Role In Device Operation Research Articles

Interface-Centric Strategies in Kesterite Solar Cells: Addressing Challenges, solutions, and Future Directions for Efficient Solar-Harvesting Technologies.

As reserves of non-renewable energy sources decline, the search for sustainable alternatives becomes increasingly critical. Next-generation energy materials play a key role in this quest by enabling the manipulation of properties for effective energy solutions and understanding interfaces to enhance energy yield. Studying these interfaces is essential for managing charge transport in optoelectronic devices, yet it presents significant challenges. This review emphasizes the critical role of interfaces in kesterite solar cells (KSCs), focusing on interfacial architecture, carrier losses, and non-radiative recombination. This review highlights the importance of addressing interface issues and utilizing advanced characterization tools to reveal interface properties. Current interface problems are addressed, recent advancements in interface engineering are summarized, and perspectives on future challenges and prospects are offered. The goal is to illuminate the nature of interfaces and tackle interface losses, which are crucial for improving device design and performance. Despite their pivotal role in device operation, comprehensive reviews on interfaces are lacking, underscoring the relevance of the work for researchers in material interfaces and device engineering. It is hoped that this article will spark interest and inspire further research into interface studies and the mitigation of interface losses.

Multifilamentary switching of Cu/SiOx memristive devices with a Ge-implanted a-Si underlayer for analog synaptic devices

Various memristive devices have been proposed for use in neuromorphic computing systems as artificial synapses. Analog synaptic devices with linear conductance updates during training are efficiently essential to train neural networks. Although many different analog memristors have been proposed, a more reliable approach to implement analog synaptic devices is needed. In this study, we propose the memristor of a Cu/SiOx/implanted a-SiGex/p++ c-Si structure containing an a-Si layer with properly controlled conductance through Ge implantation. The a-SiGex layer plays a multifunctional role in device operation by limiting the current overshoot, confining the heat generated during operation and preventing the silicide formation reaction between the active metal (Cu) and the Si bottom electrode. Thus, the a-SiGex interface layer enables the formation of multi-weak filaments and induces analog switching behaviors. The TEM observation shows that the insertion of the a-SiGex layer between SiOx and c-Si remarkably suppresses the formation of copper silicide, and reliable set/reset operations are secured. The origin of the analog switching behaviors is discussed by analyzing current-voltage characteristics and electron microscopy images. Finally, the memristive-neural network simulations show that our developed memristive devices provide high learning accuracy and are promising in future neuromorphic computing hardware.

Electron and Neutron Beam Irradiation Effects in Homogeneous and Nanostructured Oxides.

Oxide-based materials have a variety of applications in chemical sensing and photocatalysis, thin-film transistors, complex-oxide field-effect transistors, nonvolatile memories, resistive switching, energy conversion, topological oxide electronics, and many others. The radiation resistance of these materials in such devices plays an important role in device operation in radiation environment, and this attracts much attention in the research area. In spite of damage in a number of cases high-energy particles may have a beneficial effect on the target. In this mini-review article examples of both creation of defects and beneficial changes in the structure and properties of homogeneous and nanostructured oxides caused by high-energy electron and neutron irradiation are given by considering some recently published results. First, the attention is turned to ionizing and displacement effects of electron and neutron irradiation in homogeneous bulk and thin-film oxides reported in the literature. Then, the effect of electron and neutron irradiation on nanostructured oxides and semiconductor nanoparticles embedded in an oxide matrix is regarded. Considerable attention is paid to silicon oxide layers since they are widely used in microelectronic products, which are among the most manufactured devices in human history. Processes of irradiation-induced lattice rearrangement, compositional changes, growth of nanoparticles and their size reduction, creation of point defects and their complexes, electron-hole generation, and charge trapping are discussed.

High‐Performance Polymer Photodetectors using ZnO Nanocrystal Trap States

A metal oxide interfacial layer is introduced into polymer photodetectors (PPDs) to achieve low dark current and high photocurrent. Although the defects of the metal oxide play a key role in device operation, defect effects on PPDs are poorly understood. Herein, PPDs using nanoparticle (NP) and amorphous zinc oxide (ZnO) films as the indium tin oxide (ITO) modification layer are realized and characterized, and the former device shows high performance in every figure of merit: external quantum efficiency of 1980%, detectivity of 1.03×1014 Jones, responsivity of 9.51 A W−1, response time of ≈10 μs, and linear dynamic range of over 100 dB at a low reverse bias. The comparison of the NP ZnO and amorphous ZnO‐based devices and the ultraviolet (UV) light illumination effect on the devices imply the underlying operation mechanism. The surface defects in the ZnO NPs efficiently block external charge injection, whereas the defect‐induced photogenerated charge accumulation at the interface between the ZnO layer and the active layer leads to a tunneling current under illumination. This methodology provides universal guidance for fabricating high‐performance PPDs based on a metal oxide interfacial layer.

