In the era of information technology, the velocity at which data is generated, stored, and transmitted has reached an unprecedented pinnacle^[1−4]. Vast quantities of data can be generated in daily life. This information constitutes an important part of our personal and professional lives. However, with the exponential growth in data volume, effectively managing and processing this data securely and efficiently has emerged as an undeniable challenge. The concept of erasing information data after it has been accessed has become one of the pivotal methods for safeguarding data privacy and security^{[5, 6]}. After the data is accessed or read, by implementing measures in time to remove accessed or read data from storage media, not only effectively prevents unauthorized leakage but also provides additional security assurances for comprehensive lifecycle management of the data.

There are various technical methods available for achieving information destruction after reading, including physical destruction, data overwriting, utilization of specialized data erasure software, and other approaches^[7−12]. While ensuring data security, these technologies also put forward higher demands on data management, which need to find a balance between safeguarding data privacy and ensuring its availability. With the continuous progress of technology, the application scene of information destruction after reading is also expanding, from the data protection of personal devices, to enterprise-level data security management, and even national information security strategies, underscoring the growing significance of this concept^[13]. Therefore, with the continuous growth of data security demand, the technology of information destruction after reading will play a more critical role and become an important cornerstone for building a more secure and reliable information society^{[14, 15]}.

In the field of optical information processing, the characteristic of light as an information carrier presents unique advantage. Neuromorphic devices can realize synaptic functions by optical pulse modulation, including long-term potentiation and depression (LTP and LTD), short-term potentiation and depression (STP and STD) and so on. Ultrafast information processing can be also realized by the all-optical controlled reversible conductance modulation method^[16−19]. What’s more, the artificial synaptic devices could realize the efficient latent fingerprint information identification by in-sensor reservoir computing system under the deep ultraviolet light stimulation^{[16, 20]}. Numerous studies have demonstrated that high-speed and large-capacity data transmission can be achieved through optical−electric information coding and utilizing light as data carrier^[21−24]. Besides, by utilizing the coupling effect of the built-in electric field and ferroelectric polarization within the WSe₂/CIPS heterojunction interface, efficient regulation of photogenerated carriers in WSe₂ is achieved^[6]. A type of polarity-switchable optical encryption function is successfully constructed on a single device. However, the inability to prepare WSe₂/CIPS material in large areas by mechanical exfoliation and limited data protection capabilities severely limit application scope. Moreover, information acquisition is not involved. In the aspect of information security field, exploring how to utilize light for secure transmission and access remains a crucial ongoing topic. Based on ambipolar transistors, light is introduced and devices can possess the potential for positive and negative photoconductivity (PPC and NPC)^{[25, 26]}. This characteristic enables the conversion between PPC and NPC states by adjusting the polarity of the gate voltage, providing the possibility of realizing highly reconfigurable circuits and can handle various application scenarios flexibly^[27−29]. Leveraging this reconfigurable characteristic, light can be utilized for information encryption or destruction. Consequently, information is more difficult to be deciphered during transmission and reading, thereby enhancing communication security under the assistance of light.

