Role of Solvents in the Preparation of Methylammonium Bismuth Iodide (MBI) Perovskite Films for Self-Biased Photodetector Applications

Abstract

Pb-free metal halide perovskites are excellent light-harvesting materials for photodetector applications because of their inherent remarkable optoelectronic properties with lower-temperature processability. However, to date, the realization of device-quality Pb-free metal halide films is still a great challenge. Here, using a single-step spin coating method, we have synthesized Pb-free methylammonium bismuth iodide [(CH3NH3)3Bi2I9 (MBI)] perovskite films using different solvents, such as γ-butyrolactone (GBL), 2-methoxyethanol (2ME), dimethyl sulfoxide (DMSO), and N,N-dimethyl formamide (DMF). Furthermore, MBI perovskite films were subjected to various characterization techniques to investigate and analyze morphological, optical, and structural properties. The formation of MBI thin films in various solvents was confirmed by XRD analysis and Raman spectroscopy. As evident from the XRD pattern, MBI belonged to the P63/mmc space group and had a hexagonal crystal structure. SEM analysis showed that the MBI film synthesized using different solvents has randomly oriented hexagonal-shaped grains parallel or orthogonal to the surface of the substrate. The synthesized perovskite films strongly absorbed light in the visible region with a higher absorption coefficient (∼105 cm–1) and an optical band gap of ∼1.85 to 2.0 eV, as evident from UV–vis and photoluminescence spectroscopy. TG analysis showed that MBI perovskites are thermally stable until ∼325 °C. It was found that MBI perovskite films prepared using a 2ME solvent have excellent substrate coverage with the smallest grain size and excellent optical properties. Finally, a photodetector was fabricated using an MBI perovskite film, exhibiting the fast rise and decay times of 0.79 and 0.36 s, with a responsivity of ∼8.0 × 10–2 mA/W and a detectivity of ∼5.0 × 108 Jones at a 0 V bias. The present results open up a new avenue for Pb-free, highly stable MBI perovskites for future self-biased photodetectors.

Bismuth-Based Perovskite Derivates with Thermal Voltage Exceeding 40 mV/K

“…In MABiI, the (00l) planes dominate the XRD spectrum, while (h0l) peaks are also significant in S.MABiI, indicating a less oriented polycrystalline structure than the undoped compound. Raman spectroscopy (Figure b) confirms that the [Bi 2 I 9 ] 3– octahedra are bonded to the CH 3 NH 3 + cations. ,, The peak at 116 cm –1 in the MABiI spectrum shifts to 120 cm –1 in S.MABiI, where a peak arises at 108 cm –1 . This has previously been reported in sulfur-doped MABiI samples, and it is related to the sulfur inclusion in the structure.…”

“…The crystal structure of S.MABiI and MABiI films, produced by drop-casting, showed hexagonal symmetry belonging to the P 6 3 / mmc space group, as confirmed by XRD ( Figure 1 a). 25 , 27 − 31 The main diffraction plain is (006) in both samples. In MABiI, the (00l) planes dominate the XRD spectrum, while (h0l) peaks are also significant in S.MABiI, indicating a less oriented polycrystalline structure than the undoped compound.…”

“…Raman spectroscopy (Figure 1b) confirms that the [Bi 2 I 9 ] 3− octahedra are bonded to the CH 3 NH 3 + cations. 7,26,31 The peak at 116 cm −1 in the MABiI spectrum shifts to 120 cm −1 in S.MABiI, where a peak arises at 108 cm −1 . This has previously been reported in sulfur-doped MABiI samples, 26 and it is related to the sulfur inclusion in the structure.…”

Bulk single crystal growth and optoelectronic properties of the quasi-two-dimensional perovskites (CH3NH3)3Bi2X9 (X− = Br− and I−)

“…At present, due to the superior optoelectronic properties, MA 3 Bi 2 I 9 has received extensive research attention in the field of semiconductor detectors and fruitful results have been produced. [65][66][67][68][69][70] Through the study of this work, the ultrafast decay time and superior environmental stability of MA 3 Bi 2 Br 9 also give the crystals important application prospects in the field of the ultrahigh time resolution detection of high-energy rays no matter whether through direct or indirect means. Meanwhile, the MA 3 Bi 2 (Br 0.74 I 0.26 ) 9 and MA 3 Bi 2 (Br 0.62 I 0.38 ) 9 mixed crystals exhibit excellent balance among the good absorption properties, suitable luminescence bands and good environmental stability, which are also valuable for obtaining photodetectors with balanced performances.…”

Synthesis of different organic ammonium-based bismuth iodide perovskites for photodetection application

“… 38 Moreover, Shah et al revealed that 2-methoxyethanol is the best solvent choice for the best coverage, smallest grain size, good optical properties, and better photo-response of the MA 3 Bi 2 I 9 perovskite thin film-based photodetector. 49 Mixed halides (Cl/I) of MA 3 Bi 2 I 6 Cl 3 -based photodetector have been reported to obtain photo-responsivities and specific detectivities roughly three times greater than pristine MA 3 Bi 2 I 9 -based devices. 50 In addition, one research work has also been reported with diammonium bismuth perovskites.…”