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Abstract
Traditional strategies for self-powered devices face limitations in performance improvement due to the trade-off relationship between different parameters. Here, a new kind of ion-modulation self-powered photodetector is first proposed and fabricated by depositing superionic conductor RbAg4I5 on one side of monolayer graphene. The graphene homojunction is successfully formed at the boundary of the asymmetric structure due to the formation of bound states of ions and electrons at the contact interface. This kind of homojunction avoids the trade off between response parameters of traditional self-powered devices because the dissociation of bound states under light irradiation dominates the generation of a photocurrent. The experimental results indicate that the prepared photodetector can achieve great photo response with responsivity of 20 mA/W and a response speed of 700 µs for ultraviolet and visible light when no bias is applied, which is better than most existing graphene-based self-powered devices in single or overall parameters. Further, a semi-quantitative model is systematically established according to the internal mechanism and realizes a good consistency with experimental results. The work provides a new idea and offers the foundation to develop excellent self-powered devices based on superionic materials with good properties in controllability and modulation.
© 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Photodetector, as a kind of device that can convert light signal into electric signal [1], has been widely used in military and civilian fields such as ray measurement and detection, imaging, remote sensing and medical [2–6]. In recent years, under the demand for miniaturization and functionalization of devices, nanomaterials, especially two-dimensional (2D) layered materials, show great advantages and potentials in the preparation of new photodetectors due to their excellent photoelectric properties including light weight, small size and large light receiving surface area [7,8]. So far, photodetectors based on nanomaterials have been able to achieve absorption and detection of ultraviolet light, visible light, infrared light and terahertz light with the help of the difference in band gaps of different nanomaterials, such as the zero bandgap of graphene, narrow bandgap of black phosphorus, moderate bandgaps of transition metal dichalcogenides and the wide bandgap of insulating hexagonal boron nitride [9].
To date, already developed photodetectors based on 2D materials have shown remarkable photoelectrical performances in terms of detection waveband, responsivity, sensitivity and response speed. However, most photodetectors based on 2D materials need external power source to promote the directional movement of the photogenerated carrier to generate photocurrent, which increases the size of device and limits its practical application in a variety of negative complex environments. Subsequently, self-powered photodetector is designed and numerous researches are ongoing. Many types of self-powered photodetector have been successfully constructed with the deepening of research [10,11]. The photocurrent generation mechanisms of reported self-powered photodetector can be classified into two types. One is the photovoltaic effect including p-n junction and Schottky junction [12–14], which is related to the formation of junction, the excitation of free carriers as a result of optical transition and the separation of photogenerated carriers under the built-in electric field. The other is attributed to the thermal effect including the photothermoelectric effect [15,16], which convert photo-induced temperature change into electrical signals based on Seebeck effect. So far, the reported self-powered devices based on 2D materials are generally prepared by stacking different kinds of nanomaterials. Van der Waals heterojunction formed at the interface determines the photo-response process, but the transfer process of 2D materials inevitably introduces contaminants and bubbles at the interface, resulting in defects that influence the performance [17]. It is highly desirable to fabricate homogenous structure in a single 2D material. Besides, the current-response mechanism that relies on the light absorption of 2D materials to generate photogenerated carriers and separate them by the junction electric field has some shortcomings that hinder the improvement of performance. First, current devices generally obtain high gain by extending the carrier lifetime, thereby improving response sensitivity, but this is often at the expense of response speed; second, the response band of the device is limited by the band gap of the used material. By means of the superposition of multiple materials or converting light into heat, the response band can be broadened, but this often leads to an increase in the complexity of the device and a decrease in performance [18].
In order to solve the above-mentioned problems, optoelectronics based on ionic conductor have been developed due to the good characteristics of ions including controllable migration, high-efficiency regulation, and interaction with light and electric field [19–21]. Ionic conductor uses ions as carriers for signal transport, which is different from commonly used electronic conductors, generally including ionic liquids, ionic gels and superionic conductors. At present, the ionic conductors adopted in optoelectronics are mainly ionic liquid and ionic gel, which regulate the electric properties through the electric double layer formed at the interface when compositing with electronic conductors [22–24]. However, liquid properties of ionic liquid, and environmental pollution and poor stability of ionic gel, have many limitations in the development of photodetector and further practical applications. Therefore, more attention has been attracted at the exploration of superionic conductor for developing new photoelectrical devices. RbAg4I5, as the most representative superionic conductor, has an ionic conductivity that is comparable to that of electrolyte [25,26], is simple to prepare and easy to integrate, and has great value for the development of new high-performance photodetectors. The mobile silver ion in RbAg4I5 can effectively modulate the movement of carriers by formatting the bound states of ions and carriers, and the states can have a good response to the light irradiation [18,27]. So far, photodetector based on RbAg4I5 have been able to detect ultraviolet, visible and near-infrared light [18,27–30], but the large dark current exists due to the requirement of external power supply. The self-powered detection device based on superionic conductors has not been investigated.
