Perseverance of direct bandgap in multilayer 2D PbI ₂ under an experimental strain up to 7.69%

Abstract

The two-dimensional (2D) materials are naturally suitable for various flexible 2D optoelectronic devices, in which the direct band gap perseverance is crucial because the flexibility deformations often cause a bandgap transition and thus break performance of the devices. Most of 2D transition metal dichalcogenides (TMDs) materials such as monolayer MoS 2 , WS 2 and MoSe 2 have been thought to be not suitable for flexible optoelectronic devices due to their direct-to-indirect bandgap transition even under a small strain (~1%-2%) for any flexibility deformations. So far, only 2D phosphorene has been theoretically predicted to be able to keep direct bandgap property under a large strain. Here we report a 2D material lead iodide (PbI 2 ) mutilayer with a direct band gap and find by photoluminescence (PL) measurements that it maintains a direct bandgap nature under a large experimental strain up to 7.69%. Theoretical simulations support and explain well our experimental results.

PbI2 Single Crystal Growth and Its Optical Property Study

“…The high energy emission peak at 2.43 eV refers to the free excitonic recombination. On the basis of PL and absorption measurements, we demonstrate that our PbI2 crystal is a direct semiconductor [21]. For the purpose of studying the temperature dependence of band gap energies, we performed the temperature-dependent transmittance measurements in the temperature range between 20 and 300 K. Figure 4a shows the absorption spectra measured at different temperatures, and the inset figure shows the comparison of reflectance and absorption spectra.…”

“…The high energy emission peak at 2.43 eV refers to the free excitonic recombination. On the basis of PL and absorption measurements, we demonstrate that our PbI 2 crystal is a direct semiconductor [21]. In order to identify the band gap energy, we performed the transmittance and photoluminescence (PL) measurements at 300 K. At sub-band gap photon energies, a semiconductor is basically transparent, meaning that no photon absorption happens in this energy range and most of the incident light can pass through the sample.…”

Recent Advances in Strain-Induced Piezoelectric and Piezoresistive Effect-Engineered 2D Semiconductors for Adaptive Electronics and Optoelectronics

“…Besides, these experimental results are good agreement to theoretical models. Recently, Du et al [155] used the same method and found that the 2D PbI 2 multilayer maintains a direct band gap nature under a large experimental strain up to 7.69%. The strained 2D PbI 2 offers reference for potential optoelectronic device applications.…”

Enhanced Photostability and Photoluminescence of PbI2 via Constructing Type‐I Heterostructure with ZnO

“…[17,18] Therefore, PbI 2 could become a good supplement for the existing TMDs and other 2D optoelectronic materials. In addition, PbI 2 has a wider bandgap, higher light absorption coefficient, and better perseverance of direct bandgap than TMDs materials, [19][20][21][22][23] and has potential applications in nuclear radiation detectors, [24] low-threshold lasers, [25] and high-efficiency photodetectors. [26] However, there is a fly in the ointment, that is, the stability, especially photostability, of PbI 2 is inferior to that of TMDs materials.…”