Multimodal electron microscopy of halide perovskite interfacial dynamics | Nature

Download PDF Subjects Characterization and analytical techniques Electronic devices Organic–inorganic nanostructures Abstract Halide perovskite light-emitting diodes promise high-efficiency 1 , 2 , 3 , low-cost optoelectronics, yet their operational instability remains a critical barrier to practical deployment. Here we develop a multimodal in situ electron microscopy approach that integrates four-dimensional scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy and atomic-resolution imaging to directly visualize structural and chemical evolution in a working halide perovskite light-emitting diode with nanometre precision. Our in situ biasing measurements uncover nanoscale structural and chemical transformations initiated at transport layer interfaces, including the formation of metallic lead and lead-rich secondary phases, as well as strain-driven grain fragmentation. On biasing, we observe the partial transformation of the metallic Al contact to insulating AlCl 3 . Crucially, whereas the bulk of the perovskite emitter remains relatively intact, our experiment shows that degradation is localized at interfaces. By comparing in situ and ex situ measurements, these results establish a mechanistic link between interfacial strain, ionic transport and electrochemical reactions in working devices, and provide a broadly applicable framework for nanoscale degradation analysis in complex multilayered optoelectronic systems using multimodal in situ biasing microscopy. Main Halide perovskites have emerged as promising semiconductors for optoelectronic applications owing to their high charge-carrier mobility, long diffusion lengths and facile solution processability. These properties have enabled rapid advancements in perovskite-based photovoltaics 4 , 5 , light-emitting diodes (LEDs) 6 , 7 , photodetectors 8 , 9 and lasers 10 , 11 . Although substantial progress has been made in photovoltaic stability, hybrid perovskite LEDs remain prone to rapid operational degradation compared to conventional inorganic semiconductors, such as silicon and III–V materials 12 , 13 . Electric-field-driven ion migration and interfacial electrochemical reactions at interfaces are widely recognized as critical challenges 14 , 15 , 16 , yet the atomic-scale mechanisms driving structural instability and interfacial failure remain poorly understood. Conventional in situ techniques, such as synchrotron X-ray spectroscopy, offer valuable chemical insight but lack the spatial resolution to capture localized degradation phenomena in nanostructured devices 17 , 18 , 19 . Consequently, developing comprehensive atomic-scale in situ imaging methodologies is crucial for elucidating degradation processes specific to hybrid perovskite light-emitting diodes (PeLEDs) and designing strategies for enhanced device stability. The advent of high-speed detectors has enabled time-resolved in situ electron microscopy, allowing precise stimulus control with outstanding spatial, temporal and spectral resolution 20 , 21 . Early in situ transmission electron microscopy (TEM) studies on perovskite photovoltaics established the importance of field-driven transformations under bias: iodide migration and PbI 2 nucleation with polarity dependence 22 , oxygen exchange at electron transport interface 23 and the bulk amorphization–recrystallization dynamics in perovskite layers 24 . However, these results were typically obtained under static biasing and focused on bulk perovskite layer, without correlative analysis of the evolution of structure and composition at buried interfaces during device operation (for example, illumination and realistic device drive). Here we present an in situ multimodal electron microscopy investigation of PeLEDs using aberration-corrected four-dimensional scanning TEM (4D-STEM) combined with low-dose atomic-resolution imaging and energy-dispersive X-ray spectroscopy (EDX) analysis. We fabricated and analysed a nanoLED device integrated onto a microelectromechanical system (MEMS) chip that enables electrical biasing in situ. Under galvanostatic conditions, we systematically monitored structural, morphological and compositional evolution at emitters, interfaces and cathode contact. Our experiments reveal pronounced lattice distortions at emitter–transport layer interfaces, formation of lead-rich phases and the critical role of halide migration, particularly Cl − , in electrode corrosion and material decomposition. We show that the perovskite device behaves as a nanoscale electrochemical cell under continuous bias, with interface-specific deformation and chemical reactions governing its failure. These in situ, interface-resolved and correlative insights establish a mechanistic foundation for interface engineering and device design strategies aimed at mitigating degradation and improving the long-term stability of perovskite optoelectronics. A batch of sky-blue PeLED devices were fabricated for this study 25 ( Methods ). The