Density Of Trap States Research Articles

Micro-Size Layers Evaluation of CIGSe Solar Cells on Flexible Substrates by Two-Segment Process Improved for Overall Efficiencies

This paper details the enhancement of the optoelectronic properties of Cu-(In, Ga)-Se2 (CIGSe) solar cells through a two-segment process in the ultraviolet (UV)–visible spectral range. These include fine-tuning the DC sputtering power of the absorber layer (ranging from 20 to 40 W at segment I) and thoroughly checking the trace micro-chemistry composition of the absorber layer (CdS, ZnO/CdS, ZnMgO/CdS, and ZnMgO at segment II). After segment I of treatment, the optimal 30 W CIGSe absorber layer (i.e., with a 0.95 CGI ratio) can be obtained, it can be seen that the Cu-rich film exhibits the ability to significantly promote grain growth and can effectively reduce its trap state density. After the segment II process aimed at replacing toxic CdS, the optimal metal alloy (Zn0.9Mg0.1O) composition (buffer layer) achieved the highest conversion efficiency (η) of 8.70%, also emphasizing its role in environmental protection. Especially within the tunable bandgap range (2.48–3.62 eV), the developed overall internal and external quantum efficiency (IQE/EQE) is significantly improved by 13.15% at shorter wavelengths. A photovoltaic (PV) module designed with nine optimal CIGSe cells demonstrated commendable stability. Variation remained within ±5% throughout the 60-day experiment. The PV modules in this study represent a breakthrough benchmark toward a significant advance in the scientific understanding of renewable energy. Furthermore, this research clearly promotes the practical application of PV modules, harmonizes with sustainable goals, and actively contributes to the creation of eco-friendly communities.

Surface Template Realizing Oriented Perovskites for Highly Efficient Solar Cells.

Formamidinium lead iodide (FAPbI3) perovskite films, ensuring optically active phase purity with uniform crystal orientation, are ideal for photovoltaic applications. However, the optically active α-FAPbI3 phase is easy to degrade into δ-phase due to numerous defects within randomly oriented films. Here, a "quasi-2D" perovskite template is pre-deposited on the film surface within the crystallization process based on the two-step preparation technology, which directly induced pure and highly orientated crystallization of α-FAPbI3 across the downward growth process. Furthermore, the enlarged interaction between 2D components with colloidal properties and lead iodide delayed the crystallization process effectively, yielding high crystallinity with low trap state density. The resulting perovskite photovoltaic devices exhibited a champion efficiency as high as 25.79% with comprehensively improved device stability. This work provides new insights into the utilization of 2D components and the formation mechanism behind 2D perovskites.

Enhancing open-circuit voltage in FAPbI3 perovskite solar cells via self-formation of coherent buried interface FAPbIxCl3-x.

The interfaces between the perovskite and charge-transporting layers typically exhibit high defect concentrations, which are the primary cause of open-circuit voltage loss. Passivating the interface between the perovskite and electron-transporting layer is particularly challenging due to the dissolution of surface treatment agents during the perovskite coating. In this study, a coherent FAPbIxCl3-x buried interface was simultaneously formed during the preparation of FAPbI3. This interlayer significantly improved charge extraction and transportation from the perovskite layer, while reducing trap state density. As a result, the open-circuit voltage increased from 1.01 V to 1.10 V, with the PCE improved from 19.05% to 22.89%.

