Metal-halide perovskites (MHPs) have rapidly evolved into a versatile platform for both high-performance optoelectronics and emerging quantum devices, owing to their tunable electronic structure and strong light–matter interaction.¹–² In this talk, I will present our advances in vacuum processed perovskites as a scalable and highly controllable route toward next-generation devices3. We demonstrate a sixfold increase in deposition rate while preserving film quality and power conversion efficiency, enabling an annealing-free, high-throughput co-evaporation process for perovskite solar cells.4 Fully vacuum-processed architectures, including soft-sputtered transparent electrodes, further enable ultrathin and stable devices with absorber down to 10 nm.5

Beyond photovoltaics, nanometre-scale thickness control allows the realization of perovskite-based Multiple Quantum Wells (MQWs), where carrier confinement and excitonic coupling can be precisely engineered.⁶=7 These structures open access to quantum-confined regimes and tunable emission phenomena not attainable in bulk systems. Together, these results illustrate how thermal evaporation bridges scalable manufacturing with quantum-enabled optoelectronic functionalities.

References.

1) Min, H., et al., Nature, 2021, 598, 44.; Yoo, J.J., et al., Nature, 2021, 590 587

2) J. Li et al., Joule 2020, 4, 1035; H.A. Dewi et Al., Adv. Funct. Mater. 2021, 11, 2100557; J.Li et al., Adv Funct. Mater. 2021, 11, 2103252;

3) Dewi et al, ACS Energy Materials 2025, Li et al, Advanced Energy Materias 2026.

4) Dewi et al. ACS Energy Lett. 2024, 9, 4319-4322

5) L. White et el., ACS Energy Lett 2026

6) Advanced Materials 2021, 33, 2005166; L. White et al. ACS Energy Lett. 2024, 9, 83;

7) L. White, ACS Energy Lett. 2024, 9, 4450. L. White, ACS Energy Lett. 2024, 9, 4450.

Halide perovskite materials are recognized as being the most promising absorber layers for tandem solar cell applications. Silicon/Perovskite tandem devices (Si/PK) are undergoing a revolution the last decade with a power conversion efficiency that surpasses the 35%. However, create a stable, reliable and attractive PV market for this type of devices remain challenging. The main issues to address in Si/PK research field are the upscaling process for the PK material deposition on textured Si wafers and the intrinsic and extrinsic stability of the tandem device.

The key features of a PK deposition process in order to consider the fabrication technique a good candidate for upscaling, are the PK good uniformity and coverage of the textured Si surface, the high deposition rate and the low power and material consumption. Based on these criteria in this talk we will first discuss the strengths and weaknesses of the main deposition categories: i) the wet processes (slot-die, Dr blade, ink jet …), ii) the fully vapor-based techniques (co-evaporation, close space sublimation …) and iii) hybrid processes (dry vapor process followed by wet coating).

We will focus on the close space sublimation (CSS) and the co-sublimation (usually called co-evaporation in the literature) techniques for the deposition of the inorganic precursors used in the two-step processes where the inorganic scaffold is deposited first and then it is converted into a perovskite during a second organic-based deposition step followed by an annealing. The two-step processes studied in our work are the hybrid process and the two-step (sequential) full-vapor process. The majority of the published articles on the vapor-based or the hybrid techniques use the co-sublimation process for the deposition of the inorganic scaffold. Hence very little is known about the CSS technique and its impact on the growth mechanism, the chemical and physical properties of the inorganic scaffold.

In these talk, we will compare the physical properties of the inorganic scaffold deposited by CSS and co-sublimation and we will discuss the critical points that influence the morphology, the crystalline structure and the homogeneity of the inorganic thin film. Our preliminary studies indicate that the choice of halogens, the substrate temperature and the composition of the CSS source has an important impact on the thermodynamic and kinetic properties of the deposited film and consequently on the morphology and crystalline structure of the inorganic scaffold. As a result, in the case of the two-step processes such as the hybrid process or the sequential full vapor process, the overall process duration, the crystalline quality, the physical and chemical properties of the final PK layer are highly influenced by the first inorganic step.

