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Abstract
Integrated on-chip femtosecond (fs) laser optoelectronic system, with photodetector as a critical component for light-electrical signal conversion, is a long-sought-after goal for a wide range of frontier applications. However, the high laser peak intensity and complicated nanophotonic waveguide structure of on-chip fs laser are beyond the detectability and integrability of conventional photodetectors. Therefore, flexible photodetector with the response on intense fs laser is in urgent needs. Herein, we demonstrate the first (to our knowledge) two-photon absorption (TPA) flexible photodetector based on the strong TPA nonlinearity of layered hybrid perovskite (IA)2(MA)2Pb3Br10, exhibiting efficient sub-bandgap response on the infrared fs laser at 700-1000 nm. High saturation intensity up to ∼3.8 MW/cm2 is achieved. The device also shows superior current stability even after bending for 1000 cycles. This work may pave the new way for the application of flexible optoelectronics specialized in integrated fs-laser detection.
© 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Benefiting from the coexistence of ultrastrong/ultrafast spatiotemporal features with wide-band tunability, power saving, low cost, as well as greatly reduced footprint and weight, on-chip integrated fs-pulse sources have become critical components for a wide array of applications, such as optical atomic clocks, coherent optical communications, quantum information processing, ultrafast light ranging, and optical frequency synthesis [1–4]. At the same time, the urgent need for high-performance integrated fs-laser detection devices is put forward. The optoelectrical effect of multiphoton absorption, such as two-photon absorption (TPA), has been considered as one of the most efficient ways for fs-laser detection with ultrahigh saturation intensity [5–8]. TPA refers to a third-order nonlinearity process, where two below-bandgap-energy photons are absorbed simultaneously by a semiconductor under intense light excitation, accompanied with the transition of electron from valence band to conduction band. With utilizing the TPA process, sub-bandgap photodetectors which can convert fs laser into electrical signals have been widely explored [5–11]. A series of promising TPA photodetectors have been demonstrated to offer great potentials in fs-laser signal measurement [12–15]. However, the TPA photodetectors in literature are mainly fabricated with bulk semiconductors and micro-/nano-materials on rigid substrates [5–10], challenging to integrate them into on-chip fs-laser systems which usually contain complex waveguide structure and curved interface.
Flexible photodetector, capable of bendability, foldability, and stretchability, has proven to be a promising component with flexible interconnects for constructing highly-integrated and miniaturized optoelectronic systems [16–20]. Recently, layered organic-inorganic hybrid perovskites (OIHPs) attract major research interests owing to their unique flexible crystal structure constructed from alternately stacked molecular sheets of organic cations and inorganic perovskite skeletons [21–23]. The successful cleavage of two-dimensional (2D) thin sheets from OIHP bulks has led to their extensive investigation in flexible photodetectors [24–27]. Layered OIHPs are also recognized as excellent nonlinear materials with strong multiphoton absorption effect [9,28–31]. There have been a few prominent works on the TPA photodetector with layered OIHPs on rigid substrates [9], which encourages the further technological advancements at flexible platform.
In this work, we demonstrate a flexible photodetector with the layered OIHP (IA)2(MA)2Pb3Br10 (IMPB, IA = isoamylammonium and MA = methylammonium). Based on the TPA effect of IMPB, the as-prepared photodetector is able to detect the fs laser in the near-infrared (NIR) wavelength region of 700-1000 nm, in which the maximum responsivity related to the fs-pulse peak power is 21 and 5.5 nA/W at 700 and 1000 nm, respectively, corresponding to the detectivity of 552.3 and 136.4 Jones. The saturation intensity is larger than 3.8 MW/cm2. Additionally, this photodetector exhibits excellent flexibility and stability that only small attenuation of photocurrent can be observed even after bending 1000 times. These advantages reveal the great potential of TPA flexible photodetectors in fs-laser detection applications that not only can serve as light-electrical signal conversion in on-chip fs-laser integration, but also may implement wearable alarm for monitoring fs-laser leakage.