Unlocking the Performance of Next-generation Non-volatile Capacitive Memory Devices with Ti-doped ZnO Nano Wires via Pulsed Laser Deposition

This paper investigates the impact of titanium (Ti) doping on zinc oxide (ZnO) nano wires (NWs) in non-volatile capacitive memory devices (NVCMDs) through fabrication and characterizations. ZnO NWs were fabricated using pulsed laser deposition (PLD), while Ti thin film (TF) was deposited via electron beam evaporation (e-beam). Field emission gun scanning electron microscopy (FEGSEM) confirmed the formation of ZnO NWs and Ti-doped ZnO NWs (Ti:ZnO NWs) on an n-type silicon (Si) substrates, with elemental compositions determined by energy dispersive X-ray spectroscopy (EDX). Structural characterization was conducted on the samples using high-resolution X-ray diffraction (HRXRD). Gold (Au) interdigitated electrodes (IDE) were employed to fabricate two distinct devices: Au IDE/ZnO NWs and Au IDE/Ti:ZnO NWs. Comparative analysis revealed that the Au IDE/Ti:ZnO NWs device exhibited a lower frequency dispersion fd value (0.025×109 F) compared to Au IDE/ZnO NWs device (0.029×109 F), indicating enhanced signal propagation due to Ti doping. The Au IDE/Ti:ZnO NWs device also demonstrated a high free charge carrier donor concentration ND value of 2.02×1012 /cm3, a significant trap concentration Nt value of 4.44×1011 /cm3 at an 8MHz frequency response. Additionally, it exhibited lower tangent loss (tan(δ)) value of 7430, maximum conductance Gmmax value of 13.40 mS, lower interface trap state density (ITSD) value of 2.05×1014 eV1 cm2, a maximum memory window (∆VMW) of 6.9V at ±15V, improved endurance, and superior data retention, making the Au IDE/Ti:ZnO NWs device a promising candidate for next-generation NVCMDs applications.

Nature of the carrier dynamics and contrast formation on the photoactive material surfaces: Insight from ultrafast imaging to DFT calculations.

Precise material design and surface engineering play a crucial role in enhancing the performance of optoelectronic devices. These efforts are undertaken to particularly control the optoelectronic properties and regulate charge carrier dynamics at the surface and interface. In this study, we used ultrafast scanning electron microscopy (USEM), which is a powerful and highly sensitive surface tool that provides unique information about the photoactive charge dynamics of material surfaces selectively and spontaneously in real time and space in high spatial and temporal resolution. Here, time-resolved images of CdTe (110), CdSe (100), GaAs (110), and other semiconductors revealed that the presence of oxide layers on the surface of materials leads to an increase in the work function (WF) and trap state densities upon optical excitation, leading to the formation of dark image contrast in USEM experiments. These findings were further supported by abinitio calculations, which confirmed the reliability of the observed changes in the excited surface WFs. Besides enhancing our understanding of surface charge dynamics, it also offers valuable insights into manipulating these properties. This study paves the way for precise control and the potential to design highly efficient light-harvesting devices.

Dual‐Sided Field Effect Passivation for Efficient and Stable Quasi‐2D Ruddlesden‐Popper Perovskite Photodetector

AbstractThe nonradiative recombination presented at the quasi‐2D (Q‐2D) Ruddlesden–Popper perovskite surface/interface limits the overall performance of perovskite photoelectric devices. Here, a dual‐sided field effect passivation (FEP) strategy to reduce nonradiative recombination is reported. By inserting high/low work function dielectric layers between perovskite layer and hole/electron transport layers, the trap state density of perovskite layer is effectively reduced, resulting in a longer carrier lifetime. Besides, the carrier dynamics and the synergistic mechanism of chemical passivation (CP) and FEP are clarified in detail. The interfacial polarization caused by the work function difference between different layers prevents Shockley–Read–Hall (SRH) recombination loss of photogenerated electrons/holes and improves interfacial charge transport. Benefiting from it, the passivated photodetector performance has been improved effectively, achieving a dark current of 9.62 × 10−11 A, a linear dynamic range (LDR) width of 171.4 dB, and an ultra‐fast response time low to 430 ns, which are currently the highest reported detection indicators in the Q‐2D perovskite photodetectors. In addition, the dual‐sided field effect passivated intercalation inhibits perovskite decomposition and greatly improves the environmental stability. In future, exploring the synergistic effect of FEP and CP materials for perovskite films is one of the development directions for studying efficient and stable perovskite photoelectric devices.

