Exciton-polaritons provide a great platform for developing ultrafast all-optical logic gates for quantum and optical chips. However, progress toward practical polariton logic remains limited due to incomplete logical functionality on a single device. Herein, we present a single-device perovskite polariton platform enabling reconfigurable, ultrafast logic gates with functional completeness. The device consists of an optically trapped perovskite microwire, generating well-controlled non-equilibrium polariton condensation states for multiple logic operation channels. By tailoring the power of signal and gate beams, the same device is programmed to execute three basic Boolean functions (AND,OR,and NOT) and a high-order XOR function with a high on/off ratio of 21 dB, and a fast response time 6.7 ps. The reconfigurability arises from the selective activation of different nonlinear responses of polariton condensates, including amplification, seeding state transitions, and nonlinear interaction. These results provide valuable insights for advancing exciton-polariton logic gates.

Flat-band bound states in the continuum (BICs) are topological states with suppressed group velocity and robustness against radiation loss, offering a powerful platform for the exploration of non-Hermitian, nonlinear, topological phenomena and device applications. Van der Waals (vdW) metasurfaces have recently emerged as promising candidates for sustaining BICs and hybridizing with material transitions. However, the realization of flat-band BICs remains elusive. Here, we experimentally demonstrate high-order polaritonic BICs on a wide-angle flat band utilizing a subwavelength (~$${\lambda }_{0}$$ /35) metasurface based on a vdW magnet CrSBr. The large oscillator strength of direct excitons in CrSBr enables near-ultrastrong coupling with the photonic BIC-band, leading to a polaritonic band with strongly suppressed angular dispersions. Remarkably, the second-order polaritonic BIC-band becomes flattened, with a vanishing energy variation over a wide angular range. In addition, we find that these polaritonic BIC-bands vanish in the transverse magnetic configuration, while leading to hyperbolic exciton-polaritons within the Reststrahlen band. Our findings underscore CrSBr as an exceptional platform for exploring flat-band photonics and polaritonics, paving a new avenue for advances in next-generation optical and quantum technologies. Flat-band bound states in the continuum are localized optical modes with near-zero group velocity, and in their idealized form, infinite Q-factors. Realization of such states is challenging, but here, Shen and coauthors demonstrate polaritonic bound states in the continuum in a metasurface based on the van der Waals magnet, CrSBr.

Hyperbolic and quasi-flat isofrequency contours (IFCs) are used for beam canalization and can be created by tilted Dirac points in photonic systems. Dirac points in microcavities are generated by the combination of transverse-electric/transverse-magnetic splitting and linear birefringence. We show that the canalization is here strongly assisted by the coupling between the spatial dynamics and polarization pseudospin precession. This dynamics is well described analytically and numerically as the action of a non-Abelian gauge field on emergent charges (spin current). We demonstrate a ten-fold enhancement of the canalization for a Gaussian beam by the gauge field, as compared to a description based solely on the group velocity associated with the IFCs.

Non-Hermitian physics has recently transformed our understanding of topology by uncovering a range of effects that are unique to systems with gain and loss. The realization of non-Hermitian topology in strongly coupled light-matter systems not only offers degrees of freedom for the enhanced manipulation of topological phenomena, but is also promising for developing on-chip active photonic devices. Exciton-polaritons-strongly coupled quasiparticles from excitons and photons-emerge as a promising candidate with intrinsic non-Hermitian features. However, limited by the challenges in achieving non-reciprocity, the experimental observation of non-Hermitian topology and its associated transport features has remained elusive. Here we experimentally demonstrate the non-Hermitian topology of exciton-polaritons induced by a twist degree of freedom in a liquid-crystal-filled CsPbBr3 perovskite microcavity at room temperature. The geometric twist between birefringent perovskites and liquid crystals acts as a degree of freedom to tailor the polaritonic complex spectra, leading to non-Hermitian bands with spectral winding topology and non-reciprocity. Furthermore, the induced non-Hermitian topology gives rise to the non-Hermitian exciton-polariton skin effect in real space, manifesting as polariton accumulation at open boundaries. Our findings open new perspectives on tunable non-Hermitian phenomena and the development of on-chip polaritonic devices with enhanced functionalities.

