Chih-Jen Shih

The miniaturization of OLEDs is critical for next-generation ultrahigh-resolution displays and integrated photonics. However, traditional vacuum evaporation and inkjet printing methods are incompatible with the lithographic scaling processes that underpin silicon electronics, hindering true monolithic integration with CMOS circuits. Here, we present electroluminescent photoresists (ELPRs) synthesized via atom transfer radical polymerization (ATRP) that can be directly patterned by UV and electron beam lithography. These multi-arm star polymers feature a core-shell architecture designed to embed the TADF emitters within a protective host shell, segregating them from the reactive photocrosslinking moieties on the surface. We demonstrate robust processing orthogonality in sequential multilayer ELPR photolithography, enabling sub-diffraction fluorescence nanopatterns with critical dimensions down to 110 nm. We validate their device performance with full-color, UV-patterned OLEDs exhibiting external quantum efficiencies (EQEs) exceeding 13%.

The miniaturization of organic light-emitting diodes is critical for next-generation ultrahigh-resolution displays and integrated photonics ^1–8 . However, traditional vacuum evaporation and inkjet printing methods are incompatible with the lithographic scaling processes that underpin silicon electronics ^9–16 , hindering true monolithic integration with complementary metal–oxide–semiconductor circuits. Here we present electroluminescent photoresists synthesized via atom transfer radical polymerization that can be directly patterned by ultraviolet and electron-beam lithography. These multi-arm star polymers feature a core–shell architecture designed to embed the thermally activated delayed fluorescence emitters within a protective host shell, segregating them from the reactive photocrosslinking moieties on the surface. The site-specific isolation ensures that crosslinking reactions occur at the periphery, leaving the emissive cores intact and preserving high electroluminescence. We demonstrate robust processing orthogonality in sequential multilayer electroluminescent photoresist photolithography, enabling subdiffraction fluorescence nanopatterns with critical dimensions down to 110 nm. We validate their device performance with multicolour, ultraviolet-patterned organic light-emitting diodes exhibiting external quantum efficiencies exceeding 13%. These results not only pave the way for extending Moore’s law to organic optoelectronics but also unlock their potential for monolithic optoelectronic integration.

Flexible all‐perovskite tandem solar modules offer high power‐to‐weight ratios, making them promising for applications in flexible electronics and aerospace. However, their fabrication over large area remains challenging due to difficulties in achieving uniform coating and controlled crystallization of perovskites using scalable meniscus‐based deposition methods, partly arising from poor ink‐substrate adhesion. Herein, perovskite ink wettability is improved by utilizing nickel oxide (NiO _x ) interlayer to suppress the aggregation of self‐assembled molecules (SAMs) and enhance the hydrophilicity of the SAM layer. As a result, wide‐bandgap (WBG) perovskite films were deposited onto large‐area flexible substrates via doctor‐blade coating, exhibiting excellent spatial uniformity and achieving minor pixel‐to‐pixel variation in power‐conversion efficiencies (PCEs) on cell scale. The best‐performing flexible WBG perovskite solar cells and mini‐modules achieve PCEs of 16.7% and 13.3%, respectively. Furthermore, when integrated with a blade‐coated narrow‐bandgap perovskite subcell, this strategy enables the fabrication of flexible all‐perovskite tandem solar cell with a PCE of 23.3%. An efficiency exceeding 20% is also demonstrated for flexible all‐perovskite tandem mini‐modules over an aperture area of 10.8 cm ² . This study provides important insights into the regulation of SAM growth and establishes a foundation for the development of high‐efficiency flexible all‐perovskite tandem solar modules.

Vertical‐cavity surface‐emitting lasers (VCSELs) are vital for modern photonics, offering compactness, low thresholds, and ease of integration. Pushing them to wavelength‐scale dimensions, however, introduces fabrication and performance challenges, especially when using organic materials. Here, we demonstrate the miniaturization of organic polariton VCSELs based on the blue emitter molecule BSBCz. Using emitter:host evaporation through ultra‐thin shadow masks, we fabricate isolated microcavities with sizes down to 5 µm, the smallest dimensions reported so far for coevaporation micropatterning, and achieved optically‐pumped polariton lasing with record‐low thresholds down to 2.63 pJ (0.21 µJ/cm ² ), substantially lower than the 21.2 pJ (6.75 µJ/cm ² ) obtained for unpatterned reference devices. We further elucidate the influence of concentration of active material. Our lateral confinement approach paves the way for scalable, low‐threshold polariton lasers and may support the future development of monolithically integrated organic lasers driven by direct current injection.

This work presents a CMOS-only [micro-electromechanical systems (MEMS)-free] electronic nose (e-nose) for concurrent multi-gas-sensing applications. The proposed system integrates 4096 capacitance-to-digital converter (CDC) pixels, each implementing a compact bandpass sigma–delta ( $\Sigma \Delta $ ) ADC with a single feedback coefficient and no additional feedforward or feedback paths, achieving each pixel footprint of only $45\times 45~\mu $ m. The e-nose can achieve full baseline recovery and sensor reusability through an in-pixel heater to enable rapid and complete desorption of gas molecules from the sensing surface. The chip also includes 128 temperature-sensing pixels for on-chip thermal monitoring, utilizing a bandgap-based temperature sensor followed by a hybrid active–passive $\Sigma \Delta $ ADC, maintaining the same compact pixel footprint as the CDC pixels. The system operates from a 1.1-V supply with a power consumption of $10.3~\mu $ W per pixel at a 1-MHz sampling rate. To achieve high molecular selectivity, metal–organic framework (MOF) materials are utilized as the sensing interface. Two MOFs: CoNi–Pyz and HKUST-1 are employed for selective detection of ammonia (NH₃) and isopropyl alcohol (IPA), respectively, on the same chip. For NH₃ sensing, the proposed e-nose achieves a limit of detection (LoD) of 5 ppm, a sensitivity of 0.012 ( $\Delta $ C/C)/ppm, and a wide sensing range from 5 to 1000ppm. To the best of authors’ knowledge, this work achieves the highest reported density for a CMOS solid-state e-nose and represents the first demonstration of integrating both single and multiple MOF transducer materials directly on a CMOS chip. It also establishes a thermodynamically modulated sensing approach enabled by the in-pixel heater, ensuring full sensor reset and reusability.