Effects of processing additives in non-fullerene organic bulk heterojunction solar cells with efficiency >11%

Here we investigate processing additive-dependent photovoltaic performance and charge recombination in organic bulk heterojunction (BHJ) solar cells based on a polymeric donor of PBDB-T blended with a non-fullerene acceptor m-ITIC. We find that PBDB-T:m-ITIC solar cells exhibit good compatibilities with the utilized additives (DIO, CN, DPE, and NMP) in optimal conditions, can have a high charge dissociation probability approaching 100% (with DIO), leading to ultimate efficiency >11%. Regardless of additives, we observe a dominant 1st order monomolecular recombination with insignificant bi-molecular recombination or space-charge effects in these solar cells. Despite of impressive power conversion efficiency (PCE), it is of surprise that Shockley-Read-Hall recombination is identified to play a role in device operation. Thus, it points to the necessity to mitigate the influences of traps to further boost the efficiency in non-fullerene based organic solar cells.

(Keynote) Multiscale Modeling of Polymer-Electrolyte-Fuel-Cell Components

Water management in proton-exchange membrane fuel cells plays an important role in device operation, especially at lower temperatures where liquid water exists. Key to understanding water management is determining the mechanisms of water movement through the various fuel-cell components. Traditionally, continuum-scale mathematical modeling has been used to optimize and understand fuel-cell water and thermal management. However, it is increasingly become apparent that there is a need for more detailed lower lengthscale information to feed into the models due to microscale and mesoscale heterogeneities. In this talk, we will examine these issues with a focus on liquid-water movement in fuel-cell diffusion media and in water and ion transport in fuel-cell membranes including both proton and alkaline varieties. It is well known that continuum models use a volume-averaged approach to model liquid-water transport. This strategy is suitable for higher operating temperatures and homogeneous gas-diffusion-layer (GDL) morphologies, but, such structures are not realistic. To handle the complexity of the GDL morphology and access the expected capillary-fingering type of water transport in these porous media, pore-network models (PNMs) are utilized. However, while PNMs models capture the water transport through the GDL, they do not contain suitable descriptions of the other layers, complex nonlinear transport, and electrochemical phenomena. Here, we combine the advantage of both models in an iterative scheme integrating continuum and PN models to describe the multiphase and multiscale water transport properly. The coupling is achieved through an iterative scheme wherein the 2-D continuum PEFC model passes the calculated, heat and mass fluxes to the PNM, where they act as spatially varying source terms. Subsequently, the PNM returns to the continuum model a set of effective properties, such as thermal conductivity, effective diffusivity, and permeability, which are discretized along the electrode|GDL interface. This talk will discuss the work-flow between the coupled models including utilization of X-ray CT inputs and how such an approach can explain nonintuitive experimental data. For an ion-exchange membrane, mathematical modeling is ideally suited to explore the genesis of the observed water profiles and subsequently the mechanisms of water movement. Recently, such modeling has been receiving increased attention as new knowledge on the impact and control of the membrane/environment interface is elucidated. To model such effects requires the use of a multiscale framework involving mesoscale networks and microscale ion-transport information. The linking between these scales will be discussed including appropriate ways to incorporate molecular-level information into a physically consistent framework that still allows for easy incorporation into cell-level fuel-cell models. Acknowledgement I would like to acknowledge the various graduate students, postdocs, and collaborators who have worked on this research over the years. This work was supported by The Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

(Invited) A Complete Suite of Experimental Techniques for Electrical Characterization of Conventional and Incoming High-k Dielectric-Based Devices