The ability to steer polariton flow on-demand holds significant promise towards nanophotonic applications and photonic circuitry. Polariton canalization, exhibiting intrinsic collimation and diffractionless transport, emerges as a promising solution without guiding structures. However, earlier demonstrations have been restricted to certain crystal surfaces with intrinsic hyperbolic responses and operated in the linear regime. Here, we experimentally demonstrate canalization of nonlinear exciton polariton condensates with optical reconfigurability in a birefringent CsPbBr3 perovskite crystal without intrinsic hyperbolic response. By embedding the birefringent perovskite crystal into a planar microcavity, the interplay between cavity transverse-electric-transverse-magnetic splitting and crystalline birefringence produces an anisotropic band geometry with a hyperbolic-flat-parabolic evolution of polaritonic isofrequency contours (IFCs). Nonresonant pumping drives exciton polariton condensation onto flat far-field contours with nonlinear emission amplification, leading to coherent canalized flows with over twentyfold collimation with respect to arc-shaped contours. Reconfiguring the optical pumping-spot size allows switching the nonlinear polariton condensates into hyperbolic and parabolic IFC regimes, leading to divergent propagation behaviour with collimating reconfiguration. Our study reveals a distinct canalization framework for shaping the nonlinear exciton-polariton condensate flows, opening opportunities for all-optical polaritonic logic circuits based on stabilized nonlinear quantum interconnects.

Topological active materials have emerged as a powerful paradigm bridging the discovery of exotic topological phases of matter with the development of functional topological devices. The recent extension of these material systems into dynamic regime, where topological properties can be actively manipulated at ultrafast timescales, promises unprecedented control over topological states and their functionalities. However, translating the static topological lasing signals into high-performance logic functions remain highly challenging, which imposes a far more stringent set of materials attributes. Here, leveraging the strong nonlinearity and pronounced spectral isolation of perovskite exciton-polaritons embedded in a Dirac vortex microcavity, we experimentally demonstrate the dynamic topological Majorana-like state polariton condensation with its ultrafast logic operations at room temperature, achieving record extinction ratio (∼20 dB), extremely low control fluence (∼0.2 nJ/cm 2 ) and sub-picosecond response time (∼500 fs). Our results expand the frontier of dynamic topology and establish an innovative pathway towards robust, ultrafast, and reconfigurable on-chip polaritonic logic circuits.

Exciton-polaritons (EPs) are hybrid light-matter quasi-particles that hold great potential for quantum optics and optoelectronics. Bulk EPs, or elementary dressed states, are limited by the small exciton binding energies and oscillator strengths of existing semiconductors, thus restricting their formation to cryogenic temperatures and hindering practical applications. Here we overcome this fundamental constraint and achieve room-temperature control over bulk EPs in a bare halide perovskite crystal featuring an unusual exciton-photon-phonon coupling. Time-of-flight measurements and first-principles calculations reveal an exceptionally large exciton longitudinal-transverse splitting up to similar to 50 meV that substantially modifies the EP dispersion. From the coherent EP dynamics, we establish that the long-range bulk EP propagation occurs in the ballistic regime. We further demonstrate tailorable slow light with different halide perovskite crystals, with a broad spectral window extending across the visible range. Importantly, our findings reveal the intrinsic polaritonic properties of layered halide perovskite semiconductors, paving the way for their straightforward application as optical delay generators and ultrafast photonic devices.

Halide perovskites have emerged as a compelling material for a broad range of optoelectronic applications, including light-emitting diodes, phototransistors, light-sensing and imaging systems. To enable practical application and compatibility with existing consumer electronics, they must be integrated with heterogeneous electronic platforms, such as complementary metal-oxide-semiconductor chips or thin-film transistors. Such integration is pivotal for transitioning perovskite technologies from laboratory demonstrations to commercial applications. In this perspective, we summarize recent progress in the system-level integration of perovskite optoelectronics with driving backplanes, compare key performance metrics with industrial benchmarks, discuss major challenges, and outline future directions and application prospects for perovskite optoelectronics.