2. Materials and methods
2.1 Synthesis of the bulk crystals
First, the lead acetate trihydrate (20 mmol, 7.59 g) was measured and put in a beaker of 500 ml volume. Then, 20 ml hydrobromic acid solution was taken with a measuring cylinder and slowly drained through a glass rod. Next, methylamine (10 mmol, 0.77 g) and isoamylamine aqueous solutions (20 mmol, 2.02 g) were weighed successively and slowly added to the mixed solution. Under the heating condition of 100 °C, the clarified solution was obtained after continuous stirring for ∼30 min, and the small particle seed crystals of the target compound were precipitated after cooling to room temperature. Before crystal growth, a saturated hydrobromic solution of the compound is prepared at 60 °C and then kept at 65 °C for ∼3 h. Subsequently, high quality seed crystals were immersed in the solution and large crystals were grown through the top seed growth method. Finally, the yellow flake crystals were obtained in the saturated solution through temperature cooling process, where the temperature cooling rate was 0.5 °C/d.
2.2 Crystal characterization
The single crystal X-ray diffraction was performed on the Bruker D8 diffractometer with Mo Kα radiation (λ = 0.77 Å). Crystal structures were solved by direct methods and confirmed by the full-matrix least-squares refinements on F2 using the SHELXTL software packing. All non-hydrogen atoms were refined anisotropically, and hydrogen atoms were generated by geometrical method and refined using the Olex2 software. The linear absorption spectrum was measured at room temperature on the Perkin-Elmer Lambda 900 UV-Visible-NIR spectrometer. The thickness of the exfoliated microcrystal on the electrodes was measured on the Dimension ICON atomic force microscopy.
2.3 TPA-induced upconversion PL measurement
For the TPA-related optical measurements, a Ti:sapphire mode-locked oscillator (Chameleon, Coherent; ∼120 fs, 80 MHz, 680-1020 nm) was used as the excitation source. A continuously variable neutral density filter was utilized to adjust the intensity of excitation laser. For the upconversion PL measurement, a circular lens with the focal length of 80 mm was employed to focus the laser vertically onto the crystal flake with the thickness of ∼0.5 mm. The PL signals were collected by an optical fiber and coupled to the spectrometer (QE Pro, Ocean Optics) in the reflection spectroscopy geometry. The fiber port was fixed as close as to the sample with a small angle of ∼10°.
2.4 Open-aperture Z-scan measurement
The incident laser beam was divided into two parts by a 10:90 beam splitter. One part was directed into a power detector (DR) as the reference, while the other part was focused onto the crystal flake with the thickness of ∼60 µm by a circular lens with the focal length of 200 mm, and the beam transmitted through the sample was detected by another power detector (DS) as the signal. The incident beam was propagating along the crystallographic a-axis and the sample moved along the propagating direction of the beam, i.e., z-axis. The transmittance was recorded as a function of the sample position (z). As the incident power can be regarded as a constant, the sample will be subjected to various peak intensity I(z) at different z and subsequently the change of transmittance. The diameters of the laser beams at different z were measured through knife-edge scans along the x-axis direction of the cross-sectional plane.
2.5 Determination of the TPA absorption coefficients
As a nonlinear optical effect, the MPA process can be described by the following expression
2.6 Fabrication of the photodetector
The interdigital electrodes (5 nm Cr/ 50 nm Au) were prepared on the polyethylene terephthalate (PET) substrate by the conventional UV lithography and electron-beam evaporation procedure. The length and width of the finger are 100 and 10 µm, respectively, and the finger spacing is 9 µm. The microcrystal of IMPB was mechanically exfoliated with the scotch tape from its bulk crystal, and then transferred directionally onto the electrodes with the heat-release tape. Finally, the device was annealed at 70 °C in vacuum atmosphere for 2 h.
2.7 Photodetection measurement
The I-V and I-t measurements on the IMPB photodetector were performed using a Keithley 2450 source-meter. The laser was focused by a 10× objective lens and incident vertically from the back of the device onto the channel area. A thermoelectric detector (S350C, Thorlabs) was used to measure and calibrate the intensity of the incident laser.