(Invited) Improving Interface Trap Analysis in Wide Band Gap MIS Structures

Modern power electronic technologies relevant to high power and fast switching applications are embracing wide bandgap (WBG) materials, including silicon carbide and gallium nitride (GaN), for their characteristically large breakdown electric field strengths and their comparatively high electron saturation velocities. However, WBG-based structures are known to exhibit unmitigated charge trapping due dangling bonds or impurities at or near the dielectric/semiconductor interface. Interface charge traps with energies near the band edge introduce threshold-voltage instabilities in metal-insulator-semiconductor (MIS) devices. Large densities of interface trap states and surface charges are also known to adversely alter the current response and channel transport dynamics in field effect transistor (FET) devices. Minimizing the density of these performance-degrading features, which are inherent to any MIS gate structure, remains a primary obstacle that prevents WBG-based technologies from realizing their theoretical potential in various application spaces.The complicated nuance of the numerous interface trap characterization techniques reported in literature have made comparing and communicating interface trap results in power electronics research a near-impossible task. As an example, the typical techniques used to characterize the density of interface states in silicon-based systems, such as the high-low method or the Terman method, are not suitable for WBG-based devices since they require unconventionally high probing frequencies to account for the fast trap states associated with WBG materials. Despite this readily proven fact, these techniques are still very popular in the WBG-based power electronics community, and an overwhelming majority of reported interface trap values are therefore unable to be thoughtfully discussed for the betterment of WBG-based technologies. Mitigating charge traps requires repeatable and physically accurate characterization techniques that follow a standard analysis protocol to correlate processing methods with device performance and reliability.Over the last decade, Sandia National Laboratories has made substantial contributions to the development of GaN power semiconductor devices and their characterization. In this talk, we will present recent work conducted at Sandia to develop a standardized procedure for determining interface trap state densities using quasi-static capacitance-voltage analysis in WBG-MIS-capacitor structures that produces repeatable and relatable results. Quasi-static methods that do not require frequency-based capacitance measurements, such as the - technique, have been suggested as a viable solution for determining the interface trap state densities in WBG systems. However, the results produced by the - technique are shown to be susceptible to errors in the analysis procedure and these errors were investigated in detail. These sources of error will be discussed, and we will present new strategies to greatly improve the accuracy of interface trap analysis measurements, including novel techniques to (1) calibrate the surface potential/gate voltage relationship and (2) measure the energy-dependence of capture cross sections. This collection of work greatly simplifies the interface trap analysis procedure and offers a solution to the present obstacle of reporting and comparing interface trap distributions in WBG-MIS structures. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Low-frequency noise analysis on asymmetric damage and self-recovery behaviors of ZnSnO thin-film transistors under hot carrier stress

The need for understanding the low-frequency noise (LFN) of metal oxide semiconductor thin-film transistors (TFTs) is increasing owing to the substantial effects of LFN in various circuit applications. A focal point of inquiry pertains to the examination of LFN amidst bias stress conditions, known to compromise TFT reliability. In this study, we investigate the effects of hot carrier stress (HCS) on zinc tin oxide (ZTO) TFTs by low-frequency noise (LFN) analysis. Asymmetric damage caused by HCS is analyzed by measuring the power spectral density at the source and drain sides. The excess noise generated by the HCS is analyzed with consideration of trap density of states (DOS). It is revealed that the needle defects are generated during the HCS, significantly affecting the LFN characteristics of the ZTO TFTs. Additionally, we observe a self-recovery behavior in the devices and demonstrate the relevant changes in the LFN characteristics following this phenomenon. This study provides valuable insights into the LFN characteristics of ZTO TFTs under HCS conditions and sheds light on the underlying mechanisms.