Organic field-effect transistors (OFETs) exhibit promising application prospects in the domains of flexible electronics, luminescence, and sensors due to their inherent advantages in cost-effectiveness, solution processability, and large-area fabrication^[30−34]. The solution processability of OFETs confers significant benefits for scalable preparation and economical production on a large scale, which is crucial for widespread implementation and commercialization. Ambipolar organic transistors, which can simultaneously transport both holes and electrons, find extensive applications in various organic electronic devices, such as logic circuits, thermoelectric devices, and organic light-emitting transistors^[35−37]. Their ability to transport both types of charge carriers can simplify circuit design, reduce manufacturing processes, improve production efficiency, and lower the costs. The key factor in the development of high-performance ambipolar organic transistors lies in the careful selection of appropriate ambipolar organic semiconductors as channel materials. These ambipolar semiconductors can be obtained through a single layer, solution-processed hybrid and layer-by-layer assembly of unipolar n- and p-type organic semiconductors^[38−42]. Among these methods, solution−processed hybrid method offers distinct advantages over alternative methods, including simple process procedure, low fabrication cost, and high uniformity over a large area. Poly (3-hexylthiophene) (P3HT) is a cost-effective p-type semiconducting polymer that offers simplicity in synthesis at large scales, excellent optoelectronic performance, and the ability to be tailored through molecular structure modifications or combination with other materials for optimized performance in diverse applications. For example, the incorporation of synthesized CdSe nanocrystals with light harvesting properties in hybrid P3HT:CdSe photovoltaic devices enhances the efficiency of organic photovoltaic cells from 0.046% to 0.46% through surface ligand modification. Additionally, a higher power conversion 4.70% is achieved by employing a P3HT:SiNWs hybrid solar cell^{[43, 44]}. Poly[[N,N-bis(2-octyldodecyl)-napthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)] (N2200) is an n-type semiconductor material that exhibits a relatively high conductivity and possesses good charge transport characteristics^{[45, 46]}. Additionally, it demonstrates excellent chemical stability and solution processing capabilities, resulting in the formation of dense films^{[47, 48]}. These attributes are crucial for ensuring consistent performance and stability of the device. Utilizing the solution-processed hybrid method, a polymer mixture comprising P3HT and N2200 can be prepared for the development of high-performance organic ambipolar transistors. The P3HT/N2200 blends can broaden the absorption spectrum and bring more interfaces and possibilities for optoelectronic devices.

In this study, through solution-processed hybrid process, a reconfigurable P3HT/N2200 based ambipolar optoelectronic synaptic transistor for information security access was developed. Via optimizing the mass ratio of P3HT and N2200, the obtained transistor can achieve well-balanced electron and hole mobilities and relatively large ON/OFF ratio of 10³ in both n- and p-type regions. Due to its ambipolar behavior, the P3HT/N2200 based transistor exhibits both PPC and NPC under light illumination, particularly green light. The photo-generated carrier can be trapped by applying a gate voltage bias, enabling the emulation of common synaptic behaviors such as excitatory/inhibitory postsynaptic current (EPSC/IPSC) and transition from STP to LTP. Furthermore, the synaptic plasticity, including volatile/non-volatile and excitatory/inhibitory characteristics, can be effectively modulated through electrical and optical stimuli, highlighting its high reconfigurable nature. Moreover, leveraging these optoelectronic reconfigurable characteristics allows for the realization of capacity light assisted burn after reading, ensuring information security access. This work presents a paradigmatic solution for constructing a comprehensive and robust secure data transmission/access system.

Materials: P3HT and N2200 were purchased from Yuri Solar Co., Ltd. and Beijing Ogtek Technology Co., Ltd., respectively. Chromatographic grade chlorobenzene was purchased from Shanghai Rhawn Chemical Technology Co., Ltd. Silicon wafers were purchased from Suzhou Crystal Silicon Electronic and Technology Co., Ltd. All original materials and solvents were prepared without further purification.

Device Fabrication: The P3HT/N2200 based organic ambipolar optoelectronic synaptic transistors were fabricated by using Si/SiO₂ (100 nm oxide layer) wafer as substrate. The cleaning procedures for Si/SiO₂ wafer are as follows: ultrasonic cleaning with Decon-90 solutions for 20 min, ultrasonic rinsing three times (each time for 20 min) using deionized water, blow-drying with a nitrogen stream, drying in an oven at 90 ^oC for 40 min, and treatment with ultraviolet-ozone (UVO) for 15 min. The P3HT and N2200 polymers were dissolved in chlorobenzene in concentrations of 2.5 and 5.0 mg/ml, respectively. P3HT/N2200 mixed solution with ratios of 1 : 1, 1 : 2, and 1 : 3 was respectively prepared at a total blend system concentration of 7.5 mg/ml. After the sonication process for 15 min, the polymer mixture with different ratios were spin-coated on the Si/SiO₂ in a speed of 2000 rpm for 30 s. Moreover, the pure films of P3HT and N2200 were also fabricated. An annealing process (125 °C, 40 min) was conducted to facilitate effective condensation and densification of the blends. Then the 50 nm Au were deposited on the films through thermal evaporation as source and drain electrodes.

