Thermophotovoltaic approaches that take advantage of near-field evanescent modes are being actively explored due to their potential for high-power density and high-efficiency energy conversion. However, progress towards functional near-field thermophotovoltaic devices has been limited by challenges in creating thermally robust planar emitters and photovoltaic cells designed for near-field thermal radiation. Here, we demonstrate record power densities of ~5 kW/m² at an efficiency of 6.8%, where the efficiency of the system is defined as the ratio of the electrical power output of the PV cell to the radiative heat transfer from the emitter to the PV cell. This was accomplished by developing novel emitter devices that can sustain temperatures as high as 1270 K and positioning them into the near-field (<100 nm) of custom-fabricated InGaAs-based thin film photovoltaic cells. In addition to demonstrating efficient heat-to-electricity conversion at high power density, we report the performance of thermophotovoltaic devices across a range of emitter temperatures (~800 K–1270 K) and gap sizes (70 nm–7 µm). The methods and insights achieved in this work represent a critical step towards understanding the fundamental principles of harvesting thermal energy in the near-field.

This review comprehensively addresses the developments and applications of polymer materials in optoelectronics. Especially, this review introduces how the materials absorb, emit, and transfer charges, including the exciton–vibrational coupling, nonradiative and radiative processes, Förster Resonance Energy Transfer (FRET), and energy dynamics. Furthermore, it outlines charge trapping and recombination in the materials and draws the corresponding practical implications. The following section focuses on the practical application of organic materials in optoelectronics devices and highlights the detailed structure, operational principle, and performance metrics of organic photovoltaic cells (OPVs), organic light-emitting diodes (OLEDs), organic photodetectors, and organic transistors in detail. Finally, this study underscores the transformative impact of organic materials on the evolution of optoelectronics, providing a comprehensive understanding of their properties, mechanisms, and diverse applications that contribute to advancing innovative technologies in the field.

Control of heat flow is critical for thermal logic devices and thermal management and has been explored theoretically. However, experimental progress on active control of heat flow has been limited. Here, we describe a nanoscale radiative thermal transistor that comprises of a hot source and a cold drain (both are ~250 nm-thick silicon nitride membranes), which are analogous to the source and drain electrodes of a transistor. The source and drain are in close proximity to a vanadium oxide (VO_x)-based planar gate electrode, whose dielectric properties can be adjusted by changing its temperature. We demonstrate that when the gate is located close ( < ~1 µm) to the source-drain device and undergoes a metal-insulator transition, the radiative heat transfer between the source and drain can be changed by a factor of three. More importantly, our nanomembrane-based thermal transistor features fast switching times ( ~ 500 ms as opposed to minutes for past three-terminal thermal transistors) due to its small thermal mass. Our experiments are supported by detailed calculations that highlight the mechanism of thermal modulation. We anticipate that the advances reported here will open new opportunities for designing thermal circuits or thermal logic devices for advanced thermal management.

Designing an efficient and stable hole transport layer (HTL) material is one of the essential ways to improve the performance of organic–inorganic perovskite solar cells (PSCs). Herein, for the first time, an efficient model of a hole transport material (HTM) is demonstrated by optimized doping of a conjugated polymer TFB (poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)diphenylamine)]) with a non-hygroscopic p-type dopant F4-TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) for high-efficiency PSCs. The PSC with the F4-TCNQ doped TFB exhibits the best power conversion efficiency (PCE) of 17.46%, which surpasses that of the reference devices, i.e., 16.64 (LiTFSI + TBP-doped Spiro-OMeTAD as the HTM) and 11.01% (LiTFSI + TBP-doped TFB as the HTM). F4-TCNQ doped TFB was believed to favor efficient charge and energy transfer between the perovskite and the hole transport layer and to reduce charge recombination as evidenced by steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) analysis. Moreover, the hydrophobic nature of F4-TCNQ contributed to enhancing the stability of the device under ambient conditions with a RH of 45%. The device reported herein retained ca. 80% of its initial efficiency after 10 days, significantly superior to both LiTFSI + TBP-doped Spiro-OMeTAD (ca. 30%) and LiTFSI + TBP-doped TFB (ca. 10%) based counterparts. This simple yet novel strategy paves the way for demonstrating a promising route for a wide range of highly efficient solar cells and other photovoltaic applications.

An efficient hole-transporting layer (HTL) based on functionalized two-dimensional (2D) MoS₂-poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composites has been developed for use in organic solar cells (OSCs). Few-layer, oleylamine-functionalized MoS₂ (FMoS₂) nanosheets were prepared via a simple and cost-effective solution-phase exfoliation method; then, they were blended into PEDOT:PSS, a conducting conjugated polymer, and the resulting hybrid film (PEDOT:PSS/FMoS₂) was tested as an HTL for poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PCBM) OSCs. The devices using this hybrid film HTL showed power conversion efficiencies up to 3.74%, which is 15.08% higher than that of the reference ones having PEDOT:PSS as HTL. Atomic force microscopy and contact angle measurements confirmed the compatibility of the PEDOT:PSS/FMoS₂ surface for active layer deposition on it. The electrical impedance spectroscopy analysis revealed that their use minimized the charge-transfer resistance of the OSCs, consequently improving their performance compared with the reference cells. Thus, the proposed fabrication of such HTLs incorporating 2D nanomaterials could be further expanded as a universal protocol for various high-performance optoelectronic devices.