Zhiqiang Guan

The development of high-performance narrow-bandgap tin-lead (Sn-Pb) perovskite solar cells (PSCs) is fundamental to surpassing the Shockley-Queisser limit via all-perovskite tandem configurations. Nevertheless, the vulnerability of Sn²⁺ to oxidation in Sn-Pb perovskite films and devices remains a formidable obstacle to achieving superior film quality and competitive power conversion efficiency (PCE). Here, we introduce a bio-inspired antioxidant engineering strategy employing gallic acid (GA) as a dopant and tannic acid (TA) as a surface passivator to separately stabilize the perovskite bulk and interface. GA, a small antioxidant molecule, localizes at the grain boundaries to impart oxidation resistance and suppress the formation of excess SnI₂ impurities. TA, with its larger molecular framework, resides at the film surface to form a robust passivation layer that hinders oxygen intrusion while establishing a dipole that facilitates interfacial charge transfer. The dual-molecule synergy significantly enhances film oxidative stability against both intrinsic (precursor degradation) and extrinsic (neutral oxygen and superoxide) stimuli. Consequently, the Sn-Pb PSCs achieve a champion PCE of 23.46%, enabling a remarkable 29.95% (certified 29.44%) efficiency in monolithic all-perovskite tandems.

Non-geminate recombination in organic photovoltaics (OPVs) forms low-energy spin-triplet excitons (T₁) that are known to result in irreversible, non-radiative relaxations^1,2,3,4,5. Here we experimentally show in an OPV system incorporating a non-fullerene acceptor with a narrowed singlet–triplet gap that T₁ excitons can be redissociated through the interfacial charge-transfer state to form free carriers. We corroborate this by identifying the increased population of free carriers following triplet sensitization of the acceptor in an OPV blend, and illustrate the way in which this mechanism alters the evolution of T₁ and free carrier populations. We reveal how the distribution of orbitals in the molecule and exciton delocalization in aggregates affect the singlet–triplet energetics of the acceptor in the condensed phase, rendering the traffic between T₁ and the spin-triplet charge-transfer state controllable. By introducing this acceptor as a ternary component into other host OPV systems, we manage to recover the triplet-mediated losses and improve OPV efficiencies by maximizing the number of extractable photocarriers. This study deepens our understanding of the fundamentals of OPVs, and shows how to develop future organic optoelectronics by demonstratating the recovery of low-energy T₁ excitons into usable charges for electricity or light generation instead of heat.

Unconventional 1T′-phase transition metal dichalcogenides (TMDs) have aroused tremendous research interest due to their unique phase-dependent physicochemical properties and applications. However, due to the metastable nature of 1T′-TMDs, the controlled synthesis of 1T′-TMD monolayers (MLs) with high phase purity and stability still remains a challenge. Here we report that 4H-Au nanowires (NWs), when used as templates, can induce the quasi-epitaxial growth of high-phase-purity and stable 1T′-TMD MLs, including WS₂, WSe₂, MoS₂ and MoSe₂, via a facile and rapid wet-chemical method. The as-synthesized 4H-Au@1T′-TMD core–shell NWs can be used for ultrasensitive surface-enhanced Raman scattering (SERS) detection. For instance, the 4H-Au@1T′-WS₂ NWs have achieved attomole-level SERS detections of Rhodamine 6G and a variety of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike proteins. This work provides insights into the preparation of high-phase-purity and stable 1T′-TMD MLs on metal substrates or templates, showing great potential in various promising applications.

Given the high energy density and eco-friendly characteristics, lithium-carbon dioxide (Li-CO₂) batteries have been considered to be a next-generation energy technology to promote carbon neutral and space exploration. However, Li-CO₂batteries suffer from sluggish reaction kinetics, causing large overpotential and poor energy efficiency. Here, we observe enhanced reaction kinetics in aprotic Li-CO₂batteries with unconventional phase 4H/face-centered cubic (fcc) iridium (Ir) nanostructures grown on gold template. Significantly, 4H/fcc Ir exhibits superior electrochemical performance over fcc Ir in facilitating the round-trip reaction kinetics of Li⁺-mediated CO₂reduction and evolution, achieving a low charge plateau below 3.61 V and high energy efficiency of 83.8%. Ex situ/in situ studies and theoretical calculations reveal that the boosted reaction kinetics arises from the highly reversible generation of amorphous/low-crystalline discharge products on 4H/fcc Ir via the Ir-O coupling. The demonstration of flexible Li-CO₂pouch cells with 4H/fcc Ir suggests the feasibility of using unconventional phase nanomaterials in practical scenarios.