3. Results and discussions
Balance between the TPA nonlinearity and electrical transport in OIHPs is the key to realize excellent TPA photoresponse. The primary aspect is to utilize a mass of excitons to greatly enhance the TPA nonlinearity of OIHPs, because excitons can be regarded as the transition dipole moments, and the collection of them can remarkably improve the macroscopic nonlinear optical susceptibility [32–36]. The second aspect is to ensure a certain number of excitons are capable of dissociation under the electric field of bias voltage to increase the channel conductivity. Following these above points, we predicted that the IMPB structure should be great potential in TPA photodetection as schematically shown in Fig. 1(a), in which the bilayered organic cations IA+ are anchored to the inorganic skeletons composed of trilayered corner-sharing PbBr64- octahedra via strong hydrogen bond interaction, with the protonated organic cations MA+ residing in the voids surrounded by PbBr64- octahedra, while the two adjacent IA+ cations are linked together by weak van der Waals force. This character makes the bulk crystals easily be cleaved into microcrystals through mechanical exfoliation method. Our former study has revealed that the alternative arrangements of the organic and inorganic layers constitute the Type-I periodic quantum well structure of IMPB, in which inorganic layers make crucial contribution to its bandgap. In addition, the thickness of the well is ∼1.8 nm, suggesting that the electrons and holes are strongly confined within the wells, leading to the increased probability of radiative recombination [28], so that enhanced TPA properties can be obtained in this material structure. The IMPB single crystals were synthesized through the temperature-cooling method in aqueous solution as demonstrated in our previous work [28], and the corresponding photograph of the as-grown crystal at millimeter scale is presented in the inset of Fig. 1(a). The linear absorption spectrum exhibits an absorption cutoff around 520 nm (Fig. 1(b)), and the optical bandgap energy is estimated to be 2.4 eV according to the Tauc equation (the inset of Fig. 1(b)). The X-ray diffraction (XRD) patterns display a series of diffraction peaks corresponding to the (200) family of crystal planes (Fig. 1(c)), indicating the highly oriented arrangement of crystal growth parallel to the crystallographic a-axis direction, which is beneficial to realize superior charge transport in IMPB-based photodetection devices.
Fig. 1. Structural and physical properties of IMPB. (a) Diagram of the crystal structure for top view in ac plane. Inset: photograph of the single crystal. (b) Linear optical absorption spectrum and the corresponding Tauc plot. (c) XRD patterns of the crystal wafer.
The TPA properties of IMPB single crystal under the excitation of NIR fs laser were investigated by characterizing the TPA-induced photoluminescence (PL). This PL emission process can be schematically illustrated in Fig. 2(a). One valence electron is excited to the conduction band by absorbing the energies of two NIR photons simultaneously via a virtual energy level, then relaxes to the bottom of conduction band through electron-phonon interaction, followed by radiative recombination with upconversion photon emission around 520 nm. To measure the PL characteristics of IMPB, we used a Ti:sapphire mode-locked resonator (680-1020 nm, 80 MHz, ∼120 fs) as the excitation laser source. The bulk crystal was placed on the focal plane with the laser beam propagating along its a-axis direction. Upon fs-laser excitation, TPA-induced PL emission was observed in the wavelength range of 700-1000 nm as the corresponding photograph shown in the inset of Fig. 2(a). The recorded upconversion PL spectra at the different excitation intensities (${I_{\textrm{ex}}}$) are presented in Fig. 2(b) (λex = 1000 nm) and Fig. S1 in Supplement 1 (λex = 700, 750, 800, 850, 900, and 950 nm). It can be seen that all the PL spectra are centered around 520 nm. The dependence of PL intensity (${I_{\textrm{PL}}}$) on ${I_{\textrm{ex}}}$ are extracted from these intensity-dependent PL spectra. As shown in the insets of Fig. 2(b) (λex = 1000 nm) and Fig. S1 in Supplement 1 (λex = 700-950 nm), the slopes (η) of the fitting curves for the experimental data in logarithmic plot are all around 2 (i.e., ${I_{\textrm{PL}}} \propto I_{\textrm{ex}}^2$, which is summarized in Fig. 2(c)), in agreement with the perturbative nonlinear-optics theory [37], and thus verifying the TPA nature of the PL processes at λex = 700-1000 nm.
Fig. 2. TPA properties of IMPB. (a) Schematic illustration of the TPA-induced PL emission process. Inset: photograph of the upconversion PL emission from the bulk crystal. (b) Upconversion PL spectra under the different ${I_{\textrm{ex}}}$ (λex = 1000 nm). Inset: logarithmic plot of the PL intensity dependence on ${I_{\textrm{ex}}}$. The solid green dots are the experimental data, and the solid red line is the linear fitting curve. (c) Histogram for the slopes of the linear fitting curves at the different excitation wavelengths. (d) Schematic diagram of the experimental setup for Z-scan measurement. (e) Normalized transmittance as a function of ${I_{\textrm{ex}}}$ for TPA process (λex = 1000 nm). The solid red line is the TPA fitting curve. Inset: the measured Z-scan curve. (f) Histogram for the TPA absorption coefficients measured at the different excitation wavelengths.
