Alex Kwan Yue Jen

The long-term stability of high-efficiency n-i-p perovskite solar cells is limited by coupled defect migration, residual lattice strain, and thermal–mechanical degradation. Here, we develop a non-ionic, interface-enriched zinc phthalocyanine derivative, 4PCSZnPc, as a molecular stabilizer for simultaneous defect anchoring and strain buffering. Unlike ionic additives that may introduce mobile species, 4PCSZnPc is distributed throughout the film, with enrichment near the buried SnO2/perovskite interface. Peripheral N/O/S heteroatoms coordinate with under-coordinated Pb2+ sites, while the Zn-regulated macrocyclic center interacts with iodide-related defects, forming dual-site Lewis acid–base anchoring. Meanwhile, the rigid phthalocyanine framework reduces residual tensile stress and may hinder strain-assisted ion migration. These combined effects of defect passivation and strain buffering reduce non-radiative recombination, improve film uniformity, and enhance thermal robustness. Consequently, 4PCSZnPc-treated devices achieve a champion power conversion efficiency (PCE) of 26.88% (certified 26.74%), a T80 lifetime of 1358 h under 1-sun at 85 °C, and 95% retention after 200 thermal cycles, providing a design principle for future thermally resilient photovoltaics.

Perovskite‐organic tandem solar cells (PO‐TSCs) offer a compelling platform for flexible photovoltaics by combining wide‐bandgap (WBG) perovskite top cells with mechanically compliant organic rear cells. However, their long‐term stability is critically limited by the intrinsic instability of WBG mixed‐halide perovskites. Here, through systematic ageing and mechanistic analyses, we identify halide phase segregation in the WBG perovskite sub‐cell under photothermal stress as the dominant degradation pathway that dictates the operational stability of the PO‐TSC investigated here. To address this challenge, we develop a halogenated cyclodextrin‐based supramolecular strategy that enables precise regulation of perovskite crystallization, defect passivation and halide distribution. Synergistic host‐guest, hydrogen‐bonding, halogen‐bonding and coordination interactions simultaneously regulate crystallization and suppress ion migration to result in stabilized halide homogeneity. Consequently, 1.80‐eV WBG devices achieve 20.60% efficiency with improved operational stability. Integrated PO‐TSCs deliver an efficiency of 27.17% (certified 26.3%) together with T ₈₀ lifetimes of 1100 h under maximum power point tracking (MPPT) operation and T ₈₅ lifetimes of 1128 h under thermal stress of 85°C, while flexible PO‐TSCs reach an efficiency of 24.00%. This work defines a general supramolecular design paradigm for efficient, durable and flexible tandem photovoltaics.

Multiresonance thermally activated delayed fluorescence (MR-TADF) emitters enable narrow-bandwidth emission and high efficiency in organic light-emitting diodes; however, the fundamental origin of the multiresonance effect remains incompletely understood. Herein, a fine-tuned Uni-Mol model trained on reported MR-TADF emitters identifies BN-embedded aromatic units as the primary structural motif governing small singlet–triplet energy gaps. Wave function-based quantum chemical calculations subsequently validate this prediction and provide a mechanistic understanding of the underlying electronic structure. While the minimal BN-containing unit dictates the singlet–triplet splitting, π-extension primarily controls vibronic stabilization and emission bandwidth. The multiresonance effect is shown to arise from a cooperative interplay of phase-separated orbital topology, suppressed exchange interactions and enhanced excited-state correlation, further reinforced by heteroatom-induced electronic polarization that yields nearly identical S1 and T1 charge distributions. Combined with the data-driven identification of boron positioning as the dominant modulator of singlet–triplet splitting and nitrogen−π coupling as a key determinant of emission color, this work provides actionable design principles for next-generation MR-TADF emitters with controlled spectral purity and near-zero singlet–triplet gaps.