Coupling between quantum or classical degrees of freedom underpins a wide range of physical phenomena, from condensed matter systems to engineered photonic lattices. While positive coupling arising naturally from evanescent interactions has been extensively studied and employed, negative coupling unlocks unique phenomena that are challenging to realize with positive coupling alone. Exciton-polariton micropillars, celebrated for enabling topological lasers, reservoir computing, and quantum simulations, have primarily relied on positive coupling. In this work, we experimentally demonstrate negative coupling between two micropillars using an additional larger micropillar. By combining positively and negatively coupled micropillars, we construct a Su-Schrieffer-Heeger (SSH) topological lattice with a significant topological gap of approximately 15 meV, where band inversion occurs at the center of the Brillouin zone (BZ), rather than at the edges as in conventional SSH lattices. Under non-resonant excitation, we achieve polariton condensation in the in-gap topological edge states at room temperature. Our study introduces a universal method to realize negative coupling in polariton systems, paving the way for novel polaritonic devices based on lattices with arbitrarily controlled coupling signs. Negative coupling is an intriguing mechanism for linking lattice sites, enabling phenomena unattainable with positive coupling alone. Here, the authors introduce this unique coupling into the polariton system and demonstrate topological polariton condensation in lattices with negative coupling.

Spintronics, whereby electron spin is harnessed for carrying and processing information, could play an important role in the future of information technology. However, despite ongoing research efforts, establishing a materials platform that suits spin-optronics, particularly one that operates effectively at ambient temperatures, continues to represent a challenge. Recent advancements in transition metal dichalcogenides are opening up new opportunities, with exciton-polaritons in these materials being promising for the development of spintronic customizable devices that function at ambient temperatures. Although transition metal dichalcogenide polaritons have shown promising potential, spin-anisotropic nonlinearities have been missing. Here we demonstrate the absence of spin-anisotropic interaction in a monolayer WS2 microcavity at room temperature and show how spin anisotropy can be recovered by engineering double WS2 layer structures with varied interlayer spacing. We attribute this phenomenon to a distinctive feature in exciton-polariton physics: layer-dependent polariton-phonon coupling. We use theoretical calculations of the phonon electrostatic potentials finding a drastically different coupling strength for single and double monolayer samples and discuss qualitatively how this explains the observed spin-anisotropic response. This is further consistent with experiments on multi-WS2 layer samples and the identification of a critical separation distance, above which an effective single monolayer spin-anisotropic response is recovered, both in experiment and theory. Our work lays the groundwork for the development of spin-optronic polaritonic devices at room temperature.

The formation and dynamics of bipolarons are crucial in determining the electrical properties of molecularly doped conjugated polymers. Traditionally, bipolarons are known to form at very high doping levels through the combination of two adjacent polarons, a process that is generally accompanied by structural disorder and impaired carrier transport. Here, it is demonstrated that bipolaron formation can occur at both the early stage with low doping levels and the late stage with high doping levels in 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) dip-doped conjugated polymer films with glycol sidechains. Bipolaron formation at the early stage is discovered to be mainly associated with double doping, which is uncommon in conventional doped polymer systems. In contrast, bipolaron formation at the late stage is dominated by combining two polarons. Furthermore, these bipolarons are observed to behave differently: early-stage bipolarons generated through double doping enhance both the molecular ordering and carrier transport, whereas late-stage bipolarons resulting from polaron combination occur alongside detrimental effects in structural and transport properties. These findings provide new insights into the mechanisms of bipolaron formation across different doping levels and underscore the potential for optimizing doping strategies. A deeper understanding of bipolarons can guide the design of next-generation molecularly doped conjugated polymers with improved performance.

Monolithic perovskite-organic tandem solar cells (POTSCs) have attracted considerable attention in recent years due to their compatible fabrication routes and advances in single-cell efficiencies. To further boost the performance of POTSCs, reducing the voltage losses that mainly arise from wide bandgap (WBG, >1.7 eV) perovskite subcells and interconnecting layers (ICLs) is critical. Here, a new ICL with a configuration of C-60/YbOx/Au/MoOx is demonstrated for constructing the monolithic POTSC. The YbOx-based ICL benefits from an ohmic contact and high transparency, resulting in improved POSTC performance. The champion device presents a PCE of 23.2% owing to a high V-OC of 2.11 V (approximately equal to the sum of individual V-OC's of the subcells) without compromising the short-circuit current density and fill factors. This work opens an avenue for developing efficient ICLs in POTSCs.