High permittivity (high-k) dielectric films are of considerable interest as gate oxide materials in advanced complementary metal-oxide-semiconductor (CMOS) [1] as well as in dynamic and resistive random access memory devices (DRAM and ReRAM) [2]. While high-k materials can help to solve gate leakage problems with leading-edge processes, there still are some remaining challenges [3]. Drastic improvements in the quality of high-k films with respect to film density, thermal and electrical stability, quality of the interfaces with silicon substrate and/or metal gates, have been produced. However, there are several technical hurdles such as threshold voltage instabilities, carrier channel mobility degradation, and long-term device reliability. In fact, the performance of high-k film-based CMOS devices is strongly limited by the trapping and detrapping of charges in the pre-existing traps inside the high-k dielectrics [4]; also, reliability and variability are major concerns in the ReRAM development [5, 6]. During the last years, and nowadays, there has been an intense worldwide scientific and technological interest in the area of metal/oxide and oxide/semiconductor interfaces. Defects existing in these emerging materials play an important role in device operation, so their use in nano-semiconductor technology can be seriously endangered. Despite the great effort carried out in the last years, the nature and formation of these defects are not well known yet, so the study of defects is a primary concern to be able to apply techniques which can minimize them. Since electrically active defects are atomic configurations which give rise to electronic sates, developing an atomic-scale understanding of defects is mandatory. Another topic of great interest is the current mechanism observed on high-k materials. The correlation between conduction mechanisms, defect location, and preferential energy values provides very relevant information about the very nature of defects and how these defects could be removed or diminished. In this work we show the application of the standard techniques, as well as the new ones, which we have developed, for the electrical characterization of thin high-k layer-based metal-insulator-semiconductor (MIS) and metal-insulator-metal (MIM) structures. All of them constitute a complete suite of experimental techniques to carry out an in-depth study of conventional and incoming high-k based devices. In Fig. 1 a schematic of the electrical characterization of CMOS devices is shown. As an illustration, Figs. 2(a) and (b) show some results of electrical characterization of MIM structures for ReRAM devices. A whole discussion of the use of these techniques will be given during the conference. [1] D. Panda, and T.-Y. Tseng, Thin Solid Films 531, 1 (2013). [2] J. A. Kittl, K. Opsomer, M. Popovici, N. Menou, et al. Microel. Engin. 86, 1789 (2009). [3] J.-S. Jung, S.-K. Lee, C.-S. Hong, J.-H. Shin, J.-M. Kim, and J.-G. Kang, Thin Solid Films 589, 831 (2015). [4] S. Duenas, H. Castán, H. García, and L. Bailón, in Dielectric Materials, M. A. Silaghi, ed. InTech, ISBN: 978-953-51-0764-4, pp. 213-250 (2012). [5] J. Park, S. Jung, W. Lee, S. Kim, J. Shin, D. Lee, J. Woo, and H. Hwang, IEEE Electron Device Lett. 33, 646 (2012) [6] A. Fantini, L. Goux, R. Degraeve, D. J. Wouters, N. Raghavan, G. Kar, A. Belmonte, Y.Y. Chen, B. Govoreanu, and M. Jurczak, in Proc. IMW, pp. 30-33 (2013). Figure 1

Influence of mobile ions on the electroluminescence characteristics of methylammonium lead iodide perovskite diodes

Upon forward biasing the perovskite diodes, the turn-on voltage of the electroluminescence diminishes and its intensity substantially increases, suggesting that mobile ions do play an important role in device operation.

Memory Effects Based on Dopant Atoms in Nano-FETs

Transistors have been significantly downsized over the past decades, reaching channel dimensions of around 100 nm. In nanoscale, quantum effects start to play a key role in device operation, allowing the development of applications based on new physics. In silicon nanodevices, for instance, the device downsizing is associated with a reduction of the number of impurities (dopants) incorporated in the channel. Dopants can play an active role in device operation, mediating the electron transport between source and drain. Here, we present a new device concept of a memory based on the interaction between dopants in nanoscale field-effect transistors. As a basis for memory operation, we show experimental results of single-electron charging in individual dopants monitored by a single-electron current flowing through a dopant array.

Characteristics of a GaAs-InGaAs quantum-well resonant-tunneling switch

A switching device, with a p-type delta-doped sheet in the center of an InGaAs-GaAs quantum well, has been fabricated and demonstrated. An N-shaped negative-differential-resistance phenomenon resulting from the resonant-tunneling effect through the miniband is observed in the current-voltage measurement. From the experimental results, it is seen that the temperature plays an important role in device operation. The influences of temperature upon the peak-current voltage, valley-current voltage, peak-current density, and valley-current density are studied and discussed.