Double‐Side Crystallization Tuning to Achieve over 1 µm Thick and Well‐Aligned Block‐Like Narrow‐Bandgap Perovskites for High‐Efficiency Near‐Infrared Photodetectors

Abstract

Solution‐processed narrow‐bandgap Sn–Pb perovskites have shown their potential in near‐infrared (NIR) photodetection as a promising alternative to traditional silicon and inorganic compounds. To achieve efficient NIR photodetection, high‐quality Sn–Pb perovskite thick films with well‐packed, smooth, and pinhole/void‐free features are highly desirable for boosting the spectral absorption. Understanding the crystallization kinetics and tuning the crystallization are fundamentally important to reach such high‐quality thick Sn–Pb perovskite films, and have been limitedly explored. Herein, an approach of double‐side crystallization tuning through low‐temperature space‐restricted annealing in methylammonium‐free Sn–Pb perovskite films with over 1 µm thickness is proposed. More specifically, through simultaneously retarding the crystallization in the top of precursor films and promoting the crystal growth of the bottom of precursor films, high‐quality and block‐like thick FA0.85Cs0.15Sn0.5Pb0.5I3 perovskite films with improved crystallinity, preferred out‐of‐plane orientation, and reduced trap density are achieved. Finally, photovoltaic‐mode Sn–Pb perovskite NIR photodetectors show a high external quantum efficiency of ≈80% at 760–900 nm, a recorded responsivity of 0.53 A W−1, and a high specific detectivity of 6 × 1012 Jones at 940 nm. This study offers the fundamental understanding of the crystallization kinetics of thick perovskite films and paves the way for perovskite‐based emerging NIR photodetection and imaging applications.

Hybrid Halide Perovskite‐Based Near‐Infrared Photodetectors and Imaging Arrays

“…[ 24,69,71,119,120] Carrier lifetime ≈1-10 µs Time-resolved photoluminescence Time-resolved microwave conductance…”

“…Wallace C. H. Choy and co-workers have devoted extensive works in the crystallization kinetics of SnPb mixed perovskites and developing their efficient NIR photodiodes and imaging arrays. [24,25,218] They introduced Rb cations to MA Sn-rich SnPb mixed perovskites (the Sn content is 65%) to control crystallization for growing high-quality films. [25] Interestingly, incorporated Rb can effectively modify surface-energy-induced kinetic process.…”

“…Very recently, they first introduced thermally stable MA-free FA-Cs SnPb mixed perovskites to realize NIR photodetection. [24] To achieve sufficient NIR absorption and efficient devices, thick SnPb perovskite films (over 1 µm) are the key prerequisite, which had not been reported in PDs. They proposed an approach of double-side crystallization tuning through the low-temperature space-restricted annealing process to control the crystallization www.advopticalmat.de Adv.…”

“…Photodetectors (PDs) are the essential component of various modern photodetection and imaging techniques, including spectroscopy, optical fiber communication, silicon-based complementary metal-oxide semiconductor (CMOS) image sensing, Solution-processed and low-temperature hybrid halide perovskites possess the excellent photoelectric properties of high absorption coefficients (≈10 5 cm −1 ), tunable bandgaps (2.88-1.17 eV), excellent defect tolerance and low mid-gap defect densities, high carrier mobilities, long carrier lifetimes, and diffusion lengths. [17][18][19] These remarkable properties enable perovskites to become the limelight in optoelectronic devices, including X-ray imaging, [20][21][22] UV-vis-NIR PDs, [23][24][25][26] solar cells, [27] light emitting diodes, [28,29] and lasers. [30] Generally, perovskites have a common composition formula of ABX 3 (Figure 2a), where A shall be larger cations (e.g., methylammonium (CH 3 NH 3 + , MA + ), formamidinium (HN = CHNH 3 + , FA + ), cesium (Cs + ), rubidium (Rb + ), or their mixtures), B shall be smaller cations (e.g., lead (Pb 2+ ), tin (Sn 2+ ), or their mixtures), X shall be an anion (e.g., chlorine (Cl − ), bromine (Br − ), iodine (I − ), or their mixtures).…”

High-Performance Near-Infrared Photodetectors Based on the Synergy Effect of Short Wavelength Light Filter and Long Wavelength Response of a Perovskite/Polymer Hybrid Structure

“…Perovskite materials, owing to their high carrier mobility, effective charge collection, efficient light absorption, and low-cost preparation by the solution method, are widely used as active layer materials in solar cells − and photodetectors. ,− It was reported that the absorption range of perovskite materials can be effectively adjusted by changing the composition ratio of Cl – , Br – , and I – anions, which makes it possible to prepare a series of visible-blind spectrum tunable NIR photodetectors based on perovskite or perovskite/organic hybrid active layers. Lan et al reported the structure of CH 3 NH 3 PbI 3 (1700 nm)/PTB7-Th:PC 71 BM (200 nm) to accomplish an NIR narrowband perovskite-organic hybrid PDs with the CCN strategy.…”