Air‐Stabilized Lead‐Free Hexagonal Cs₃Bi₂I₉ Nanocrystals for Ultrahigh‐Performance Optical Detection

Abstract

Broadband photodetectors possess enormous potentials for diverse applications while it is generally subjected to a lack of active materials with high performances under user-friendly conditions. Bismuth-based perovskites are promising and demonstrate better air stability than lead halide perovskites against moisture, heat, and light. In the present work, lead-free all-inorganic hexagonal Cs 3 Bi 2 I 9 perovskite nanocrystals are successfully fabricated via a modulated colloidal synthetic route. The Cs 3 Bi 2 I 9 nanocrystals are monodispersed with a size of ≈28 nm, which are applied for the construction of flexible Cs 3 Bi 2 I 9 detector and vertical heterogeneous structured photo detector of p-Si/Cs 3 Bi 2 I 9 /graphene. The flexible detector not only demonstrates excellent detective performance, but also yields high-resolution photographs as an imaging sensor. The p-Si/Cs 3 Bi 2 I 9 /graphene photodetector exhibits broad spectral response from ultraviolet to infrared light (254−1064 nm) with microsecond response time (31/34 µs). In particular, it performs with a high responsivity of 23.6 A W −1 and a high specific detectivity of 1.75 × 10 13 Jones under 650 nm illumination even in weak light intensity as low as 1 µW cm −2 , and exhibits excellent stability in ambient air, which is obviously ahead of the previously reported work. In addition, finite element analysis further demonstrates the excellent optoelectronic properties of Cs 3 Bi 2 I 9 materials and the broad spectral response of vertical heterojunctions.

Perovskite Solar Cell‐Gated Organic Electrochemical Transistors for Flexible Photodetectors with Ultrahigh Sensitivity and Fast Response

“…Therefore, our PSC-gated OECTs can achieve both high gain and fast response by coupling the fast response of perovskite photodiodes and the high transconductance of OECTs, realizing much higher R × bandwidth (BW) product (Figure 3f) and D* × BW product (Figure 3g) than those of state-of-the-art flexible photodetectors (Table S1, Supporting Information). [2,9,14,18,[52][53][54][55][56][57][58][59] Vertically stacked PSC-gated OECTs have been successfully prepared by attaching a flexible PSC on an OECT via a thin layer of free-standing ion gel (see Experimental Section for details). The device shows a high responsivity of 1.6 × 10 5 A W −1 , a high detectivity of 2.4 × 10 15 Jones and a fast response time of 0.89 ms under a low working voltage of −0.6 V (Figure S7, Supporting Information).…”

“…This limitation can be overcome by using our PSC-gated OECTs with fast response and high gain, which can resolve ambient light-skin interactions thereby realizing a convenient and low-power PPG sensor. As depicted in Figure 4a, the devices were attached on three different locations of the human body to monitor the PPG signals under [2,9,14,18,[52][53][54][55][56][57][58][59] g) Comparison of D* × BW products of PSC-gated OECTs with previously reported flexible PDs. [2,18,[52][53][54][55][56][57][58][59] ambient light, which showed similar PPG waveforms and HR (66 beats per minute).…”

Pressure‐Tuning Photothermal Synergy to Optimize the Photoelectronic Properties in Amorphous Halide Perovskite Cs3Bi2I9

“…Among the various perovskites, bismuth-based halide perovskites with high stability, low toxicity and the isoelectronic nature of Bi + compared to Pb + have attracted tremendous interest as photoelectric materials. [13][14][15][16] In particular, Cs 3 Bi 2 I 9 has already been extensively employed for the fabrication of high-performance photodetectors with excellent X-ray imaging capability, [14] impressive on/off ratio, [15] and broadband photoresponse (254-1064 nm). [16] Regrettably, except when used to assemble complicated heterojunctions, the intrinsic photoresponse of Cs 3 Bi 2 I 9 is limited to within the UV-vis waveband owing to its wide indirect bandgap of 1.9-2.8 eV.…”

“…[13][14][15][16] In particular, Cs 3 Bi 2 I 9 has already been extensively employed for the fabrication of high-performance photodetectors with excellent X-ray imaging capability, [14] impressive on/off ratio, [15] and broadband photoresponse (254-1064 nm). [16] Regrettably, except when used to assemble complicated heterojunctions, the intrinsic photoresponse of Cs 3 Bi 2 I 9 is limited to within the UV-vis waveband owing to its wide indirect bandgap of 1.9-2.8 eV. [8,16] Consequently, further exploring new strategies to extend the photoresponse range to enrich the functionalities and applications of Cs 3 Bi 2 I 9 is imperative.…”

“…[16] Regrettably, except when used to assemble complicated heterojunctions, the intrinsic photoresponse of Cs 3 Bi 2 I 9 is limited to within the UV-vis waveband owing to its wide indirect bandgap of 1.9-2.8 eV. [8,16] Consequently, further exploring new strategies to extend the photoresponse range to enrich the functionalities and applications of Cs 3 Bi 2 I 9 is imperative.…”