To quantitatively assess the TPA performance of IMPB, the open aperture (OA) Z-scan measurement was performed with the experimental setup schematically shown in Fig. 2(d). The measured Z-scan curves and the derived normalized transmittance as a function of ${I_{\textrm{ex}}}$ are presented in Fig. 2(e) (λex = 1000 nm) and Fig. S2 in Supplement 1 (λex = 700-950 nm). Furthermore, based on these results, the TPA absorption coefficient (β) at different excitation wavelength is obtained as listed in Fig. 2(f) according to the TPA nonlinear-optics theory (see Section 2.5 in Materials and methods for details). These β values are one to six orders of magnitude larger than those of some typical materials ranging from traditional inorganic semiconductors and organic dyes to currently widely studied transition metal dichalcogenides and two/three dimensional perovskites [9,38–53], suggesting the superior TPA performance of IMPB (the detailed comparison with other materials is provided in Table 1).
Table 1. Comparison of the TPA absorption coefficient (β) between IMPB and other typical TPA materialsa
To address whether the TPA properties can be maintained in the mechanically exfoliated microcrytals, we carried out the TPA-induced PL characterization for the microcrystal of IMPB (the thickness is ∼200 nm, on the quartz substrate). As shown in Fig. S3 in Supplement 1, under the excitation of fs laser (λex = 1000 nm), the TPA-induced PL spectra of the microcrystal at varied excitation intensities are all centered around 520 nm as the case of bulk sample (Fig. 2(b)). Furthermore, the PL intensity shows quadratic dependence on the excitation intensity (the inset of Fig. S3 in Supplement 1), verifying that the TPA properties are not destroyed after the mechanical exfoliation. We infer that this phenomenon is closely related to the unique structure of layered OIHPs. Profited from the alternative arrangements of organic and inorganic layers along the staking axis direction, as well as the large difference of dielectric constant between these two moieties, the interlayer interaction between adjacent inorganic layers is weak [21,23], so that the layered OIHPs manifest weak dependence of optical properties on the layer number. In this sense, the TPA properties can be maintained during the mechanical exfoliation process, and the microcrystals can exhibit similar nonlinear-optics behavior to the bulk.
Aforementioned excellent crystal quality and intriguing TPA properties motivate us to explore the potential of IMPB for constructing TPA flexible photodetector with optoelectronic response on intense fs laser. The photodetector structure was designed as schematically plotted in Fig. 3(a), where the microcrystal of IMPB is on the top of a pair of gold electrodes, with the fs-laser beam incident from the back of the device onto the active photosensitive area. The photograph of the actual device is presented in Fig. 3(b). The interdigital electrodes (5 nm Cr/ 50 nm Au) were prepared on the polyethylene terephthalate (PET) substrate by the ultraviolet lithography and electron-beam evaporation procedure. The length and width of the finger are 100 and 10 µm, respectively, and each finger spacing is 9 µm. The microcrystal of IMPB was mechanically exfoliated with the aid of the scotch tape from bulk crystal, followed by transferring onto the electrodes with heat-release tape. The thickness of this microcrystal is determined to be ∼55 nm by AFM measurement (see Fig. S4 in Supplement 1), corresponding to 30 layers. The active area ($A$) of the device is estimated to be 1.8 × 10−6 cm2 as shown in the inset of Fig. 3(b).
Fig. 3. TPA photodetection of the IMPB photodetector. (a) Schematic device structure of this photodetector. (b) Photograph of the device. Inset: microscopic photograph of the channel area, where the area enclosed by the white dotted lines represents the channel material. (c) I-V curves measured under the different ${I_{\textrm{ex}}}$ (λex = 1000 nm). Inset: logarithmic plot of the photocurrent dependence on ${I_{\textrm{ex}}}$ (Vds = 6 V). The solid green dots are the experimental data, and the solid red line is the linear fitting curve. (d) Histogram for the slopes of the linear fitting curves at the different excitation wavelengths. (e) ${R_\textrm{p}}$ and ${D^\mathrm{\ast }}$ dependence on ${I_{\textrm{ex}}}$ (λex = 1000 nm and Vds = 6 V). (f) ${R_\textrm{p}}$ and ${D^\mathrm{\ast }}$ dependence on excitation wavelength (${I_{\textrm{ex}}}$ = 2.5 MW/cm2 and Vds = 6 V).