Here, a novel self-powered photodetector with asymmetric structure is fabricated by compositing superionic conductor RbAg4I5 on the one side of monolayer graphene channel. At the interface of RbAg4I5 and graphene, the conducting carriers of graphene form bound states with the silver cations in RbAg4I5 and become localized, leading to the reduction of density of free carriers. The difference in carrier density pushes the formation of junction at the boundary of compositing graphene and pristine graphene, leading to the observation of asymmetric current-voltage (I-V) curve. The asymmetric I-V curve can be modulated by light illumination by affecting the barrier height, thus proving the existence and formation mechanism of the junction. Under the illumination of light, the bound carriers are dissociated and forms the directional movement under the drive of built-in electric field, resulting in the nonzero short-circuit current. The self-powered photodetection is achieved with responsivity of about 20 mA/W and response time constant of about 700 µs under the illumination of lasers. The dependence of the current response on the position of the laser irradiation is also explored, and the contribution of the migration of silver ion on the current response under irradiation is elucidated, which also enables the device to have a relatively large photodetection sensitive area except the junction area. Furtherly, a relatively complete semi-quantitative model including bound states of ions and carriers, dissociation of bound states and immigration of mobile silver ions, is established, which has good agreement with the experimental results.
2. Experimental
2.1 Fabrication of device
The CVD-grown monolayer graphene with a size of 15 cm × 10 cm on copper foil is obtained from XF NANO-Advanced Materials Supplier, and the graphene is pretreated by spin-coating with PMMA on the surface. The processes of wet-transfer of monolayer graphene onto SiO2/Si substrate are consistent with earlier published work. The SiO2 layer of substrate is about 300 nm thick. After transferring graphene, a pair of 60 nm thick gold electrodes are deposited on two sides of graphene with a gap of 1.5 mm, and then superionic conductor RbAg4I5 film is evaporated on the one side of graphene to form asymmetric compositing structure. The RbAg4I5 film with a thickness of 120 nm and a size of 0.75 mm × 2 mm is synthesized by evaporating a RbI and AgI mixture that is prepared by stirring and grinding two materials at a molar ratio of 1.5:8.5 for 4 h. The evaporation is achieved by a vacuum thermal evaporation method at a vacuum level of 10−3 Pa.
2.2 Material characterization and photoelectric measurements
Electronic measurements of device are measured by Source-Meter (Keithley 2400). Raman spectrums and atomic force microscope image are carried out with multifunctional and high resolution near-field optoelectronic and spectroscopic imaging microscope (Alpha 300RAS, WITec). The semiconductor lasers with wavelengths of 375 nm and 532 nm act as light source. The laser spots of 375-nm and 532-nm lasers are circles with diameters of about 2.5 mm and 2 mm respectively. The light power irradiating on the device is determined by light power meter (STARLAB, A: PD300-1W).
