Solar infrared radiation towards building energy efficiency: measurement, data, and modeling

With the recent discoveries and engineering solutions emerging in nanomaterials and nanostructures, independent band modulation of solar radiation on building envelopes, including glazing systems, has become increasingly viable as a potential means of improving building energy savings and indoor visual comfort. However, when it comes to the prediction of these new materials’ potential energy performance in buildings, most studies utilize a simple solar irradiance (e.g., global horizontal solar irradiance, direct beam solar irradiance) or a rough estimation of solar infrared (e.g., 50% solar irradiance) as input, which may cause significant errors. Consequently, there is a pressing need for reliable performance estimations of the solar infrared control and response at the building’s scale. To assess this, we need a solar spectral irradiance model, or at least a wideband (visible or infrared) solar irradiance model, as input. To develop this new type of model, one needs to understand the modeling-related key elements, including available solar spectral irradiance datasets, data collection methods, and modeling techniques. As such, this paper reviews the current major measurement methods and tools used in collecting solar spectral irradiance data with a focus on the solar infrared region, identifies the available related resources and datasets that particularly encompass the solar spectral irradiance data with a sufficient wavelength range, and studies existing solar irradiation modeling techniques for building simulations. These investigations will then form the background and backbone for a study scheme of solar infrared radiation modeling and indicate future research paths and opportunities.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Experimental study on microstructure and heating characteristics of water-soaked and air-dried bituminous coal

In order to study the microstructure and heating characteristics of water-soaked air-dried bituminous coal, the bituminous coal samples from a coal mine in Shaanxi Province were selected. Using low temperature liquid nitrogen adsorption instrument and thermogravimetric analyzer, the specific surface area, pore volume and thermogravimetric and derivative thermogravimetric tests were carried out on the coal samples soaked for 30 days, 60 days and 90 days and raw coal samples after constant temperature drying at 25 ℃ for 72 h. The influence mechanism of long-term soaking and air-drying on the physical characteristics and activation energy of bituminous coal during heating process was explored. The results show that the specific surface area and total pore volume of coal samples change with the increase of soaking time. After soaking for 90 days and drying, the contribution proportion of micropore contrast surface area and total pore volume was the largest, and the contribution proportion was larger than that of other pore sizes. It is speculated that the coal sample soaked in water for 90 days after drying, the faster the coal oxygen reaction rate, the higher the coal spontaneous combustion tendency. In the process of heating up, the characteristic temperature difference and characteristic temperature point change of coal samples at different soaking time are different

Hybrid System Combining Two-Dimensional Materials and Ferroelectrics and Its Application in Photodetection

Photodetectors are one of the most important components for a future "Internet-of-Things" information society. Compared to the mainstream semiconductor-based photodetectors, emerging devices based on two-dimensional (2D) materials and ferroelectrics as well as their hybrid systems have been extensively studied in recent decades due to their outstanding performances and related interesting physical, electrical, and optoelectronic phenomena. In this paper, we review the photodetection based on 2D materials and ferroelectric hybrid systems. The fundamentals of 2D and ferroelectric materials as well as the interaction in the hybrid system will be introduced. Ferroelectricity modulated optoelectronic properties in the hybrid system will be discussed in detail. After the basics and figures of merit of photodetectors are summarized, the 2D-ferroelectrics devices with different structures including p-n diodes, Schottky diodes, and field-effect transistors will be reviewed and compared. The polarization of ferroelectrics offers the possibility of the modulation and enhancement of the photodetection in the hybrid detectors, which will be discussed in depth. Finally, the challenges and perspectives of the photodetectors based on 2D ferroelectrics will be proposed. This Review outlines the important aspects of the recent development of the hybrid system of 2D and ferroelectric materials, which could interact with each other and thus lead to photodetectors with higher performances. Such a Review will be helpful for the research of emerging physical phenomena and for the design of multifunctional nanoscale electronic and optoelectronic devices

Multiwavelength High-Detectivity MoS2 Photodetectors with Schottky Contacts

Photodetection is one of the vital functions for the multifunctional "More than Moore" (MtM) microchips urgently required by Internet of Things (IoT) and artificial intelligence (AI) applications. The further improvement of the performance of photodetectors faces various challenges, including materials, fabrication processes, and device structures. We demonstrate in this work MoS2 photodetectors with a nanoscale channel length and a back-gate device structure. With the mechanically exfoliated six-monolayer-thick MoS2, a Schottky contact between source/drain electrodes and MoS2, a high responsivity of 4.1 × 103 A W-1, and a detectivity of 1.34 × 1013 cm Hz1/2 W-1 at 650 nm were achieved. The devices are also sensitive to multiwavelength lights, including 520 and 405 nm. The electrical and optoelectronic properties of the MoS2 photodetectors were studied in depth, and the working mechanism of the devices was analyzed. The photoinduced Schottky barrier lowering (PIBL) was found to be important for the high performance of the phototransistor

Ambipolar MoS2 Field Effect Transistors with Negative Photoconductivity and High Responsivity Using an Ultrathin Epitaxial Ferroelectric Gate