Finally we integrate the PK thin film Si/PK tandem device of 9 cm² active area using three different deposition techniques for the PK material: (i) the full wet PK deposition process on chemically polished and nano-textured Si wafer, (ii) hybrid process and (iii) two-step full vapor process using co-sublimation and CSS deposition on fully textured Si wafer. We compare the photovoltaic parameters and the stability of tandem devices and we discuss the main challenges to overcome in order to address the main stability issues and upscale drawbacks in the case of fully textured Si/PK tandem solar cells.

Photoluminescence (PL) imaging has long been used to map optoelectronic properties in perovskite solar cells [1]. Recent PL imaging at millimetre length scales has revealed significant spatial heterogeneity across full device areas, including local variations in recombination and charge-collection quality [2,3]. PL imaging is now an established diagnostic tool for single-junction perovskite solar cells [1,2,4], providing a complementary perspective to microscopic techniques and enabling direct assessment of uniformity, scalability, and processing strategies. Extending PL imaging to tandem architectures enables junction-resolved analysis of performance losses, sequential-deposition effects, and behaviour under electrical bias. However, multijunction devices present significant experimental challenges, requiring both selective excitation of individual junctions and spectral isolation of their emission. While achievable in two-junction devices [5,6], the challenge increases substantially with additional junctions. Here, we present a PL imaging system for simple, rapid, junction-selective characterisation of all-perovskite tandems with up to four junctions. Selective excitation is combined with filtered visible and infrared detection to isolate emission from individual absorber layers. This enables separate photoluminescence quantum efficiency (PLQE) measurements for each junction and spatially resolved comparison across a 0.25 cm² device area. From the PLQE, we can extract quasi-Fermi level splitting (QFLS) maps for each junction, allowing direct comparison between single-junction reference devices and the same perovskite absorbers after tandem integration. This reveals how incorporation into a multijunction stack changes both the magnitude and spatial uniformity of internal optoelectronic properties. In two-junction all-perovskite tandems, the method separates the contributions of the wide- and narrow-bandgap junctions, providing a clear picture of junction-dependent recombination and voltage loss. In three- and four-junction all-perovskite tandems, junction-selective imaging remains possible despite the increased spectral complexity, enabling spatially resolved analysis of PLQE and QFLS for each layer. These higher-order tandem devices show clear QFLS losses in the wider-bandgap materials compared with their single-junction counterparts, indicating sequential-processing-induced open-circuit voltage losses in the top junctions. This is the first example of PL imaging in all-perovskite tandems beyond two junctions, demonstrating the feasibility of spatially resolving optoelectronic properties in complex multijunction devices. The approach provides a practical route to diagnose voltage and recombination losses layer by layer, accelerating the optimisation of next-generation all-perovskite photovoltaic architectures.

The long-term operational stability of perovskite solar cells is critically governed by the chemistry and electronic structure of buried interfaces between metal halide perovskites and charge transport layers. Developing scalable inorganic metal oxide contacts therefore requires a fundamental understanding of interface formation, defect generation, and energy level alignment during both perovskite growth and oxide deposition. Here, we present a systematic photoemission spectroscopy investigation of buried metal oxide/perovskite interfaces using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES), and photoluminescence imaging.

We first investigate the NiOₓ/perovskite interface in inverted (p-i-n) architectures and reveal that a redox reaction between NiOₓ and the perovskite leads to the formation of metallic nickel (Ni⁰), accompanied by interfacial defects and A-site cation deficiency. Surface functionalization with the MeO-2PACz organic molecule suppresses Ni⁰ formation, mitigates interfacial defects, and improves device performance [1]. We then examine the reverse configuration, where NiOₓ is deposited directly onto the perovskite by atomic layer deposition (ALD). Direct oxide growth induces chemical degradation at the buried interface, whereas an ultrathin PTAA interlayer efficiently suppresses precursor-induced reactions and improves device stability [2].