Effect of substrate temperature on the performance of Sb2Se3 thin film solar cells fabricated by chemical-molecular beam deposition method

Antimony triselenide (Sb2Se3) stands as a promising candidate for photovoltaic (PV) applications due to its favorable material- and optoelectronic properties. However, the realization of further advancements in device efficiency is hindered by the substantial deficit in open-circuit voltage (VOC) attributed to the presence of multiple defect states and detrimental recombination losses.In this work, solar cells based on Sb2Se3 absorber layers deposited by chemical-molecular beam deposition method at substrate temperatures of 400 °C, 450 °C, and 500 °C. Due to the precise control of the Sb/Se ratio, Sb2Se3 thin films with stoichiometric composition were obtained, which was confirmed by energy-dispersive X-ray spectroscopy. The effect of substrate temperature on the morphology and electrical properties of Sb2Se3 thin-films were characterized by scanning electron microscopy and hot probe method. The PV performance of Mo/Sb2Se3/ZnCdS/CdS/ZnO/ITO/Au devices were investigated by current-voltage characteristics, and external quantum efficiency. The conductivity values tend to increase from 1.2 × 10–6 to 4.6 × 10–4 (Ω cm)-1 as the substrate temperature increased. Whereas, the trap-state density was determined between 7.3 × 1013 – 1.7 × 1014 cm-3 in the absorber layer by the space charge limited current method. Ultimatety, it has been shown that defect densities in Sb2Se3 films can be suppressed to some extent by optimizing the substrate temperature. Best solar cell performance of 5.36%, resulting from VOC of 476 mV, short-circuit current densit of 22.97 mA/cm−2, and fill factor of 49% at the substrate temperature of 450 °C.

High-Temperature Characterization of AlGaN Channel High Electron Mobility Transistor Based on Silicon Substrate.

In this paper, it is demonstrated that the AlGaN high electron mobility transistor (HEMT) based on silicon wafer exhibits excellent high-temperature performance. First, the output characteristics show that the ratio of on-resistance (RON) only reaches 1.55 when the working temperature increases from 25 °C to 150 °C. This increase in RON is caused by a reduction in optical phonon scattering-limited mobility (μOP) in the AlGaN material. Moreover, the device also displays great high-performance stability in that the variation of the threshold voltage (ΔVTH) is only 0.1 V, and the off-state leakage current (ID,off-state) is simply increased from 2.87 × 10-5 to 1.85 × 10-4 mA/mm, under the operating temperature variation from 25 °C to 200 °C. It is found that the two trap states are induced at high temperatures, and the trap state densities (DT) of 4.09 × 1012~5.95 × 1012 and 7.58 × 1012~1.53 × 1013 cm-2 eV-1 are located at ET in a range of 0.46~0.48 eV and 0.57~0.61 eV, respectively, which lead to the slight performance degeneration of AlGaN HEMT. Therefore, this work provides experimental and theoretical evidence of AlGaN HEMT for high-temperature applications, pushing the development of ultra-wide gap semiconductors greatly.

Nonhalogenated Solvent-Processed Efficient Ternary All-Polymer Solar Cells Enabled by the Introduction of a Naphthyloxy Group into the Side Chain of Polymer Donors.

Conjugated polymer donors are crucial for enhancing the power conversion efficiencies (PCEs) in all-polymer solar cells (All-PSCs) in nonhalogenated solvents. In this work, three wide-band-gap polymer donors (Sil-D1, Ph-Sil-D1, and Nap-Sil-D1) based on dithienobenzothiadiazole (DTBT) and benzodithiophene (BDT) donor moieties optimized by side chain engineering were designed and synthesized. Alkyl (Sil-D1), phenyloxy (Ph-Sil-D1), and naphthyloxy (Nap-Sil-D1) alkyl siloxane side chain units were incorporated into these polymer donors, respectively. Notably, the Nap-Sil-D1 polymer donor had a greater conjugation length, π-electron delocalization, and improved dipole moment. The deepest highest occupied molecular orbital level of Nap-Sil-D1, with a high absorption coefficient, showed better aggregation properties. In addition, reduced bimolecular recombination and trap-state density generated a high charge transfer to cause a significant enhancement of open-circuit voltage, current density, and fill factor values of 0.94 V, 25.5 mA/cm2, and 70.4%, respectively, for the Nap-Sil-D1-blended All-PSC ternary device (PM6:Nap-Sil-D1:PY-IT), with the highest PCE of 16.8% in the o-xylene solvent, compared to other polymers (Sil-D1 and Ph-Sil-D1) with PCEs of 15.5 and 16.2%. As a result, this optimized device architecture was found to be the most promising as a nonhalogenated solvent processed in additive-free ternary All-PSCs with good stability.