Characterization: The surface topography and potential of P3HT/N2200 were characterized by atomic force microscope (AFM) and Kelvin probe force microscopy (KPFM) (MDTC-EQ-M16-01, Bruker Dimension Inc.). The scanning electron microscope (SEM) image was obtained using a SEM (Carl Zeiss, Merlin Compact). UV−vis spectrum was recorded on Agilent cary 60. The electrical behaviors of optoelectronic synaptic transistors, such as current−voltage, and current−time curves, were measured in a MBRAUN glove box using a Keysight B2902A precision source/measure unit.

The P3HT/N2200 based organic ambipolar optoelectronic synaptic transistor array, single device structure, as well as molecular formulas of P3HT and N2200 are illustrated in Figs. 1(a)−1(c), respectively. Fig. 1(d) exhibits the schematic diagram of light assisted burn after reading. The process is as follows: after the information is written, it cannot be directly and accurately read by purely electrical means; correct access can only be achieved when light is simultaneously applied [Fig. 1(d) (ⅰ))]; once the light is removed following correct reading, the information is automatically erased to ensure data security [Fig. 1(d) (ⅱ)]. This light assisted burn after reading can be realized by P3HT/N2200 based transistor array [Fig. 1(e)], which was fabricated by using the simple solution-processed hybrid method. According to the UV−vis absorption spectrum in Fig. 1(f), the P3HT/N2200 mixture exhibits excellent photo response with the maximum absorption peak at 570 nm (green−yellow light area). The P3HT/N2200 mixture film exhibits high uniformity, as evidenced by the SEM image in Fig. 1(g), with 83-nm thickness, demonstrating the successful attainment of uniform film through the solution-processed hybrid method.

To optimize the device performance and achieve excellent ambipolar electrical behaviors, organic transistors based on P3HT/N2200 with different mass ratios (P3HT : N2200 = 1 : 1, 1 : 2, 1 : 3) were fabricated using spin coating and thermal evaporation techniques [Fig. 2(a)]. It is worth noting that the total mass concentration of P3HT and N2200 was maintained at 7.5 mg/mL to minimize variability. The vast majority of transistors exhibit unipolar electrical properties (only p- or n-type, e.g. P3HT and N2200 based transistors, Supplementary Fig. 1) and is able to migrate holes or electrons. Ambipolar transistors demonstrate the capability to integrate both p- and n-type electrical properties within a single device, enabling simultaneous electron and hole transmission as well as their accumulation in semiconductors. This feature endows ambipolar transport modulation with superior characteristics. Figs. 2(b)−2(d) describe the typical transfer curves of P3HT/N2200 based FETs with mass ratio of 1 : 1, 1 : 2, and 1 : 3. With the increase in the proportion of N2200, there was an elevation in electron carrier concentration and a gradual shift towards n-type polarity, resulting in a stronger p-type at a ratio of 1 : 1 and a stronger n-type at a ratio of 1 : 3. When the mixing ratios of P3HT/N2200 films are 1 : 1, 1 : 2, and 1 : 3, the hole/electron mobility are about 6.0 × 10⁻²/2.0 × 10⁻² cm²∙V⁻¹∙s⁻¹, 2.9 × 10⁻²/3.1 × 10⁻² cm²∙V⁻¹∙s⁻¹, 1.5 × 10⁻²/6.7 × 10⁻² cm²∙V⁻¹∙s⁻¹, respectively. Saturation mobilities were calculated according to the following equation:

1IDS=W2LμCi(VGS−Vth)2,

in which I_DS is source/drain current, L and W are the channel length and width, μ is the field-effect mobility of device, V_GS is source/gate voltage and the gate dielectric layer capacitance per unit area is represented in C_i.