Extending this approach to ALD-grown SnO₂ electron transport layers, we show that direct deposition of SnO₂ induces interfacial defect formation and an electron extraction barrier resulting from chemical reactions between the ALD precursor and the perovskite surface. Introducing an ultrathin PCBM interlayer effectively suppresses these reactions, demonstrating a general strategy for protecting perovskite surfaces during oxide deposition [3].

Building on these findings, we establish a general design principle by comparing wide-bandgap formamidinium- and cesium-based perovskites exposed to oxide deposition by both ALD and pulsed laser deposition (PLD). While formamidinium-based perovskites undergo pronounced chemical degradation, cesium-based compositions exhibit remarkable chemical robustness and favorable electronic interface formation. Together, these results provide unified design rules for engineering chemically stable and electronically optimized metal oxide/perovskite interfaces, enabling scalable fabrication of durable, high-performance perovskite solar cells.

In many emerging solar cell technologies, it is a significant challenge to extract the electronic properties of materials and interfaces inside a working device from experimental data. Traditionally, the properties of materials or interfaces within a device are directly measured using advanced characterization methods. However, most methods applied to individual layers measure the properties of the material in isolation, not in the context of the device. Methods that measure the properties of the entire device cannot measure the properties of the individual layers and hence cannot identify which of the layers in a device stack might be the root cause of underperformance in a device under study. To circumvent the challenges in insight generation we implemented a method for parameter estimation using Bayesian Inference with accelerated sampling (BIAS) and demonstrated its capabilities by extracting physical parameters from illumination dependent current-voltage data of a perovskite solar cell (PSC). This insights can then be used to make informed decisions about strategies for process and material innovations.

Perovskite-based multi-junction photovoltaics are emerging as a promising pathway to surpass the efficiency limits of single-junction silicon technology while maintaining compatibility with industrial manufacturing. This contribution will present recent advances from CSEM and collaborators on high-efficiency 2-terminal perovskite/silicon tandem and perovskite/perovskite/silicon triple-junction solar cells, with particular emphasis on scalability, efficiency, sustainability, and long-term operational durability.

A central focus will be placed on the development of industry-compatible fabrication approaches for both the perovskite absorber and front-side metallization. We will demonstrate that replacing the thermally evaporated metal grid typically used in laboratory-scale devices with screen-printed electrodes results in only minimal performance losses, enabling power conversion efficiencies exceeding 33%. Furthermore, the use of low-silver-content metallization pastes will be shown to have only a limited impact on device performance while significantly improving material sustainability.

Beyond efficiency and scalability, the presentation will address the critical challenge of durability. Recent cell- and module-level developments that enhance resilience under thermal cycling and elevated-temperature light-soaking stress conditions will be presented. These results will be complemented by an overview of the dominant degradation mechanisms affecting perovskite-based multi-junction devices and the mitigation strategies required to achieve the operational lifetimes demanded for commercial deployment.

Together, these advances illustrate the rapid progress toward highly efficient, scalable, and durable perovskite-based tandem and triple-junction photovoltaic technologies, bringing them closer to industrial implementation.

Perovskite-silicon tandem solar cells are now entering into commercial production, but present several manufacturing challenges. Some of these challenges arise from the limited thermal processing budget of the metal-halide perovskite sub-cells, where the halide perovskite itself and organic charge transport layers readily undergo degradation when processed at >100 C for extended periods of time. In this talk, I discuss the possibilities enabled through the use of spatial atomic layer deposition (SALD) for depositing oxides used as buffer layers, encapsulation, and transparent conducting electrodes in perovskite-silicon tandems. 

SALD allows the growth of oxide thin films with similar conformality, uniformity, density and electronic properties as conventional ALD, but with an order of magnitude shorter processing time [1]. This is achieved through the spatial separation of the organometallic and oxidant precursors in a gas manifold, where the substrate (e.g., perovskite device) is oscillated repeated through the gas channels, and the number of oscillations controls the thickness of the film. Such a growth method does not require vacuum, and can readily be scaled-up to grow over large area (e.g., see nanoprintinnovations.com). By shortening the processing time, we demonstrate how a wider range of processing temperatures can be used to grow oxide buffer layers onto perovskite devices, even thermally-sensitive compositions. These oxides include n-type oxides for p-i-n structure solar cells, as well as p-type Cu₂O films for n-i-p structured perovskite solar cells, and we show that these oxides successfully protect the device from mechanical damage during sputter deposition of the transparent top electrode. 