The mechanism of thermally enhanced luminescence (TEL), such as thermally activated delayed fluorescence (TADF) and thermally stimulated delayed phosphorescence (TSDP), is of fundamental importance in the molecular design of emissive transition‐metal complexes, as it can enable bright emission with enhanced radiative rate for high‐performance organic light‐emitting diodes (OLEDs). It is essential to resolve the excited‐state landscape of complexes, including the correlation with their photophysical properties, to optimize the device efficiency. Here, we explore a series of Au(III) complexes containing asymmetric carbazolyl (Cz) motifs that regulate the co‐facial distance between the electron donor and acceptor moieties. Combining with the femtosecond transient absorption (fs‐TA) and in‐depth density functional theory computation, we reveal rapid reverse internal upconversion to a higher‐lying triplet state, T ₁ ’, which is thermally accessible from the lowest triplet state, T ₁ , at room temperature. The efficient spin‐flip process from T ₁ ’ to the lowest singlet state, S ₁ , and the ground state, S ₀ , leads to strong TEL through both TADF and TSDP pathways, substantially increasing the radiative rate to 10 ⁵ s ⁻¹ . The OLED devices based on the TEL Au(III) emitters reach external quantum efficiencies ( η _ext ) of 26.5% and 16.5% in doped and non‐doped devices, respectively. The doped OLED devices exhibited an η _ext roll‐off as low as 2% at a practical luminance of 1000 cd m ^{− 2} . We believe that the molecular design of highly efficient organometallic emitters of TEL character will be greatly facilitated by the mechanistic analysis and methodology presented here.

D -HLH-modulated crystallization improves quality and mitigates vertical heterogeneity in gas-quenched, blade-coated mixed Sn–Pb perovskites, enabling flexible all-perovskite tandem solar mini-modules with efficiencies above 20%.

Ultralight photovoltaics are indispensable wherever every gram counts, from self-powered Internet of Things nodes to free-hanging greenhouse covers. In dye-sensitized solar cells (DSCs) the required 450–500 °C sintering of the mesoporous TiO₂ (m-TiO₂) photoanode has so far limited the use of polymer substrates. Here, we replace the furnace step with flash infrared annealing. Near-IR radiation heats the 3.5 μm m-TiO₂ layer to 550 ± 20 °C while keeping a 12.5 μm indium-tin-oxide/polyimide foil below 170 °C with a water-cooled heat-sink. We obtain complete removal of organic binders, while the substrate sheet resistance increases modestly from 60.2 to 129.8 Ω sq^–1. Flexible DSCs reach power conversion efficiencies of 5.10% under AM 1.5G illumination, a record value for DSCs on sub-25 μm plastics. The finished devices deliver 51× the specific power of equivalent glass devices. A cradle-to-gate life cycle assessment normalized to power-per-mass reveals order-of-magnitude reductions in several categories compared with rigid hot-plate processing. Localized IR sintering thus removes the last processing barrier for truly roll-to-roll printable hybrid solar cells.

Flexible all-perovskite tandem solar cells (TSCs) promise lightweight power for portable and aerospace uses, yet performance remains limited by interfacial losses in narrow-bandgap (NBG) sub-cells, particularly arising from poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). Here, we uncover a previously unrecognized vertical phase segregation in PEDOT:PSS films, with an insulating PSS-rich surface layer atop a conductive PEDOT-rich base. This architecture induces interfacial electric dipoles that hinder efficient hole extraction. We find that the inclusion of Triton X-100 disrupts this segregation by modulating polymer interactions, thereby suppressing surface dipole formation. NBG perovskite cells incorporating this modified interface exhibit enhanced performance and reproducibility. This strategy enables flexible TSCs with a power conversion efficiency (PCE) of 25.4% and a proof-of-concept flexible tandem solar mini-module reaches 19.7%, with theoretical modeling projecting module efficiencies exceeding 24%. These results provide key insights into PEDOT:PSS interfacial phenomena and elucidate design principles for optimizing interfaces for next-generation flexible perovskite tandems.

Miniaturization of light-emitting diodes below the diffraction limit of the emission wavelength can enable super-resolution imaging and on-chip light sources for ultrabroadband chiplet communication. Organic light-emitting diodes, although suitable for miniaturization due to their emission from localized excitons, suffer from the limited compatibility of organic materials with traditional photolithographic patterning. Here we develop a method for the scalable fabrication of nanoscale organic light-emitting diodes with pixel densities up to 100,000 pixels per inch, periodicity of 250 nm and the smallest pixel size in the order of 100 nm. We realize the direct nanoscale patterning of organic semiconductors by self-aligned nanostencil etching and lithography. The process is resist-free and involves etching and evaporation through nanoapertures in a free-standing film adhering to the substrate. A nanoscale organic light-emitting diode surface with over 1 megapixel exhibits an average external quantum efficiency of 13.1%. We also demonstrate electroluminescent metasurfaces with subwavelength-scale meta-atoms that can electrically modulate the emitted light. The diffractive coupling between nanopixels enables control over the far-field emission properties of light, including directionality and polarization. These results pave the way for hybrid integrated photonics technologies, including visible-light communication, lasing and high-resolution displays.