Enhanced charge carrier transport and defects mitigation of passivation layer for efficient perovskite solar cells

Surface passivation has been developed as an effective strategy to reduce trap-state density and suppress non-radiation recombination process in perovskite solar cells. However, passivation agents usually own poor conductivity and hold negative impact on the charge carrier transport in device. Here, we report a binary and synergistical post-treatment method by blending 4-tert-butyl-benzylammonium iodide with phenylpropylammonium iodide and spin-coating on perovskite surface to form passivation layer. The binary and synergistical post-treated films show enhanced crystallinity and improved molecular packing as well as better energy band alignment, benefiting for the hole extraction and transfer. Moreover, the surface defects are further passivated compared with unary passivation. Based on the strategy, a record-certified quasi-steady power conversion efficiency of 26.0% perovskite solar cells is achieved. The devices could maintain 81% of initial efficiency after 450 h maximum power point tracking.

Small molecule of aminoacetonitrile hydrochloride prompting large improvement in the performance of perovskite solar cells

Perovskite solar cells (PSCs) continuously update their best research efficiency records, currently has exceeded 26 %. However, the industrialization of PSCs still faces the issues of stability and performance improvement, and interface defects are notorious negative factors. Herein, a small molecule aminoacetonitrile hydrochloride (AAN) as multi-functional additive is introduced into the interface of tin oxide (SnO2)/perovskite. The cyano group (CN) on AAN can coordinate with Pb2+ on perovskite; Cl− can occupy halide vacancy in perovskite and oxygen vacancy on SnO2, and NH3+ can form hydrogen bonding with iodide ions in perovskite. It is verified that crystal growth quality is improved, trap-state density is reduced, energetic alignment is adjusted, charge transfer is ameliorated, and carrier recombination is alleviated. Therefore, the AAN-modified PSC achieves a maximum power conversion efficiency of 24.52 % with a high open-circuit voltage of 1.18 V and satisfactory stability, compared to the unmodified device efficiency of 21.24 %, demonstrating a significant impact of the multi-functional small molecule of AAN in highly efficient and stable PSCs.

High-Performance CsPbI3 Quantum Dot Photodetector with a Vertical Structure Based on the Frenkel-Poole Emission Effect.

The selection of photoactive materials and the design of device structures are critical to the photoelectronic performance of photodetectors. This study reports on a vertically structured photodetector device with rapid, stable, and efficient photoelectric performance across the UV-visible broadband range based on the Si++/SiO2/Au/single-layer graphene/CsPbI3 quantum dots (QDs) configuration. In this specific device structure, a relatively high conductivity Si++/SiO2 wafer was used as the substrate, a CsPbI3 QD film with high light absorption was used as the photoactive layer, and a monolayer graphene with high conductivity was inserted between the substrate and the CsPbI3 QD film to form a heterojunction with the QD film. Based on the Frenkel-Poole emission effect arising from the high trap state density within the SiO2 layer, the device exhibited excellent photoelectric performances. Especially at a wavelength of 365 nm, a photocurrent responsivity of 2319 A/W, a specific detectivity of 1.15 × 1014 Jones, an external quantum efficiency of 7883%, and an on/off time of 39/36 ms at a Si++ terminal voltage of -80 V and an optical power density of 84.03 nW/cm2 can be achieved.