Another critical layer in tandems is the recombination contact required to monolithically connect sub-cells together electrically. We demonstrate the use of SALD to grow H:In₂O₃ thin films, where we achieve 7.2 Ohm/sq sheet resistance. Commercial sputter-deposited indium tin oxide has 13 Ohm/sq sheet resistance, and a transmittance that diminishes toward the near-infrared (NIR). By contrast, H:In₂O₃ achieves low resistivity through high mobility rather than high carrier concentration, and we show that the NIR transmittance is maintained at 89%, important for minimising parasitic optical losses to the low-gap sub-cell. We use nano-SIMS, TEM-EDX, XPS and ToF-ERDA measurements to understand the doping mechanism in H:In₂O₃.

Finally, I will discuss our emerging efforts at using nanolaminate oxide layers grown by SALD for encapsulation. With a stack of 5 layers of AlO_x and ZnO grown at 100 C, a water vapour transmission rate of 10^-5 g m^-2 day^-1. Using this stack on top of a perovskite solar cell that is encapsulated with glass improves the damp-heat stability from T₈₀ after 1200 h (without nanolaminate stack) to T₁₀₀ after 1200 h (with nanolaminate stack).

Overall, this talk demonstrates the utility of SALD for perovskite-based tandem fabrication to improve efficiency and stability. 

Halide perovskite solar cells (PSCs) have revolutionized the photovoltaic landscape, with conventional single-junction cells (typically employing regular-bandgap absorbers of ~1.55 eV) achieving certified power conversion efficiencies (PCEs) exceeding 28%, directly rivalling crystalline silicon. Concurrently, monolithic two-terminal (2T) all-perovskite tandem solar cells, which combine a wide-bandgap (WBG, 1.77~1.78 eV) top subcell with a narrow-bandgap (1.22~1.25 eV) Sn-Pb bottom subcell, represent one of the most compelling routes to surpass the Shockley-Queisser limit of single junctions. State-of-the-art all-perovskite tandems have reached certified efficiencies of 30.1%, while triple-junction architectures have surpassed 28%, demonstrating the vast potential of perovskite photovoltaics. Despite these milestone efficiencies, both single-junction PSCs and WBG tandem subcells are still hindered by critical material-level and interfacial bottlenecks that limit their theoretical efficiency limits and long-term operational lifespan: (i). 1.55 eV Single-Junction PSCs: These devices are primarily constrained by non-radiative recombination at deep-level bulk defects (e.g., undercoordinated Pb²⁺, halide vacancies) and severe carrier loss at the perovskite/charge transport layer (CTL) interfaces (PVK/SAMs or PVK/C₆₀). Furthermore, the structural instability of the highly efficient α-FAPbI₃ phase under moisture or thermal stress remains a key barrier to commercial-grade long-term stability. (ii). WBG Tandem Subcells: Mixed-halide compositions (FA_xCs_1-xPbI_yBr_1-y) are preferred for top subcells but suffer from two unique interrelated challenges: photo-induced phase segregation: Under solar illumination, spontaneous halide demixing creates iodide-rich, low-bandgap domains that trap charge carriers, driven by low halide interstitial migration barriers. Severe open-circuit voltage losses: WBG cells exhibit huge Voc deficits (>200 mV loss for 1.77 eV), primarily due to non-radiative recombination at the critical perovskite/C₆₀ interface.

In this work, we will present our most recent results on the fabrication and testing of WBG and PSC sub cells, their performance and strategies towards additive engineering to enhance stability.  