Compared to the 1 : 1 and 1 : 3 ratios, P3HT/N2200 blends with a ratio of 1 : 2 exhibit relatively balanced electron and hole mobilities. Moreover, the ambipolar mobility is comparable to that of unipolar transistors, indicating simultaneous transport of both p- and n-channels. Additionally, the source−drain current (I_DS) increases proportionally with the absolute value of applied positive and negative gate voltages. Whereas P3HT/N2200 blends with 1 : 1 and 1 : 3 ratios show one side of the strong polarity (strong polarity: p and n for 1 : 1 and 1 : 3, respectively). In conclusion, we find diverse mixing ratios of P3HT/N2200 blends can induce transitions from unipolar to ambipolar transport, which provides a feasible approach to regulate molecular blends and further adjust electronic properties.

The blends fabricated by solution-processed hybrid method can achieve excellent ambipolar performance, and a good control of the blend morphology is crucial for achieving better electrical behaviors^[49]. Phase separation of polymer blends is a thermodynamic process, and for polymer blend solution system, the mixing ratio and interaction parameters determine the phase separation process and final film surface morphology. The solvent-polymer interaction parameters largely depend on the differential distinction in the solubility of the components. To decrease the solvent-polymer interaction, the chlorobenzene was chosen as cosolvent due to its excellent solubility to both P3HT and N2200. Based on AFM images of polymer mixture films in Figs. 2(e)−2(g) and pure polymers in Supplementary Figs. 1(c)−1(d), it is observed that despite exhibiting significant phase separation compared to individual P3HT and N2200, the polymer mixture films still demonstrate remarkable ambipolar characteristics. Additionally, there is minimal variation in surface topographies with an increase in N2200 mass ratio. Therefore, considering both electronic performance and surface topography, a ratio of 1 : 2 was selected for next investigation.

To comprehensively investigate the electrical performance of obtained blends [mass ratio: 1 : 2 (P3HT:N2200)], we conducted transfer curve measurements on the fabricated P3HT/N2200 based FETs with varying V_DS values, as depicted in Figs. 3(a) and 3(b). As shown in Fig. 3(a), under positive V_DS, the I_DS exhibits a subtle increase as the V_DS increases from 10−20 V, with an ON−state current of approximately 10⁻⁶ A and an OFF−state current of about 10⁻⁹ A, finally resulting in the decrease of ON/OFF ratio from 10³ to 10². Furthermore, a significant increase in I_DS current is observed under negative V_DS and as the V_DS increases from −10 to −20 V. In comparison to positive V_DS conditions, the device exhibits a relatively large OFF−state current and small ON−state current under negative V_DS, resulting in a low ON/OFF ratio. Therefore, we opted for positive V_DS for subsequent investigations into device performance due to the large ON/OFF ratio. The ambipolar transport modulation phenomenon of the P3HT/N2200 film is further confirmed by their corresponding output curves. The output currents of P3HT/N2200 based FETs exhibit a symmetrical feature and increase with an increasing gate bias, which indicates the ambipolar transport behavior of the device, as illustrated in Figs. 3(c) and 3(d).

In addition, the electrical synaptic functions of the P3HT/N2200 based transistors were also investigated, and the results are shown in Figs. 3(e) and 3(f). The gate electrode serves as a presynaptic neuron, adopting V_GS pulses as presynaptic input. The channel conductance can be served as the synaptic weight, whose value directly influence the information transmission between pre- and post-synaptic neurons. The channel conductance can be characterized by I_DS, which was measured by V_DS under the assistance of a read V_GS. In Fig. 3(e), as the amplitude of the V_GS pulse increases from −5 to −35 V while maintaining a duration of 0.1 s, I_DS (i.e. EPSC) deviates further from its original value and exhibits prolonged recovery times, transitioning from STP to LTP. Additionally, Fig. 3(f) demonstrates that when the device is stimulated by a positive V_GS spike ranging from 10 to 25 V for 0.1 s, I_DS (i.e. IPSC) decreases and remains at lower levels for extended periods before recovering to its initial value, thereby achieving STD to LTD. The programmable conductance with multiple states enables the regulation of synaptic weights, highlighting the potential utilization of P3HT/N2200 based transistors as artificial synapses.

