All‐Inorganic Halide Perovskite Nanocrystals: Future Prospects and Challenges to Go Lead Free

Abstract

Organometallic halide perovskite (OHP) received tremendous attention from the science community for their unprecedented optoelectronic properties, such as large absorption coefficient, long electronÀhole diffusion length, high carrier mobility, and excellent tunability of optical bandgap. [1][2][3][4][5][6] Within 10 years, the efficiency of OHP-based solar cells increases from <10% to 25.5%. [7][8][9][10][11][12] Such unimaginable development speed overcomes all kinds of traditional semiconductors overwhelmingly. Typical OHP materials have the composition ABX 3 , where A is organic cation, methylammonium,B is a tetravalent metal cation (Pb; Sn; Ge); and X is a halide anion (Cl, Br, I). [13][14][15][16] Moreover, the fascinating tunability of absorption and emission wavelength along with high carrier mobility make it a potential candidate for light-emitting diodes (LEDs) and photodetector (PD) applications also. [17][18][19][20][21] Large-area, flexible, and several architectures of solar cells have been fabricated to meet the requirement of device integration and future applications. Despite all the aforementioned advantages, OHP nanocrystal (NC)-based devices face a major challenge in terms of stability. [22][23][24][25][26][27] The OHP NCs are extremely sensitive to oxygen and moisture; therefore, the synthesis and storage require a highly controlled environment. Apart from environment issues, photo-and thermal stability problems are also observed in OHP NCs. [28][29][30] Since past 3À4 years, efforts have been made to overcome stability issues. Stability has been improved by replacing methylammonium (MA) by formamidinium (FA), by integrating OHP with polymers, and using inorganic carrier transport layers instead of organic ones. [23,[30][31][32][33] People have tried to mix CsPbX 3 with OHP to get better device performance. Lee et al. [34] substituted FA þ ion by Cs þ partially and recorded higher stability against photons and humid environment. Saliba et al. [35] have synthesized MA þ , FA þ , and Cs þ mixed-perovskite NCs and observed good stability against ambient atmosphere. Despite all the efforts to stabilize the device, the stability for practical application is yet to be achieved. It is well known that the photo-and thermal stabilities of inorganic materials are much higher than that of the organic materials. Keeping all the issues in mind, Protesescu et al. [36] have synthesized all-inorganic halide perovskite (IHP) CsPbX 3 colloidal NCs. All IHP NCs show very good thermal and photostability, which make them promising replacements of OHP for future device applications. [37][38][39] 2. Inorganic Halide Perovskite (IHP) IHP materials are very closely related to the family of OHP materials, which can be exploited to overcome all the shortcomings of the latter. Investigations have shown that the inorganic monovalent cation Cs þ can satisfy the requirements of the ABX 3 structure, replacing MA þ and FA þ as the A-site ions to form highly thermal stable CsBX 3 perovskites (>350 C). At the same time, CsBX 3...

Advanced Halide Scintillators: From the Bulk to Nano

“…[334] Recent reviews explore their stability in detail, including proposed strategies to solve this by adjusting reaction conditions, changing composition, or surface passivation. [42,289] However, for application in scintillation detectors, immobilization of the NCs in a solid monolith matrix is needed. Some recent reviews discuss progress on such matrices as well [335,336] but with different target applications in mind.…”

“…[ 37–39 ] Recently, a body of studies on lead halide perovskites has also been focused on their application in scintillation detectors; see recent review papers. [ 40–43 ]…”

“…[37][38][39] Recently, a body of studies on lead halide perovskites has also been focused on their application in scintillation detectors; see recent review papers. [40][41][42][43] The aim of this review is to provide a broad overview in the field of halide scintillators studied in the past decade focusing on material composition and its scintillation performance and also on new trends in nonsingle-crystal systems' R&D trying to explain the added value which they might bring if their manufacturing technology will advance enough.…”