Halide perovskites offer a great platform for room-temperature exciton-polaritons (EPs) due to their strong oscillator strength and large exciton binding energy, promising applications in next-generation photonic and polaritonic devices. Efficient manipulation of EP transport and relaxation is critical for device performance, yet their spatiotemporal dynamics across different in-plane momenta (k//) remain poorly understood due to limitations in experimental access. In this work, we employ energy-resolved transient reflectance microscopy (TRM) combined with the dispersion relation of EPs to achieve high-resolution imaging of EP transport at specific k//. This approach directly reveals the quasi-ballistic transport and ultrafast relaxation of EPs in different k// regions, showcasing diffusion as fast as 490 cm2/s and a relaxation time of 95.1 fs. Furthermore, by tuning the detuning parameter, we manipulate the ballistic transport group velocity and relaxation time of EPs across varying k//. Our results reveal key insights into the dynamics of EP transport and relaxation, providing valuable guidance for the design and optimization of polaritonic devices.

When disassembled into monolayers from their bulk crystals, two-dimensional (2D) transition metal dichalcogenides (TMDCs) exhibit exotic optical properties dominated by strong excitonic effects. Reassembling 2D TMDC layers to build bulk excitonic crystals can significantly boost their optical performance and introduce emerging functionalities toward optoelectronic and valleytronic applications. However, maintaining or manipulating 2D excitonic properties in bulk structures or superlattices is challenging. Herein, we developed a method to precisely construct m∙2N-layer artificial excitonic crystals with only a number N of stacking operations (m denotes the layer number of the initial material unit), referred to as the "2^N method". We successfully fabricated a millimeter-scale weakly coupled 16-layer MoS2 single crystal with zero interlayer twist angle, which retains monolayer-like exciton properties and exhibits remarkable enhancements up to 643% and 646% in their absorption and photoluminescence (PL) features, respectively. Moreover, we created a WSe2/(MoS2/WSe2)3/MoS2 superlattice starting from monolayer WSe2 and MoS2, which demonstrated an intensity increase of up to 400% in quadrupolar interlayer exciton (IX) emission as compared to dipolar IXs in its bilayer counterpart. Our work shows a promising approach for the design and bottom-up fabrication of excitonic crystals, promoting the exploration of excitonic physics in complex van der Waals (vdW) structures and their applications in optoelectronic devices.

Self‐assembled monolayers (SAMs) play a crucial role in high‐performance perovskite solar cells (PSCs). However, the incompatibility between the nonpolar head groups of SAMs and the polar perovskite precursor solutions leads to SAM assembly defects and wettability issues, consequently impacting device efficiency. Moreover, the uneven distribution of hydroxyl groups on the surface of conventional transparent conductive oxide substrates is detrimental to SAMs onto them. Here, a dual‐sided passivation strategy is reported based on a co‐adsorbed approach, in which (4‐(3,6‐dimethyl‐9H‐carbazole‐9‐yl)butyl)phosphonic acid (Me‐4PACz) is doped with phaclofen (PLF) self‐assembly on the NiO x substrate. By compensating for the unanchored sites of Me‐4PACz, the phosphonic acid groups in PLF adsorb onto the NiO x surface, enabling more uniform and ordered anchoring of SAMs as well as improved wettability for perovskite deposition. This leads to optimized surface morphology and enhanced interface contact. Additionally, the amino groups in PLF passivate the defects at the buried perovskite interface, suppressing non‐radiative recombination during charge transport. The champion PSC fabricated using this co‐adsorbed strategy achieves a high fill factor of 84.92%, a power conversion efficiency of 24.04%, and excellent long‐term stability under ISOS‐D‐1I and ISOS‐T‐1I protocols, maintaining over 85% of the initial efficiency after >1000 h under thermal cycling conditions.

Obtaining micron-thick perovskite films of high quality is key to realizing efficient and stable positive (p)-intrinsic (i)-negative (n) perovskite solar cells1,2, but it remains a challenge. Here we report an effective method for producing high-quality, micron-thick formamidinium-based perovskite films by forming coherent grain boundaries, in which high-Miller-index-oriented grains grow on the low-Miller-index-oriented grains in a stabilized atmosphere. The resulting micron-thick perovskite films, with enhanced grain boundaries and grains, showed stable material properties and outstanding optoelectronic performances. The small-area solar cells achieved efficiencies of 26.1%. The 1-cm2 devices and 5 cm × 5 cm mini-modules delivered efficiencies of 24.3% and 21.4%, respectively. The devices processed in a stabilized atmosphere presented a high reproducibility across all four seasons. The encapsulated devices exhibited superior long-term stability under both light and thermal stressors in ambient air.