Enhanced device performance of GaN high electron mobility transistors with in situ crystalline SiN cap layer

In this paper, a ∼2 nm in situ SiN cap layer on AlGaN barrier layer is grown, which is revealed to be crystalline using high-resolution cross-sectional transmission electron microscopy. Benefitting from superior interface quality of epitaxial crystalline SiN/AlGaN interface, the gate diodes with in situ SiN cap layer feature lower interface trap state density than that with GaN cap layer. By comparing the GaN high electron mobility transistors (HEMTs) with the conventional GaN cap layer, the GaN HEMTs with in situ SiN cap layer exhibit improved device performance, showing higher electron mobility, higher drain current, larger on/off current ratio, and higher transconductance. For breakdown characteristics, the devices with in situ crystalline SiN cap layer show prominent advantages over the GaN cap layer with a 30% breakdown voltage increase to 810 V.

Multifunctional Acetaminophen Interlayer for High Efficiency and Durability Lead-Lean Perovskite Solar Cells.

Due to the easy oxidation of Sn2+, which leads to form tin vacancy defects and poor perovskite film quality, caused by the rapid crystallization rate in tin-based perovskite solar cells (PSCs), their efficiency lags far behind that of lead-based PSCs. To improve the photovoltaic (PV) performance and stability of FA0.9PEA0.1SnI3-based PSCs (T-PSCs), a small amount of Pb(SCN)2 is introduced into a perovskite precursor as an antioxidant, and acetaminophen (ACE) with various functional groups is used to modify a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/perovskite interface. The results show that the Pb(SCN)2 additive and ACE interfacial modification can not only optimize energy level alignment in T-PSCs but also inhibit Sn2+ oxidation to reduce the trap-state density, resulting in promoted carrier transport. The synergetic effect of the Pb(SCN)2 antioxidant and ACE interfacial modification significantly reduces nonradiative recombination and improves the PV performance and stability of T-PSCs. Consequently, the unsealed T-PSCs with the Pb(SCN)2 additive and ACE modification achieve a champion efficiency of 12.04% and maintain 99% of their initial PCE after being stored in N2 for more than 2100 h, while reference T-PSCs demonstrate a champion PCE of 6.20% and retain only 72% of its initial PCE. Moreover, the modified T-PSCs without encapsulation demonstrate much better stability in humid air.

Tailoring Interfacial Dipole Molecules to Mitigate Carrier and Energy Losses in Perovskite Solar Cells

AbstractInterface engineering has become the mainstream for improving the performance of perovskite solar cells (PSCs). Interfacial dipole (ID) molecules have emerged as a feasible and effective strategy to alleviate the charge carrier loss and energy loss in PSCs. Here, the three symmetrical donor–acceptor interfacial dipole molecules (named PzT, PzTE, and PzTN) are designed and synthesized with identical hole transport backbone and different anchoring groups. The ID molecule is introduced into the interface between the perovskite layer and the hole transport layer. The dipole moments of ID molecules regulate the surface work function and energy‐level alignment of perovskites, improve charge extraction, and reduce energy loss at the interface. Meanwhile, the anchoring groups of ID molecules coordinate with the defects on the surface of PVK and HTL, reduce interfacial trap state density and charge accumulation, and mitigate the carrier non‐radiative recombination losses. As a result, PzTN‐modified PSC achieved a champion power conversion efficiency of 25.34% with a photovoltage of 1.176 V and a fill factor (FF) of 83.27%, accompanied by almost undetectable hysteresis and excellent operating stability. This research demonstrates a feasible strategy for efficient and stable PSCs by interfacial dipole molecules.