The TPA photodetection measurement was carried out by employing the aforementioned fs-laser source. The current-voltage (I-V) curves at varied ${I_{\textrm{ex}}}$ were measured at seven characteristic wavelengths as shown in Fig. 3(c) (λex = 1000 nm) and Fig. S5 in Supplement 1 (λex = 700-950 nm). For each excitation wavelength, one can see that the current increases monotonously with ${I_{\textrm{ex}}}$ at the fixed source-drain voltage (Vds) because more free carriers are generated at higher ${I_{\textrm{ex}}}$. Furthermore, the slopes (η) of the logarithmic plot for the photocurrent (${I_{\textrm{ph}}}$) dependence on ${I_{\textrm{ex}}}$ at seven wavelengths (the insets of Fig. 3(c) and Fig. S5 in Supplement 1) are all around 2 as summarized in Fig. 3(d), the same as the above-mentioned case for PL characteristics (Fig. 2(c)). It unambiguously proves that the photo-generated carriers and consequent photocurrent are originated from TPA effect. The saturation intensity of the device at λex = 1000 nm is larger than 3.8 MW/cm2, which is at least two orders of magnitude larger than the maximum peak intensity of the on-chip fs-pulse sources [1–4], suggesting that this TPA photodetector is applicable to integrated fs-laser systems.
To accurately evaluate the TPA photodetection performance, the responsivity (${R_\textrm{p}}$) related to the peak power of fs pulse is expressed as follows:
where $\tau $, f, and ${P_\textrm{a}}$ are the pulse duration, repetition rate, and average power of the fs laser, respectively. Accordingly, the detectivity (${D^\mathrm{\ast }}$) can be expressed as follows: where $q$ and ${I_\textrm{d}}$ are the elementary charge and dark current, respectively. Deduced from the experimental data in the insets of Fig. 3(c) and Fig. S5 in Supplement 1, the dependence of ${R_\textrm{p}}$ and ${D^\mathrm{\ast }}$ on ${I_{\textrm{ex}}}$ can be obtained as shown in Fig. 3(e) (λex = 1000 nm) and Fig. S6 in Supplement 1 (λex = 700-950 nm). Both ${R_\textrm{p}}\; $ and ${D^\mathrm{\ast }}$ increase monotonously with ${I_{\textrm{ex}}}$ at each wavelength, similar to the case of reported TPA photodetectors [5,6,8] that further proves the origin of photocurrent to be TPA process. The maximum ${R_\textrm{p}}$ is 21 and 5.5 nA/W at 700 and 1000 nm, respectively, corresponding to the ${D^\mathrm{\ast }}$ of 552.3 and 136.4 Jones. These ${R_\textrm{p}}$ values are one order of magnitude larger than that of the WS2/(C6H5C2H4NH3)2PbI4 vertical heterostructure photodetector (∼10−10 A/W at 800 nm) [54], and comparable with that of the CH3NH3Pb0.75Sn0.25I3 thin film photodetector (∼10−8 A/W at 1535 nm) [11]. In addition, as the excitation wavelength increases from 700 to 1000 nm (${I_{\textrm{ex}}}$ = 2.5 MW/cm2), ${R_\textrm{p}}$ decreases from 16.8 to 3.5 nA/W, meanwhile ${D^\mathrm{\ast }}$ decreases from 440.9 to 87.7 Jones (Fig. 3(f)). Such a phenomenon should be attributed to the decrease of TPA efficiency with the increase of excitation wavelength, consistent with the variation trend of TPA absorption coefficient with excitation wavelength as summarized in Fig. 2(f).The temporal photocurrent response and long-term stability are another important characters of the TPA IMPB photodetector. As shown in Fig. 4(a) (λex = 1000 nm) and Fig. S7 in Supplement 1 (λex = 700-950 nm), under periodic on/off of the fs-laser irradiation, this photodetector exhibits stable and reproducible photocurrent switching behavior at all the excitation wavelengths. The rise (τr) and decay time (τd) (defined as the time required to change the photocurrent from 10% (90%) to 90% (10%) of the peak value) are extracted to be 6.8 and 4.6 s, respectively (Fig. 4(b)). This relatively slow response time may be attributed to the large exciton binding energy (commonly on the order of several hundreds of meV) and strong electron-phonon coupling of layered OIHPs [55–59]. In this case, the separation of photo-generated excitons by the electric field of source-drain voltage is hindered and consequently, the generation of photocurrent is limited.
