Photovoltaic & Optoelectronic Device Group

Abstract:

ABSTRACT The development of stable and spectrally pure green emitters remains a critical challenge for high performance full color displays and solid‐state lighting. In this work, we present a simple and effective approach to fabricate perovskite light‐emitting diodes based on CsPbBr 3 quantum dots confined within a nanoporous silica scaffold. The introduction of linear (n) or branched (t) butylammonium bromide and crown ethers into the precursor solution prior to infiltration induces improved charge injection and transport across the active layer. This dual‐additive approach contributes to a dramatic enhancement in device performance, leading to a highest luminance exceeding 10,000 cd m − 2 , and markedly improved operational stability. The optimized devices exhibit ultrapure green emission centered at 520 nm with a narrow spectral width below 20 nm. The proposed method provides a versatile and scalable route toward bright, spectrally pure, and durable perovskite light‐emitting devices.

Abstract:

ABSTRACT Perovskite solar cells have achieved high efficiencies but remain limited by instabilities. For the opaque metal rear electrode, Au is commonly used to achieve stable operation but is impractical for scalable photovoltaics due to cost. We investigate the effect of a 5 nm chromium (Cr) interlayer beneath low‐cost metals (Al, Ag, Cu) to inhibit metal interdiffusion. Cr/Al electrodes yield devices with high efficiencies (up to 24.7%) and operational stability comparable to reference devices using Au rear electrodes under heat and light stress, with raw material costs reduced by five orders of magnitude. At the front semi‐transparent electrode, through which sunlight will be incident, we identify indium diffusion from indium tin oxide (ITO) as a key degradation mechanism, revealed via depth‐resolved mass spectrometry. We demonstrate that replacing ITO with fluorine‐doped tin oxide (FTO) substantially improves stability. Combining both improvements, FTO with Cr/Al contacts, produces devices retaining >66% of the initial efficiency after >1000 h ageing at 75 °C under simulated sunlight. These results highlight the critical role of electrode selection on perovskite solar cell durability and provide a practical route toward stable and cost‐effective perovskite photovoltaics.

Abstract:

Evaporation-based manufacturing of halide perovskite light-emitting diodes has garnered increasing attention as a promising alternative for addressing issues with conventional solvent-based processing methodologies. Similar to existing organic light-emitting diode processing infrastructures, evaporation-based processing uses vapour-phase precursor transport and deposition, enabling solvent-free synthesis, precise nanoscale thickness control and enhanced patterning resolution. The physicochemical mechanism of such vacuum-based deposition and growth processes, which is radically different from that of solution-based processes, involves complex thermodynamic and kinetic factors regarding solid–vapour–solid transitions. This imposes much more stringent requirements for deposition environment, mandating concurrent advances in the fundamental understanding of evaporation and growth phenomena, as well as deposition equipment design. In this Perspective, we present a chemistry-driven framework for incorporating fundamental physicochemical principles into evaporation-based processing, with the aim of guiding reproducible and scalable perovskite light-emitting diode deposition system.

Abstract:

Strongly-confined perovskite nanoplatelets (PeNPLs) offer opportunities not found in conventional isotropic nanocubes, especially in producing linearly polarized light, as well as enhancing outcoupling through control over the transition dipole moment. But this requires ultrathin nanoplatelets with three or fewer monolayers of PbI₆ octahedra across the thickness, which are challenging to synthesise uniformly, and their luminescence is strongly affected by surface defects. Together, these limit the performance of ultrathin PeNPLs in light-emitting diodes (LEDs). Here, we address these challenges with an ancillary ligand engineering strategy. We demonstrate that ligands with phosphoryl functional groups strongly bind to the perovskite surface, while having an organic backbone that is not sterically bulky ensures high ligand density. By modulating nucleation and growth, these ancillary ligands lead to monodisperse PeNPLs that stack more uniformly when self-assembled into superlattices, with suppressed agglomeration. As a result, from edge-up PeNPL superlattices, we achieve an enhanced degree of polarization, while from face-down PeNPL superlattices, we achieve enhanced outcoupling that results in LEDs with 13.1% external quantum efficiency, the highest reported for ultrathin PeNPL LEDs. This work establishes ancillary ligand-induced synthesis as a decisive route to achieve uniform nanoplatelets with robust orientation control, enabling full utilization of the multifunctionality of anisotropic PeNPLs.