Flexible Near‐Infrared Organic Photodetectors With Ultralow Dark Current by Layer‐by‐Layer Blade Coating

AbstractNear‐infrared organic photodetector (NIR OPD) is promising for emerging wearable biosensing applications. However, their practical application is hindered by the high dark currents of devices that limit the detection of faint light. In this work, highly sensitive flexible NIR OPDs are presented with ultralow dark currents, fabricated using a layer‐by‐layer blade coating (LBL‐BC) technique. In the active layer, a fully fused‐ring molecule FM2, featuring a fixed molecular skeleton, is employed as an electron acceptor to reduce the trap density. The LBL‐BC method enhances the film order and phase purity of the active layer, significantly reduces the trap density of states, and optimizes the vertical phase separation structure of the thin film, thereby preventing reverse charge injection. As a result, a highly sensitive flexible NIR OPD is developed exhibiting an ultralow dark current density of 4.83 × 10−9 A cm−2 at −0.3 V bias and an extremely low noise current density of 7.65 × 10−15 A Hz−1/2 at 10 Hz, comparable to commercial silicon photodiodes. Furthermore, this flexible device is successfully applied for real‐time monitoring of human heartbeat rate, oxygen saturation, and motion recognition. These findings advance the development of highly sensitive NIR OPDs and their application in wearable biosensing technologies.

Bilayer interface engineering through 2D/3D perovskite and surface dipole for inverted perovskite solar modules

The persistency of passivation and scalable uniformity are vital issues that limit the improvement of performance and stability of large-area perovskite solar modules (PSMs). Here, we design a bilayer interface engineering strategy that takes advantage of the stability and passivation ability of low-dimensional perovskite and the dipole layer. Introducing phenethylammonium iodide (PEAI) can form 2D/3D heterojunctions on the perovskite surface and effectively passivate defects of perovskite film. Interestingly, the upper piperazinium iodide (PI) layer can still form surface dipoles on the 2D/3D perovskite surface to optimize energy-level alignment. Moreover, the bilayer interface engineering enables large-area perovskite films with uniform surface morphology, lower trap-state density and stability against environmental stress factors. The final devices achieved a small-area PCE of 25.20% and a large-area (1 ​cm2) PCE of 23.96%. A perovskite mini-module (5 ​× ​5 ​cm2 with an active area of 14.28 ​cm2) could also be fabricated to achieve a PCE of 23.19%, ranking it among the highest for inverted PSMs. Additionally, the device could retain over 93% of its initial efficiency after MPP tracking at 45 ​°C for 1280 ​h. This study successfully demonstrates a bilayer interface engineering with respective functions, offering valuable insights for producing efficient and stable large-area PSCs.

Emulating Low-Power Synaptic Plasticity in a Solution-Processed Oxide-Based Long Retention Memory Transistor with High Learning Accuracy.

The exploration of synaptic plasticity in metal-oxide-based ferroelectric thin-film transistors has been limited. As a perovskite ferroelectric material, LiNbO3 is widely studied; but its potential use as a neuromorphic device, like synaptic transistors, has not been realized. In this study, a solution-processed ferroelectric thin-film transistor (FeTFT) with an alternating layer of LiNbO3 and Li5AlO4 as a gate dielectric has been fabricated. This configuration reduces the depolarization field by leveraging the large ionic polarization of Li+ ions in the Li5AlO4 layer, while the wide bandgap helps mitigate the leakage current. FeTFT exhibits impressive transistor performance, including a saturation mobility of 0.478 cm2V-1 s-1, an on/off ratio of 3.08 × 103, and a low trap-state density of 1.3 × 1013 cm-2. Moreover, the device demonstrates good memory retention, retaining information for nearly 1 day. It successfully emulates synaptic plasticity, specifically short-term plasticity and long-term plasticity. Besides, a 94% training accuracy has been achieved through artificial neural network simulation. Notably, the FeTFT consumes minimal power, with energy consumption of approximately 3.09 nJ per synaptic event, which is remarkably low compared to other reported solution-processed FeTFT devices.