐Retreatment Strategy for Efficient Inverted Perovskite Solar Cells

“…Solvent annealing have been widely reported to increase the grain size of perovskite and enhance the performance of PSCs accordingly . N , N ‐Dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are usually used in solvent annealing .…”

Reversible Thermochromism in All‐Inorganic Lead‐Free Cs3Sb2I9 Perovskite Single Crystals

“…[1][2][3] Nevertheless, challenges relating to stability and toxicity of Pb-based perovskites have prompted researchers to explore Pb-free perovskite semiconductors. [4][5][6][7][8] To extend the photophysical performance of Pb-free perovskites, effect of external regulatory factors such as pressure, [9] temperature, [10,11] chemical doping, [8] alloying, [12] etc., are being explored. Expansion or contraction of interatomic distances caused by external factors like temperature and pressure has the potential to change the bandgap of hybrid perovskites.…”