Perovskite–organic tandem solar cells have emerged as one of the most promising thin-film photovoltaic technologies. Although their efficiencies have only recently begun to rival those of all-perovskite tandems, their greatest advantage may lie in their potential for superior operational stability. In particular, all-perovskite tandem solar cells remain subject to the fundamental stability limitations associated with tin-containing narrow-bandgap perovskite absorbers. For organic solar cells based on PM6 and non-fullerene acceptors (NFAs), we demonstrated early on their potential for excellent photostability under the spectrally filtered illumination conditions encountered in perovskite-organic tandem devices.^1,2 Building on our observations, we unravelled the mechanisms governing the wavelength-dependent stability of PM6 organic solar cells. Upon illumination with photons below a critical wavelength of approximately 500 nm, we observe twisting of the PM6 backbone, which initiates the aggregation of Y6 and is accompanied by an increase in its π–π stacking distance. These structural changes ultimately compromise the extraction and transport of photogenerated charge carriers. The pronounced spectral dependence of this degradation pathway eventually explains why PM6:NFAs cells can reach operational lifetimes of several thousand hours under one-sun illumination while exhibiting virtually no performance degradation under tandem-relevant illumination conditions. Beyond photostability, resilience against other technologically relevant operating conditions, e.g. elevated temperatures and exposure to ambient air, is essential. This is especially important for thin-film perovskite tandems as the narrow-bandgap subcell typically terminates the device stack and is therefore particularly exposed to the environment. Under these conditions, PM6 again emerges as the critical weak link.³ Its benzo[1,2-b:4,5-b′]dithiophene (BDT) units undergo photo-oxidation in the presence of oxygen. Moisture exposure, by contrast, induces reversible twisting of the PM6 backbone, which proves considerably less detrimental to device performance. Interestingly, the oxygen-induced photo-oxidation is largely independent of the photon energy. We pinpoint the underlying mechanism to most likely involve reactive triplet oxygen species, generated through excitation from the charge-transfer state. Consequently, unlike the wavelength-dependent degradation pathway observed under inert conditions, photo-oxidation in ambient air is highly detrimental under both single-junction and tandem operating conditions and therefore requires effective mitigation. To address this challenge, we developed PM6 solar cells incorporating an atomic-layer-deposited nanolaminate barrier.⁴ The fabrication of this barrier, as well as operation under damp-heat conditions, requires the device to withstand elevated temperatures. We identify the limited thermal resilience of the conventional device architecture below 120 °C as originating primarily from the thermal instability of the bathocuproine electron extraction interlayer. By replacing this layer with Al:ZnO nanoparticles as the electron-extraction layer, we achieve the thermal robustness required for subsequent nanolaminate deposition, which ultimately enables, the first damp-heat-stable NFA-based organic solar cell - without the need for additional encapsulation. We therefore conclude that an PM6:NFA based solar cell does carry immense stability promise under multiple harsh stressors, especially in a case where it is combined as a narrow-gap subcell in a tandem with a wide-gap device that acts as a spectral filter for the incident light.

As perovskite/silicon tandem solar cells approach their practical efficiency limit (35.2% experimentally vs. a 39.5% practical potential),[1,2] research focus is increasingly shifting toward scalable manufacturing and operational stability. Residual tensile strain in the perovskite layer remains an intrinsic challenge, arising from the mismatch in thermal expansion coefficients between the perovskite absorber and the silicon substrate.[3] This strain lowers the defect formation energy of halide vacancies, thereby accelerating device degradation.[4] Buried‑layer engineering, specifically introducing a thin 3D inorganic perovskite layer with a smaller lattice parameter than the photoactive perovskite, has recently been shown to counteract this tensile strain by imposing an external compressive strain.[5] Yet, the underlying deposition processes remain challenging to reproduce: cumbersome pure single crystal synthesis, in-situ annealing during thermal evaporation, and need for high post-annealing temperatures (200°C); thus limiting the broader technology transfer.