Fig. 4. Temporal and stability measurements for the IMPB photodetector. (a) The on/off switching cycles of photocurrent under periodic on/off of fs-laser irradiation (λex = 1000 nm, ${I_{\textrm{ex}}}$ = 2.43 MW/cm2, and Vds = 6 V). (b) The rise and decay time extracted from one on/off cycle. (c) The dependence of current on time under the irradiation of fs laser (λex = 1000 nm, ${I_{\textrm{ex}}}$ = 2.43 MW/cm2, and Vds = 6 V). (d) The on/off switching cycles of photocurrent for this photodetector before and after stored in the vacuum box for one month (λex = 1000 nm, ${I_{\textrm{ex}}}$ = 2.43 MW/cm2, and Vds = 6 V).
Additionally, we specifically performed both operational and long-term stability measurements. Under the irradiation of intense fs laser (λex = 1000 nm, $f$ = 80 MHz, $\tau $ = 120 fs, and ${I_{\textrm{ex}}}$ = 2.43 MW/cm2) for 90 min at ambient condition (23 °C and 55% humidity), the photocurrent can still maintain 91% of its initial value (Fig. 4(c)). This behavior indicates that, on one hand, the microcrystals of IMPB have good damage resistance to fs-laser irradiation; on the other hand, the heat effect generated by fs laser has subtle influence on the device performance. Besides, after stored in the vacuum box for one month, this photodetector can reproduce stable on/off current-switching behavior under the irradiation of fs laser (λex = 1000 nm and ${I_{\textrm{ex}}}$ = 2.43 MW/cm2), and its on-state current can maintain ∼89% of the initial value (Fig. 4(d)). Such excellent performance stability should be attributed to the crystal structure of layered OIHPs, where the organic and inorganic layers arrange alternatively along the staking axis, therefore the inorganic layers are efficiently isolated from vapour and oxygen thanks to the protection of hydrophobic organic layers [60]. The device stability may be further improved by encapsulating the perovskite microcrystals with some stable materials, such as silica film and boron nitride microsheet. For practical product, certainly, additional heat sink with fan or TEC cooling is more favorable to ensure long-term application.
To evaluate the capacity of mechanical flexibility and folding endurance of the IMPB photodetector, we bent it at varied angles with an adjustable spanner (corresponding to state I, II, III, IV, and V, as shown in Fig. 5(a)). As depicted in Fig. 5(b) (λex = 1000 nm) and Fig. S8 in Supplement 1 (λex = 700 and 850 nm), the I-V curves measured at the states I, III, and V manifest no obvious variation under different fs-laser wavelengths. Moreover, the current value is almost invariable with the bending angle (Fig. 5(c)), suggesting the outstanding stability and robustness of the IMPB photodetector. Figure 5(d) plots the photocurrent recorded during repeated bending of the device for 1000 cycles. Merely small attenuation is observed at the different wavelengths that the current can maintain 93%, 89%, and 86% of its initial value at λex = 700, 850, and 1000 nm, respectively. These excellent properties indicate the great potential of this flexible TPA photodetector in foldable optoelectronic devices designed for fs-laser measurement.
Fig. 5. Flexible photodetection measurement for the IMPB photodetector. (a) Photographs of this photodetector bent at the different angles. (b) I-V curves of this photodetector bent at three different angles (corresponding to state I, III, and V) under fs-laser irradiation (λex = 1000 nm and ${I_{\textrm{ex}}}$ = 2.27 MW/cm2). (c) The current (Vds = 6 V) under fs-laser irradiation (λex = 700, 850, and 1000 nm) variation with the bending state. (d) The current (Vds = 6 V) under fs-laser irradiation (λex = 700, 850, and 1000 nm) variation with the bending cycle when this photodetector was bent at a fixed angle (corresponding to state III).
4. Conclusions
In summary, the first (to our best) flexible photodetector based on the TPA effect was constructed with the layered hybrid perovskite IMPB. This device shows remarkable photodetection performance, including broad wavelength-response range (700-1000 nm), high saturation intensity (larger than 3.8 MW/cm2), high peak-power-related responsivity and detectivity (21 nA/W and 552.3 Jones at 700 nm; 5.5 nA/W and 136.4 Jones at 1000 nm), and superior current stability even after bending for 1000 times. This work may offer exciting possibilities for high-performance flexible optoelectronic devices aimed at direct detection of the fs-laser field.
Funding
Zhangjiang Laboratory (ZJSP21A001); Leading-edge technology Program of Natural Science Foundation of Jiangsu Province (BK20192001); Guangdong Major Project of Basic and Applied Basic Research (2020B0301030009); National Natural Science Foundation of China (11774161, 12334015, 62292523, 62375122, 92150302); National Key Research and Development Program of China (2019YFA0705004).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
Supplemental document
See Supplement 1 for supporting content.
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