Double Free: A Promising Route toward Moisture-Stable Hypotoxic Hybrid Perovskites

Abstract

The moisture instability and toxicity of lead have hindered the development of lead organometal halide perovskites (Pb-OHPs). Similar to Pb-OHPs, OHPs based on Pb-free elements, including VA-group metals Bi and Sb (denoted as M), exhibit optoelectronic properties due to their isoelectronic configuration and close chemistry of the lone-pair ns 2 state. However, M-OHPs are mostly based on hydrophilic protonated organic countercations and possess low structural dimensionalities, which affect the moisture stability and disrupt continuous carrier transport, respectively. Herein, we demonstrate a "double-free" strategy to realize the rational synthesis of moisture-stable hypotoxic hybrid perovskites. A hydrogen-bond-free alkylated countercation was assembled with Pb-free OHP bearing an extended structure in one molecule. As a proof of concept, two double-free M-OHPs are synthesized, which show greatly improved moisture and photostability than their corresponding hydrogen bond OHPs and the extensively studied MA 3 M 2 X 9 (MA = CH 3 NH 3 + ).The photoconduction behaviors of both double-free OHPs display short rise and decay recovery time and exhibit excellent photocurrent reproducibility. Importantly, (1-methyl-4-phenylpyridin-1-ium)BiI 4 (Me4ppi-BiI 4 ) displays a comparable switching on/off ratio with MA 3 Bi 2 I 9 , and can endure 75% relative humidity for at least 243 days. The photophysical property measurements and theoretical calculation show that the remarkable photoconversion performance results from the relatively low exciton binding energy and greatly improved carrier mobility and concentration.

A halogen bonding assembled hybrid copper halide framework as a promising hypotoxicity photodetector

“…The tendency is similar to its optical absorption plot and also suggests its broadband detection ability. 53 This result indicates that BCS-CuI could act as a promising lead-free candidate for potential photodetection application in the visible light range.…”

“…The typical linear and symmetrical features of the plots suggest a typical Ohmic contact between the polycrystalline film and the Au electrode. The device has a low dark current of 0.18 nA in the circuit, which dramatically increased to 5.92 nA (light current) on applying a positive bias voltage of 5 V. The intense photoresponse gives an on/off ratio of 32.9, which is obviously larger than that of MA 3 Bi 2 I 9 (3.87) 53 and K 2 Cu 2 Cl 6 (∼2) 54 with lower structural dimensionality (Fig. S10, † for more comparisons see Table S6 †).…”

Ultrathin covalent and cuprophilic interaction-assembled copper–sulfur monolayer in organic metal chalcogenide for oriented photoconductivity

“…The intense light response afforded an on/off ratio of 8.21, which was obviously larger than the well-known lead-free photoconductor MA 3 Bi 2 I 9 (3.87 under the same experimental conditions, MA = CH 3 NH 3 + , Fig. S11, ESI†) 27 and the previously reported Cu-based photoconductors K 2 Cu 2 Cl 6 (∼2) 28 and (Mebti) 2 Cu 3 I 5 (1.94). 24 The transient photocurrent response of the photoconductive device shows good repeatability of photocurrent under photo-switching conditions (Fig.…”

Water-Stable Hybrid Lead-Free Perovskite for Negative Temperature Coefficient Thermistors

“…This stability performance is significantly superior to MA 3 Bi 2 I 9 , which remains stable only 2 days under similar conditions (Figure S10). 30 To disclose the differences in moisture stability, a more severe and time-saving evaluation was conducted on (Me 3 TMP)Bi 2 I 9 and (H 3 TMP)BiI 6 . The powdery samples of the two compounds were directly soaked in deionized water for different days.…”