Transition-metal dichalcogenide monolayers possess large exciton binding energy and a robust valley degree of freedom, making them a viable platform for the development of spintronic devices capable of operating at room temperature. The development of such monolayer TMD-based spintronic devices requires strong spin-dependent interactions and effective spin transport. This can be achieved by employing exciton-polaritons. These hybrid light-matter states arising from the strong coupling of excitons and photons allow high-speed in-plane propagation and strong nonlinear interactions. Here, we demonstrate the operation of all-optical polariton spin switches by incorporating a WS2 superlattice into a planar microcavity. We demonstrate spin-anisotropic polariton nonlinear interactions in a WS2 superlattice at room temperature. As a proof-of-concept, we utilize these spin-dependent interactions to implement different spin switch geometries at ambient conditions, which show intrinsic sub-picosecond switching time and small footprint. Our findings offer new perspectives on manipulations of the polarization state in polaritonic systems and highlight the potential of atomically thin semiconductors for the development of next generation information processing devices. Exciton-polaritons result from the strong coupling of excitons and photons, exhibiting strong nonlinearity. Here, Zhao et al demonstrate room-temperature optical polariton spin-switching in a tungsten disulfide superlattice.

Topological exciton-polaritons are a burgeoning class of topological photonic systems distinguished by their hybrid nature as part-light, part-matter quasiparticles. Their further control over novel valley degree of freedom (DOF) has offered considerable potential for developing active topological optical devices towards information processing. Here, employing a two-dimensional (2D) valley-Hall perovskite lattice, we report the experimental observation of valley-polarized topological exciton-polaritons and their valley-dependent propagations at room temperature. The 2D valley-Hall perovskite lattice consists of two mutually inverted honeycomb lattices with broken inversion symmetry. By measuring their band structure with angle-resolved photoluminescence spectra, we experimentally verify the existence of valley-polarized polaritonic topological kink states with a large gap opening of ~ 9 meV in the bearded interface at room temperature. Moreover, these valley-polarized states exhibit counter-propagating behaviors under a resonant excitation at room temperature. Our results not only expand the landscape of realizing topological exciton-polaritons, but also pave the way for the development of topological valleytronic devices employing exciton-polaritons with valley DOF at room temperature.

Energy transfer is a ubiquitous phenomenon that delivers energy from a blue-shifted emitter to a red-shifted absorber, facilitating wide photonic applications. Two-dimensional (2D) semiconductors provide unique opportunities for exploring novel energy transfer mechanisms in the atomic-scale limit. Herein, we have designed a planar optical microcavity-confined MoS 2 /hBN/WS 2 heterojunction, which realizes the strong coupling among donor exciton, acceptor exciton, and cavity photon mode. This configuration demonstrates an unconventional energy transfer via polariton relaxation, brightening MoS 2 with a record-high enhancement factor of ~440, i.e., two-order-of-magnitude higher than the data reported to date. The polariton relaxation features a short characteristic time of ~1.3 ps, resulting from the significantly enhanced intra- and inter-branch exciton-exciton scattering. The polariton relaxation dynamics is associated with Rabi energies in a phase diagram by combining experimental and theoretical results. This study opens a new direction of microcavity 2D semiconductor heterojunctions for high-brightness polaritonic light sources and ultrafast polariton carrier dynamics.

High-quality perovskite film is critical for efficient perovskite solar cells. However, it is still challenging to obtain high-quality perovskites processed with the sequential deposition method since the intercalation between the lead diiodide and formamidinium-iodide-rich salts is always hampered by unfavorable formation pathways. Herein, we report a perovskite seeding approach to tailor the formation pathway by making biguanide-hydrochloride-containing two-dimensional perovskites before formamidinium-iodide-rich salt deposition, which renders the perovskite films exhibiting improved crystallinities and surface morphologies. Specifically, the crystallization of perovskite films is greatly enhanced, and the average grain size is increased by 2.5 times. Meanwhile, this tailored sequential deposition with biguanide-hydrochloride agents has led to the formation of two-dimensional perovskites present at the grain boundaries of the resultant perovskite, serving as a passivation agent. Our results show a good energy level alignment for the resultant perovskite absorbers. As a result, a champion power conversion efficiency of 22.12% is obtained. The nonencapsulated device retains 94.69% of the initial efficiency after 600 h of storage in the air (relative humidity <30% at 25 degrees C). Hence, our finding opens an avenue for fabricating high-performance perovskite solar cells.