3. Results and discussion
In order to investigate the self-power photoelectric response based on composite film of superionic conductor and electronic conductor, the RbAg4I5 with the highest ionic conductivity and graphene with the highest electronic conductivity are selected to fabricate the device. The schematic diagram of the structure of the device is shown in Fig. 1(a). The CVD-grown monolayer graphene is transferred to the Si/SiO2 substrate by PMMA-assisted wet transfer method [31]. Superionic conductor RbAg4I5 is deposited on one side of graphene, forming an asymmetric structure. The transferred monolayer graphene is characterized by atomic force microscopy (AFM) as shown in Fig. 1(b). Figure 1(b) displays the change of height along the straight line shown in the inset, indicating that the height of transferred monolayer graphene is about 1.14 nm. The inset in Fig. 1(b) is the AFM image when the probe scans the boundary region of transferred monolayer graphene. The dark area is the substrate and the bright area is the graphene. Figure 1(c) displays the Raman spectra of pristine monolayer graphene and RbAg4I5/graphene composite film. The G peak at 1583 cm-1 and the 2D peak at 2686 cm-1 for two curves are obvious, with full width at half maximum (FWHM) values of 22 cm-1 and 38 cm-1 respectively, and these are characteristic peaks of graphene [32]. The intensity of the sharp 2D peak is roughly twice that of the G peak, which is a hallmark of monolayer graphene [33]. The D peak at around 1350 cm-1 that is associated structural defects originating from ripples of graphene and residual of PMMA [33], is present but not strong, indicating that the transferred graphene does not have major damage. As shown by the red curve, compared with that of pristine graphene in black curve, the Raman spectrum of RbAg4I5/graphene composite film has an evident fluorescence envelope, and the positons, FWHM and ratio of intensity of G band and 2D band have no significant change. The intensity map of peak area of 2D band is also measured for an area of 5 µm × 5 µm around the boundary region between RbAg4I5/graphene composite film and pristine graphene, as shown in Fig. 1(d). The white line shows the boundary of two regions. The envelope brought by the deposition of the superionic conductor increases the intensity of the Raman peak area, and the distribution of peak area intensity of 2D band have no drastic changes for the regions of RbAg4I5/graphene composite film and pristine graphene respectively, proving that the transferred graphene and composite film is flat and uniform without obvious damage.
Fig. 1. (a) Schematic diagram of the prepared device. Superionic conductor RbAg4I5 is deposited on one side of graphene to form asymmetrical structure. (b) AFM characterization of transferred monolayer graphene. The inset is scanning image at the edge of transferred graphene. The curve displays the change of height along the purple line in the inset. (c) Raman spectrum characterization of transferred graphene and fabricated of RbAg4I5/graphene composite film. (d) The Raman intensity map of peak area of 2D band around the boundary between RbAg4I5/graphene composite film and pristine graphene within 5 µm × 5 µm region. The white line displays the boundary.
The current-voltage (I-V) characteristics of prepared asymmetric device are measured in Fig. 2. In the Fig. 2(a), the black curve in the inset shows the linear electric behavior of pristine graphene, indicating the ohmic contact with electrode. After depositing superionic conductor, the conductance of graphene drops gradually due to the interaction of ions and carriers occurred at the interface of RbAg4I5 and graphene [27]. The device reaches a steady state after about 24 hours (Supplement 1, Fig. S1), and the conductance of prepared device is about 25% and 43% of that of pristine graphene at the voltage of -0.8 V and 0.8 V, indicating an asymmetric electrical characteristic, which can be attributed to the mechanism that the mobile silver ions of superionic conductor modulates the electrical properties of graphene. Some of the conduction electrons in the graphene are locally bound by silver ions in the superionic conductor due to the Coulomb interactions [27], resulting in the change of free carrier density and the movement of Fermi level of graphene, which forms a junction structure at the boundary between compositing graphene and pristine graphene. Different from p-n junction formed by element doping or electrostatic regulation, this junction is a homojunction formed by the local binding between ions and carriers, which has the potential to be actively modulated. When the applied voltage is too large, the bound state of carriers will be broken, and the voltage-current curve becomes linear as shown in Supplement 1, Fig. S2, proving that the ion regulation of superionic conductors is the main factor for the formation of the junction region, rather than from passive factors such as doping. This different junction formation mechanism provides a new mechanism and platform for carrier modulation and photoelectric response to break the existing trade-off balance between responsivity and response speed.
Fig. 2. The I-V characteristics of prepared device. (a) The I-V curves of asymmetric RbAg4I5/graphene composite film after depositing RbAg4I5 for 7 hours (red curve) and 24 hours (blue curve). The change of I-V curve reaches a stable state after 24 hours. The I-V curve of pristine graphene (black line) is shown in the inset. The silver ions in superionic conductors and carriers in graphene form bound states due to Coulomb interaction, reducing electrical conductivity and forming a junction region at the boundary between compositing graphene and pristine graphene, which results in asymmetrical positive and negative current. (b) The I-V curves of prepared device under illumination of 532-nm laser. The laser powers are 2 µW, 8 µW and 11 µW, respectively. The illumination position is at the boundary between compositing graphene and pristine graphene. The experimental data are fitted with Shockley equation. (c) The enlarged image of red boxed area in Fig. 2(b). The I-V curves do not cross the zero current or voltage point. The short-circuit current increases with the increase of laser power. (d) The extracted reverse saturation current IS from fitting is calculated with the function -lnIS which is negatively related with laser power. The red line is guiding line.