Achieving long operational stability is critical for advancing high-performance organic solar cells (OSCs) towards commercialization. Designing a charge transport layer with optimal electrical-physical-chemical compatibility is a pivotal strategy. Herein, we demonstrate an electron transport layer (ETL) by incorporating in-situ fluorinated carbon dots (FCDs) in a coherent polymer to construct the crystallinity-enhanced FCD network (^netFCD) via strong hydrogen bonding. Uniquely, ^netFCD-based ETLs offer very strong electrical and mechanical contact with their all-sided (cathode and active layer) interfaces. The reduced basicity feature of ^netFCD prevents unexpected interfacial reactions with non-fullerene acceptors. Meanwhile, ^netFCD-based ETLs enable barrier-free devices with high electron mobility and hole blocking. Using the strategically designed ^netFCD with the interesting features as “all-in-one” ETL, the inverted OSCs (i-OSCs) achieve 20.01% PCE (Certified PCE: 19.78%). The OSCs maintained 85% of their initial PCE after 1800 hours of operation under 80 ± 5% humidity while the flexible i-OSCs realized 95% of the initial PCEs after 10,000 bending cycles, advancing the operational (i.e., photoelectrical), mechanical, and environmental stability in OSCs with different structures. This work contributes to developing not only feasible bulk-to-interface interlayer designs but also green and low-cost materials to promote OSCs as sustainable and green energy sources.

Narrow‐bandgap Sn‐Pb perovskites have showcased great potential for constructing tandem perovskite solar cells (PSCs). However, Sn ^{2 +} in Sn‐Pb PSCs is readily oxidized to Sn ^{4 +} , and such B‐site Sn ^{4 +} will introduce excess positive charge and causes severe p‐type self‐doping, which pins the Fermi level and aggravates non‐radiative recombination. Additionally, the Sn‐based component crystallizes far more rapidly than that of Pb, resulting in unbalanced Sn‐Pb crystallization. To address these challenges, we develop a novel n‐type molecule NDBH as perovskite additive. This molecule offers three key advantages: prevents the oxidation of Sn ^{2 +} through chelation and blocks oxygen ingress along grain boundaries; balances the crystallization rates of Sn‐Pb perovskite by selectively chelating Sn ^{2 +} ; modifies the perovskite surface to be more n‐type. With this organic n‐type molecule, the inverted Sn‐Pb PSCs achieve power conversion efficiency (PCE) of 24.11%. The devices also exhibited remarkable long‐term stability, retaining over 90% of their initial efficiency after 600 h of maximum power point (MPP) tracking. This approach of designing multifunctional n‐type molecules offers a new perspective for enhancing the efficiency and stability of Sn‐Pb PSCs.

Formamidinium lead triiodide (FAPbI ₃ ) perovskite solar cells (PSCs) have attracted significant attention due to their outstanding optoelectronic properties. However, their long‐term stability remains limited by lattice strain‐induced transition from the photoactive α‐phase to the nonphotoactive δ‐phase. In this work, first‐principles calculations reveal that the incorporation of Na ⁺ into interstitial sites between adjacent FA ⁺ cations significantly reduces the formation energy of the α‐phase, thereby promoting its thermodynamic stabilization. Then, experimental results confirm that the introduction of 2 mol% Na ⁺ effectively alleviates lattice strain while simultaneously suppressing δ phase. Moreover, the accompanying sulfonate groups interacting with PbI ₂ can regulate the crystallization and improve film quality. As a result, the optimized PSC achieved power conversion efficiency (PCE) as high as 26.67% (certificated 26.44%), ranking among the highest reported for the n‐i‐p structured devices. Notably, the bare device without encapsulation retained over 90% of its initial efficiency after continuous heating at 85°C for 1200 h and maintained 80% after 800 h continuous illumination. This study demonstrates that metal cation doping is an effective strategy for stabilizing the perovskite lattice and enhancing long‐term operational stability of perovskite‐based optoelectronic devices.