Chirality Inducing Polar Photovoltage in a 2D Lead-Free Double Perovskite toward Self-Powered X-ray Detection

Abstract

Lead-free halide double perovskites (HDPs) have sparked broad interest in developing “green” photodetectors; however, self-powered X-ray detectors in this family remain elusive. Here, by exploiting the chirality-induced polar photovoltaic effect in a chiral-polar 2D HDP, (R-MPA)4AgBiI8 (1, R-MPA = R-β-methylphenethylammonium), we successfully realized self-powered X-ray detection. The significant spontaneous electric polarization in 1 gives it a large polar photovoltage of 0.36 V, which drives the separation and transport of X-ray-generated carriers, thus acquiring the capability of self-powered detection. Consequently, X-ray detectors based on high-quality single crystals of 1 exhibit a high sensitivity of 46.3 μC Gy–1 cm–2 and an ultralow detection limit of 85 nGy s–1 at zero bias. The sensitivity can be further increased to 949.6 μC Gy–1 cm–2 at 50 V bias, outperforming all current 2D HDP detectors. Our work is the first to demonstrate self-powered X-ray detection in single-phase lead-free HDPs, enlightening future design of “green” self-powered radiation detectors.

Room-Temperature Photoferroelectrics Semiconductor Driven by the Interlayer Confinement Effect

“…Subsequently, we test the stability of the dark current at 50 V bias, and the results show that even at high bias the drift value of the dark current was very small ( I drift = 4.96 × 10 –7 nA cm –1 s –1 V –1 ), which is sufficient to prove the stability of the device. The value of I drift at 50 V bias for the (IPA) 2 PbBr 4 single crystal device is smaller than the ( R -β-methylphenethylammonium) 4 AgBiI 8 single crystal detector ( I drift = 1.02 × 10 –3 nA cm –1 s –1 V –1 , 50 V bias), ( R -1-phenylpropylamine) 2 BiI 5 ( I drift = 1.0 × 10 –4 nA cm –1 s –1 V –1 , 10 V bias), and (2-iodopropylammonium) 2 FAPb 2 I 7 ( I drift = 7.76 × 10 –6 nA cm –1 s –1 V –1 , 10 V bias) . In addition to testing the stability of dark current, we also subjected the device to continuous X-ray irradiation to verify its radiation stability in Figure i.…”

Alternating chiral and achiral spacers for constructing two-dimensional chiral hybrid perovskites toward circular-polarization-sensitive photodetection

“…[1][2][3][4][5][6][7][8] In this star family, the chiral hybrid perovskites (CHPs) that integrate the chiroptical activities and semiconducting properties together, are particularly appealing and show promising applications in chiroptoelectronics, spintronics, and ferroelectrics. [9][10][11][12][13][14][15][16] After the first report of CHPs in 2003, 17 and the subsequent chiroptical study in 2017, 18 explosive research on CHPs has been conducted, resulting in a thriving group with diverse structural dimensionalities. Among them, the two-dimensional (2D) CHPs combine the advantages of flexible structures and excellent photoelectric properties, rendering them highly promising candidates for high-performance chiroptoelectronic devices, i.e., circularly polarized light (CPL) emitters and detectors.…”

“…23 In addition, 2D multilayered CHPs, i.e., (R/S-MPA) 2 (MA)Pb 2 I 7 (MPA = methylphenethylamine, MA = methylamine), were designed for seeking better electrical performance, 19 while 2D Pb-free chiral double perovskites of (R/S-MPA) 4 AgBiI 8 were created to deal with the Pb-toxicity problem. 14,24 We can see that CHPs are generally constructed by intentionally introducing chiral organic ligands. However, restricted by the limited number of size-suitable chiral organic amines, 25 the widespread construction of 2D CHPs with different compositions confronts tough challenges, which severely limits their structure and performance optimization as well as further applicability.…”

The Effect of Air Ionization in Testing Perovskite-Based Direct Conversion X-ray Detectors

“…Conventional photoconductive materials suffer from limitations such as low attenuation coefficient (a-Se) which results in low sensitivities and high production costs (CdTe). In recent years, various alternative materials, including HgI 2 , PbI 2 , and metal halide perovskites, − have been explored to address these challenges. Perovskites are intensively investigated due to their high attenuation coefficient, excellent charge carrier transport properties, and low production cost thanks to solution processability. − Going forward, the field is focusing on instability and reliability of perovskite materials and corresponding devices. − …”

“…Air is in fact used in X-ray detectors in ion chambers . We noticed that while some of the perovskite X-ray detectors , offer response currents on the order of microamperes, many others − report nanoamperes or even lower response currents, where the contribution of air ionization current may become non-negligible (Figure ). This raises concerns as air ionization can interfere with sensitivity estimation, necessitating the dissemination of appropriate evaluation methods for X-ray detectors.…”