Figure 2(b) shows the I-V curve of fabricated device under the illumination of 532-nm laser. The illumination powers are 2 µW, 8 µW and 11 µW, respectively. The illumination position is at the boundary of compositing graphene and pristine graphene. The experimental curves of junction are fitted to the Shockley equation for quantitative analyses [34]. For a junction, the current expression can be written as
where the pre-exponential factor IS is the reverse saturation current; kB is the Boltzmann constant; T is temperature; q is the electron charge. The parameters n, RS, IL are introduced in the Shockley equation to fit the experimental data, these are ideality factor, series resistance and current associated with laser illumination. All the experimental points at four different laser powers can be well fitted, and extracted ideality factor n and series resistance RS of four curves are basically the same, 6 and 1.82 KΩ respectively, clearly proving that the properties of existing junction do not change greatly under the illumination of different laser power. The parameter IL is not equal to zero under the illumination of laser, and increases with the increase of laser power, as shown in Fig. 2(c) which is an enlarged view of red boxed area in Fig. 2(b). It can be seen that, under the illumination of laser, I-V curves do not cross the zero current/voltage point even when the applied voltage is zero. The observed nonzero open-circuit voltage and short-circuit current phenomenon is the unique feature of prepared homojunction as compared to photoconductive response, suggesting that the homojunction junction is capable of photovoltaic energy conversion without any external power input and consumption [17]. The reverse saturation current IS is mainly decided by barrier height for a junction when the factors such as junction area and temperature do not change.As shown in the Fig. 2(d), for the prepared device, the value of expression -lnIS linearly declines with the increase of laser power, indicating that the barrier height of formed junction is approximately proportional to the laser power and decreases with the increase of laser power. This is due to the dissociation of bound states of carriers and ions caused by illumination [27–30], which reduces the difference in carrier concentration and Fermi level between compositing graphene and pristine graphene. The dissociated carriers are driven by electric field to form current. The dissociated carriers will break the original equilibrium state of interaction between ions and electrons, and will reach a new equilibrium state after influencing barrier height. Different from photogenerated carriers that recombine in a short period of time, the concentration of dissociated carriers remains stable after reaching a new equilibrium. The built-in electric field at the boundary will always exist even under illumination due to the difference in carrier concentration, and thus the mechanism that drives the carriers to form the current will not be significantly affected. It indicates that the mechanism of ion regulation can get rid of the antagonistic relationship between the current response amplitude and response speed that limits the existing heterojunction devices.
The photoelectric responses of prepared device under illumination of 375-nm and 532-nm lasers are measured when no voltage is applied, as shown in Fig. 3. In Figs. 3(a) and (b), when laser irradiates at the boundary between compositing graphene and pristine graphene, obvious current generates. The nonzero short-circuit current is defined as Isc. The current Isc increases rapidly from zero, and reaches a saturation value in a short time. The saturation value of the current decreases slightly within the duration of laser irradiation for 375-nm and 532-nm lasers, which is caused by the desorption effect of graphene. The differences in amplitude is originates from the power density and photon energy. In the process of multiple cycles of light on and off, the current amplitude is basically the same, suggesting that the device has a good stability and repeatability of performance. For the illumination of 375-nm laser, at the laser powers are 2 µW, 9 µW and 16 µW, the observed currents Isc are 40 nA, 86 nA and 141 nA, respectively. For the 532-nm laser, at the laser powers are 4 µW, 15 µW and 20 µW, the observed currents Isc are 50 nA, 76 nA and 101 nA, respectively. The responsivity of device is defined as the ratio of current Isc to the irradiated laser power P. The observed maximum responsivities for 375-nm and 532-nm lasers are 20 mA/W and 12.5 mA/W. The difference in responsivity comes from the differences in photon energy. The dependences of current Isc on the power for 375-nm and 532-nm lasers are measured in Fig. 3(c). The current Isc gradually increases with the increase of power and gradually tends to be saturated.
Fig. 3. Photoelectric response characteristics of prepared device. The nonzero short-circuit current Isc is measured with light on and off when no voltage is applied. The periodic current response under illumination of (a) 375-nm laser and (b) 532-nm laser. (c) The dependence of current Isc on the irradiated laser power that is fitted with power function. (d) The transient rising and falling process of nonzero short-circuit current that is fitted with exponential function. The estimated time constants for rising and falling process are 1 ms and 0.7 ms, respectively. The device is illuminated by 532-nm laser.