According to Fig. 1(f), the P3HT/N2200 blend film exhibit wide light response from 350 to 850 nm, with three absorption peaks, 400, 570, and 710 nm. To comprehensively study the device photo-response properties, the electrical behaviors of P3HT/N2200 based FET under different wavelength (375, 520, and 637 nm) were investigated. As shown in Figs. 4(a)−4(c), with an increasing of light intensity, the I_DS exhibited a delicate increase in the hole-dominant region and a remarkable decrease in the electron-dominant region. This observation indicates distinct difference in current variation trends between the electron and hole-dominated states under light conditions. Specifically, in hole-dominant region, I_DS demonstrates a PPC characteristic under the light illumination. The photon number increases with increasing light intensity, and more photogenerated carriers (electron−hole pairs) are generated, resulting an increasing conductivity and PPC effect. An increasing light intensity may lead to accelerated migration of carriers. Within the electron-dominant region, electrons are captured by trapping center during the migration process, reducing the number of effective carriers participating in conduction. As a result, the conductivity decreases and the NPC effect is observed. Owing to the effects of PPC and NPC in different carrier-dominant regions, the current response of the P3HT/N2200 based organic ambipolar optoelectronic transistors can be significantly modulated by combining and tuning the means of photo and electric excitation, indicating the excellent reconfigurable characteristic. The gate voltage can be considered as a modulating signal that controls the strength or weight of synaptic connections. By applying different gate biases, we can simulate synaptic plasticity observed in biological systems. The transition between PPC and NPC provides a mechanism for regulating synaptic weight, which is crucial for information processing and storage. We investigated the response of the PSC to light pulses with varying wavelengths under different polarity conditions of V_GS. Prior to light stimulation, both the devices under negative and positive V_GS (−1 and 20 V) exhibited a relatively small I_DS. However, upon illumination, an enhanced transient photocurrent was generated by the device. Subsequently, after removing the illumination, distinct responses were observed for different polarity V_GS values. Specifically, when V_GS was −1 V, the PSC displayed a larger current compared to pre-illumination levels and exhibited noticeable short-term relaxation behavior [Figs. 4(g)−4(i)]. Conversely, at 20 V V_GS, the PSC showed a smaller current than before light exposure and demonstrated stable non-volatile behavior [Figs. 4(g)−4(i)]. Moreover, compare with other light wavelength, the green light (520 nm) can induce the most obvious current response, exhibiting the application potential for light assisted burn after reading.

Based on the optical response characteristics, photogenerated carrier transport process at P3HT/N2200−SiO₂ interface, and charge trapping behaviors, the device working mechanisms are proposed for elucidating the EPSC and IPSC behaviors obtained under light and different polarity V_GS. In the 0 V V_GS, electrons and holes are distributed on both sides of the semiconductor layer without gate bias [Fig. 5(a)]. Under the light condition, the photogenerated hole−electron pairs can increase the channel carrier concentration, resulting in the enhanced transient current [Figs. 4(d)−4(i)]. When the gate bias is negative, photogenerated holes are driven to the SiO₂−P3HT/N2200 interface, with a small portion of holes being trapped by defects at the SiO₂/channel interface [Fig. 5(b)]. Based on these conditions, when light is removed, the trapped holes are released, resulting in the increase of hole concentration and EPSC behavior. Additionally, due to the relatively low gate bias (−1 V), the holes may be only captured by shallow capture traps, resulting in the relatively short decay times (i.e., volatile behavior) [Figs. 4(d)−4(f)]. Conversely, when a large positive gate bias (20 V) is applied, a strong electric field promotes capturing of large amounts of electrons by deep trapping sites at the SiO₂/channel interface [Fig. 5(c)]. Upon removal of light under these conditions, trapped electrons produce shielding effects on gate bias and hinder transport of free electrons in channel. Thus, by tuning the gate bias amplitude and polarity, both the number and polarity of the trapped charge carriers can be modulated, finally leading to the difference in the transistor conductivity. The device corresponding energy band diagram is shown in Fig. 5(d), the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) are −3.0/−5.0 eV for P3HT, −3.8/−5.8 eV for N2200, respectively. Upon illumination, the electrons and the holes move and are trapped in SiO₂-P3HT/N2200 interface from the LUMO of N2200 and HOMO of P3HT, when positive and negative V_GS are applied, respectively.