Abstract: Ferroelectric field effect transistors (FeFETs), characterized by their low power consumption and polarization effect, can be employed in photodetectors based on 2D materials. In this paper, a MoS2 phototransistor with epitaxial ferroelectric (Hf0.5Zr0.5)O2 (HZO) is reported as a gate dielectric layer. Gate‐dielectric‐polarization‐dependent ambipolar behavior is observed in the FET, and relatively low power consumption and hysteresis‐free loop are achieved in the FeFET. The anomalous negative photoconductivity (NPC) is observed as well. Possible reasons for such phenomenon are clarified including the photogating effect originating from the interface traps and the polarization‐dependent electric‐field control through ferroelectric gating. The high responsivity of −8.44 × 103 A W−1 in the negative photoconductivity as well as the response time of 500 ms are reported. The demonstrated Molybdenum disulfide (MoS2) FeFET photodetectors show great potential in the on‐chip complementary metal‐oxide semiconductor (CMOS)‐compatible circuits for multifunctional devices

Impact of the channel length on molybdenum disulfide field effect transistors with hafnia-based high- k dielectric gate

International audienceField effect transistors (FETs) using two-dimensional molybdenum disulfide (MoS 2) as the channel material has been considered one of the most potential candidates for future complementary metal-oxide-semiconductor technology with low power consumption. However, the understanding of the correlation between the device performance and material properties, particularly for devices with scaling-down channel lengths, is still insufficient. We report in this paper back-gate FETs with chemical-vapor-deposition grown and transferred MoS 2 and Zr doped HfO 2 ((Hf,Zr)O 2 , HZO) high-k dielectric gates with channel lengths ranging from 10 to 30 μm with a step of 5 μm. It has been demonstrated that channels with the length to width ratio of 0.2 lead to the most superior performance of the FETs. The MoS 2 /HZO hybrid FETs show a stable threshold voltage of ∼1.5 V, current on/off ratio of >10 4 , and field effect mobility in excess of 0.38 cm 2 V −1 s −1. The impact of the channel lengths on FET performance is analyzed and discussed in depth. A hysteresis loop has been observed in the I ds − Vgs characteristics of the hybrid FETs, which has been further studied and attributed to the charge effect at the interfaces. The HZO films show a relatively weak ferroelectric orthorhombic phase and thus serve mainly as the high-k dielectric gate. Charge trapping in the HZO layer that might induce hysteresis has been discussed. Our results show that MoS 2 /HZO hybrid FETs possess great potential in future low power and high-speed integrated circuits, and future work will focus on further improvement of the transistor performances using ferroelectric HZO films and the study of devices with even shorter MoS 2 channels

Impact of the channel length on molybdenum disulfide field effect transistors with hafnia-based high-k dielectric gate

Field effect transistors (FETs) using two-dimensional molybdenum disulfide (MoS2) as the channel material has been considered one of the most potential candidates for future complementary metal-oxide-semiconductor technology with low power consumption. However, the understanding of the correlation between the device performance and material properties, particularly for devices with scaling-down channel lengths, is still insufficient. We report in this paper back-gate FETs with chemical-vapor-deposition grown and transferred MoS2 and Zr doped HfO2 ((Hf,Zr)O2, HZO) high-k dielectric gates with channel lengths ranging from 10 to 30 µm with a step of 5 µm. It has been demonstrated that channels with the length to width ratio of 0.2 lead to the most superior performance of the FETs. The MoS2/HZO hybrid FETs show a stable threshold voltage of ∼1.5 V, current on/off ratio of >104, and field effect mobility in excess of 0.38 cm2 V−1 s−1. The impact of the channel lengths on FET performance is analyzed and discussed in depth. A hysteresis loop has been observed in the Ids − Vgs characteristics of the hybrid FETs, which has been further studied and attributed to the charge effect at the interfaces. The HZO films show a relatively weak ferroelectric orthorhombic phase and thus serve mainly as the high-k dielectric gate. Charge trapping in the HZO layer that might induce hysteresis has been discussed. Our results show that MoS2/HZO hybrid FETs possess great potential in future low power and high-speed integrated circuits, and future work will focus on further improvement of the transistor performances using ferroelectric HZO films and the study of devices with even shorter MoS2 channels

Highly heterogeneous epitaxy of flexoelectric BaTiO3-δ membrane on Ge

The integration of complex oxides with a wide spectrum of functionalities on Si, Ge and flexible substrates is highly demanded for functional devices in information technology. We demonstrate the remote epitaxy of BaTiO3 (BTO) on Ge using a graphene intermediate layer, which forms a prototype of highly heterogeneous epitaxial systems. The Ge surface orientation dictates the outcome of remote epitaxy. Single crystalline epitaxial BTO3-δ films were grown on graphene/Ge (011), whereas graphene/Ge (001) led to textured films. The graphene plays an important role in surface passivation. The remote epitaxial deposition of BTO3-δ follows the Volmer-Weber growth mode, with the strain being partially relaxed at the very beginning of the growth. Such BTO3-δ films can be easily exfoliated and transferred to arbitrary substrates like Si and flexible polyimide. The transferred BTO3-δ films possess enhanced flexoelectric properties with a gauge factor of as high as 1127. These results not only expand the understanding of heteroepitaxy, but also open a pathway for the applications of devices based on complex oxides