The high-resolution transient response of current Isc is displayed in Fig. 3(d). The rising and falling processes can be fitted by the exponential function
where Ir and I0 are introduced parameters to descript the current amplitude, and τ is time constant to determine the response speed of current Isc. The extracted time constant τ1 for rising process is 1 ms, and the time constant τ2 for falling process is 700 µs. At the same time, the response speed can also be characterized based on the times at which the 90% increase and decrease of the observed current, and the times for rising process and falling process are 0.9 ms and 0.6 ms respectively. The values of Ir and I0 are-164.7 nA, 165.9 nA and 157.3 nA, -1.9 nA respectively for the rising and falling process. The performance of prepared device is better than some reported gated or doped-defined p-n junction [35–41], which can be seen in Tab. 1. However, the channel of reported device has to be tuned by gates or chemical doping, which is complicated for the device preparation and operation. The observed dynamic photocurrent switching without any electrical power consumption enables us to detect light irradiation and harvest light energy at a more efficient and facile manner. The response speed can be further improved by shorter graphene channel and faster carrier transport.
Table 1. Recently reported self-powered photodetectors based on 2D materials and their performance parameters.
Furtherly, for the prepared asymmetric self-power photodetector, an obvious dependence between current amplitude and laser irradiation position exists, as shown in Fig. 4, which is an alternative to achieve position sensing. Figure 4(a) shows a schematic diagram of the measurement setup. The irradiation position at the device is changed through the precise movement of the reflecting mirror. The boundary line between compositing graphene and pristine graphene is defined as the origin of the coordinate axis, and the direction of the coordinate axis is from the source to the drain. Figure 4(b) shows the current responses measured at different positions in 0.5 mm steps from -3 mm to 1 mm. The sign of the short-circuit current remains the same on both sides of the device. This indicates that the photothermoelectric effect would not contribute to the current response, because the sign of photocurrent would change with the move of irradiation position if photothermoelectric effect works.
Fig. 4. The dependence of short-circuit current on the irradiation position of laser. The 532-nm laser is adopted and the spot size is 2 mm in diameter. (a) The schematic diagram of the measuring setup. The reflecting mirror moves step by step under the control of the motor, so that the laser spot is irradiated at different positions of the prepared device. The boundary between compositing graphene and pristine graphene is chosen as the coordinate origin. (b) The short-circuit current response of prepared device when 532-nm laser is irradiated at different coordinate positions. For the composite part, when the distance is within 1 mm from the boundary, the amplitude decreases exponentially due to the Gaussian distribution of laser energy. When the distance from the boundary is greater than 1 mm, there is still an obvious photocurrent which has an approximately linear decrease.
The largest current response is obtained at the coordinate origin. For the part of RbAg4I5/graphene compositing film, the magnitude of the current response has a decline with the increase of the distance from the coordinate origin, and obvious current cannot be seen until the distance is up to 3 mm. However, for the part of pristine graphene, the current response drops very fast and reduces to zero after only 1 mm. This asymmetric relationship of current response magnitude versus position originates from the bounding effect of ions and carriers that dominates the photo response. The photo-excited carriers through graphene absorption can also contribute to the photocurrent, but the proportion is small.
Different from the observation on the pristine graphene, for the RbAg4I5/graphene compositing film, a photocurrent of about 10 nA can still be observed when the laser spot is moved to the position of -1.5 mm where laser would not influence the boundary at coordinate origin. Compared with the performance of pristine graphene, this response is not from the photoconductive effect of graphene, only suggests that the dissociation of bounded electrons and ions in the junction area can still be realized. According to previous studies, for the superionic conductors RbAg4I5, the light irradiation or gradient temperature having energies corresponding to the excitation of local stress leads to the reduction of activation energy, which give rise to diffusion flow of ions from irradiated or high-temperature region and the density of silver ions would decrease under the light irradiation or gradient temperature [42,43]. The number of bound electrons and the binding strength are proportional to the number of silver ions, so current can be observed if the junction between compositing graphene and pristine graphene is still in the affected area where the density of mobile silver cations can be reduced by light or temperature. The current amplitude is associated with the distance from the laser spot, and has a nearly linear decrease with the increase of distance for the responses at -3 mm, -2.5 mm, -2 mm and -1.5 mm.