The surface potential of P3HT/N2200 film under different optical/electrical conditions (light conditions: dark and light; gate bias: negative and positive) are studied by KPFM. Figs. 5(e) and 5(f) illustrate the surface potential of P3HT/N2200 film under V_GS of −10 V (e) and 10 V (f). Under the condition of −10 V V_GS, the surface potential values are 193 mV in the dark and 208 mV under green light, demonstrating hole capture [Fig. 5(e)]. With an applied voltage of 10 V V_GS, the surface potential values are 208 mV in the dark and 165 mV under green light, achieving electronic capture [Fig. 5(f)]. This variation in surface potential under different optical/electrical conditions is consistent with the aforementioned photo-assisted charge trapping behaviors.

In the realm of information, the increasing occurrences of data breaches and privacy infringements have heightened the demand for efficient and secure encryption technologies. Traditional encryption methods face challenges such as high computational complexity and susceptibility to attacks^{[50, 51]}. Recently, transistor technology based on optoelectronic effects has demonstrated significant potential in the field of information protection due to its distinctive physical properties^{[52, 53]}. In the common write and read mode [Figs. 6(a) and 6(b)], complete reading for information data is difficult due to subtle variations in response current magnitude. Furthermore, the reading information (although not entirely accurate) remains un-erased, posing a potential risk of information leakage. Taking advantage of reconfigurable characteristic of the P3HT/N2200 based organic ambipolar optoelectronic synaptic transistor, the light assisted burn after reading can be realized for information read and security access. As depicted in Fig. 6(c), image information is programmed using a one-to-one mapping mode, where each pixel corresponds to a single transistor device. The V_GS values for blue and gray pixels are set at 20 and −1 V, respectively. After the programming process, the information is read by pure electronic way (V_GS = − 1 and 20 V, V_DS = 15 V). For easy reading and differentiation, the response I_DS are divided into three levels according to the amplitude (<5.5 × 10⁻⁸ A, 5.5−8.5 × 10⁻⁸ A, >8.5 × 10⁻⁸ A). As shown in Fig. 6(b), it is evident that the pure electronic approach cannot accurately extract the programmed image information due to the small current. However, when the green light fully covers the information carrier Fig. 6(d), an increased photo-generated carrier concentration results in a sufficiently large transient response current for accurate extraction [Fig. 6(e)]. Furthermore, complete erasure of information occurs upon removal of light, enabling light assisted burn after reading and ensuring data security in Fig. 6(f). Partial reading of information is possible when only part of the information carrier is covered by green light [Fig. 6(g)]; this partial information that is presented may be sufficient for experienced individuals to recognize all details [Fig. 6(h)]. When the light is removed, the accessed information is automatically erased [Fig. 6(i)]. This partial access method for retrieving partial information not only ensures that experienced individuals obtain all relevant data but also prevents unauthorized access and enables simultaneous multiple reads, thereby providing an effective approach to achieving secure information access. Therefore, compared with common write and read, this light assisted burn after reading realized by P3HT/N2200 based organic ambipolar optoelectronic synaptic transistor has important application value in the field of information read and security access.

In this study, we fabricated a reconfigurable P3HT/N2200 based organic ambipolar optoelectronic synaptic transistor array for realizing information security access. Different V_GS modes drive distinct charge capture mechanisms, resulting in the manifestation of NPC and PPC effects. The ambipolar device exhibits reconfigurable excitatory/inhibitory electrical behavior under varying light conditions and polarity of V_GS, facilitating the mimicking of some common synaptic behaviors, including EPSC/IPSC and STP-LTP. Information can be encoded into the transistor array by manipulating different V_GS values, but reading current alone cannot provide complete information extraction. By applying light illumination to the device array, conductivity variations can be induced, enabling the accurate access for information. Upon removal of light exposure, the applied light-induced electron trapping enables immediate erasure of image information, thereby significantly enhancing data security. The ability to control information visibility through light exposure offers a dynamic and secure approach for data protection. This novel approach holds great promise for future advancements in data storage and secure communication.