A semi-quantitative model is presented to understand the basic mechanism of photoelectric behavior of prepared asymmetric device. In the device, graphene acts as the only channel for carrier transport, and silver ions in the superionic conductor regulate the carrier in the compositing part of graphene. As shown in the Fig. 5(a), electrons and ions would form bound states at the interface due to Coulomb interaction, and bound electrons become localized and the concentration of free carrier reduces [27]. At the boundary between compositing graphene and pristine graphene, due to the difference in carrier concentration, a built-in electric field and junction are formed. Due to the localization of electrons by ions, the number of free electrons in the composite region decreases, and the free electrons of uncomposite graphene move to the composite region under the drive of concentration difference, and the direction of built-in electric field is from the uncomposite region to the composite region. For the composting part, the density of free carriers can be expressed as:
where n0 is the density of graphene without RbAg4I5 film, nb is the density of localized carriers in the bound state, NAg is the density of silver cations, f is the fraction of carriers escaped from bound states, and C is a constant. The light irradiation, on the one hand, would dissociate the bound carriers, on the other hand, it would cause the decrease of the density of silver cations within the irradiation region by changing the activation energy for the diffusion of mobile silver cations [27,42]. When laser is irradiated on the prepared device, the density of free carries $n^{\prime} = {n_0} - n_b^{\prime}$, and the bound carriers is described as $n_b^{\prime} = C\cdot ({{N_{Ag}} - \Delta {N_{Ag}}} )\cdot ({1 - f - \Delta f} )$, so the current response is expressed as:Fig. 5. The analysis of physical mechanism and verification of semi-quantitative model with experimental data. (a) The schematic diagram of the formation of bound state and photo-response mechanism of the device. (b) The fitting of currents Isc at different laser powers. The dissociation of bound states between ions and carriers is main contribution of current when light is irradiated on the boundary of RbAg4I5/graphene compositing film and pristine graphene. (c) The fitting of current Isc at different illumination positions. The chosen laser illumination position has a distance larger than 1 mm, and thus the laser cannot illuminate the boundary. The immigration of silver ions due to temperature gradient induced by light illumination leads to the dissociation of bound carriers in junction area.
According to the established theory, for the prepared asymmetric device, when the light is illuminated on the boundary of composting graphene and pristine graphene, the short-circuit current of 375-nm and 532-nm lasers can be approximately descripted by the first part:
Furtherly, the induced temperature by the illumination has a linear relationship with position due to the theory of heat conduction, and thus the change of activation energy and the laser irradiation position approximately have a linear relationship, thus the experimental results in Fig. 4 can be well fitted with linear expression Eq. (9), as shown in Fig. 5(c).
4. Conclusions
In summary, we have demonstrated a new type of self-powered ion-modulated photodetector with asymmetric structure by compositing superionic conductor RbAg4I5 on the one side of monolayer graphene channel. Experimental observation results including asymmetric current-voltage curves and modulation of current-voltage curves under illumination, confirm the existence of homojunction at the boundary of compositing graphene and pristine graphene. The formation of the junction comes from the difference of carrier density due to the bound effect of ions on the carriers by Coulomb interaction. The light dissociates the bound carriers and the existence of a built-in electric field efficiently drive the directional movement of dissociated carriers without any external voltage. This kind of response mechanism avoids the trade-off relationship between response parameters that exists in general graphene-based device. The device shows a good self-powered current response with a responsivity of 20 mA/W and time constant of 700 µs at room temperature for ultraviolet and visible waveband, which is better than most reported self-powered device. Besides, the prepared device can generate a significant photocurrent in a relatively wide spatial range, which provides a larger photosensitive area than that of existing self-charging optoelectronic devices. The performance of device can be further improved by achieving the active control of bound states of ions and carriers. This first developed self-powered device based on two-dimensional materials and the modulation of superionic conductor offer a new method to develop high performance optoelectronic applications.
Funding
National Safety Academic Fund (U1730246); Education and Scientific Research Foundation for Young Teachers in Fujian Province (JAT200040); Natural Science Foundation of Fujian Province (2022J01540); the Starting Research Fund from the Fuzhou University (GXRC-21020); the Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics (KF201704, ZZ201703).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper may be obtained from the authors upon reasonable request.
Supplemental document
See Supplement 1 for supporting content.
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