In this work, we develop a post-treatment-free thermal co‑evaporation process to deposit a 10 nm CsPbCl3 inorganic 3D perovskite layer beneath a 1.68 eV FA_0.85Cs_0.15Pb(I_0.78Br_0.22)₃ photoactive absorber. The study systematically (1) maps the processing window required to obtain phase pure CsPbCl₃ by tuning the CsCl/PbCl₂ co evaporation rate ratio, assessed using XRD and steady-state PL; (2) investigates chlorine diffusion into the FA_0.85Cs_0.15Pb(I_0.78Br_0.22)₃ absorber as a function of the CsPbCl₃ post annealing temperature using ToF-SIMS; and (3) analyzes the charge extraction mechanism at the FACs/CsPbCl₃/hole-transport-layer interface by optimizing the buried‑layer thickness and applying a combination of UPS, KPFM, transient PL, and device-level characterization (Suns-V_OC and Suns-PL). In situ Bragg-Brentano XRD provides mechanistic insight into how the engineered inorganic layer modifies the crystallization pathway of the photoactive perovskite. Complementary grazing incidence XRD reveals the changes in residual strain within the target device stack. The derived design rules enable a scalable fabrication approach compatible with front side-textured silicon wafers featuring industry‑standard pyramid heights (> 2 µm), typically used in fully-textured perovskite/silicon tandem solar cells,[6] and presents a promising step towards stable and scalable next generation photovoltaics.

Monolithic perovskite-silicon tandem solar cells are promising next-generation photovoltaic devices, yet they pose unique characterization challenges that go far beyond established silicon and thin film photovoltaic metrology, mainly through the combination of i) tandem and ii) perovskite-specific absorber and contact aspects. Two external contacts provide access only to the sum of subcell voltages and the minimum of subcell currents, while the current-limiting subcell cannot be identified directly. Mobile ions cause metastability that makes device parameters depend on preconditioning, scan speed, and spectrum, and poor and strongly operation-dependent charge carrier conductivities can introduce non-ohmic transport losses. Critically, the perovskite subcell can operate as a depleted PIN-type device - lacking a quasi-neutral bulk region and exhibiting high-injection conditions in the contact regions - thus violating fundamental boundary conditions of the classical diode model, rendering standard equivalent circuit-based loss analyses inapplicable. This contribution connects these physical effects to analysis methods and shows how they can be transferred to industrially viable measurement procedures.

We address the fill factor deficit that currently separates practical tandem cells from their theoretical limit. Drift-diffusion simulations show that charge carrier resistivity in the perovskite bulk couples to recombination in a voltage- and illumination-dependent way. We call this modulated transport loss. It appears as a photoshunt in illuminated J-V curves that is absent in the dark, a quasi-Fermi level splitting that already exceeds the terminal voltage near the maximum power point, and a voltage-dependent apparent series resistance. The two-diode model cannot reproduce these features. We therefore introduce the Modulated Resistance Model (mod-R), which replaces the empirical second-diode ideality with a physically motivated dark-conductivity parameter. The mod-R agrees well with drift-diffusion results across wide variations of cell parameters.

For subcell-resolved analyses, we use Suns-V_oc and Suns-PLI to extract pseudo and implied open-circuit voltages and fill factors of each subcell separately, which allows quantitative separation of recombination, transport, and selectivity losses. Photoluminescence imaging yields spatially resolved maps of implied voltage and series resistance. As a contactless method, it enables subcell-selective shunt detection by exploiting the voltage coupling between subcells. The method is validated by device simulations and extended to triple-junction cells.

Finally, we demonstrate industrially compatible implementations. LED-based EQE extracts spectral response within seconds using multi-channel simulators. For J-V measurements, open-circuit preconditioning above two seconds stabilizes anion distributions and minimizes hysteresis artifacts. Most relevant for production, we present a millisecond subcell current measurement that uses the silicon bottom cell capacitance as a charge reservoir. An ultrafast reverse sweep after short preconditioning traverses both subcell-limited regimes, yielding individual short-circuit currents from a single measurement. Results on encapsulated industrial tandem cells match spectral metric analyses and show high reproducibility without cell degradation.

In this presentation I will discuss the multiple ways how monolithic perovskite/silicon tandems can be fabricated, built from textured silicon heterojunction solar cells, with an emphasis on the processing of the perovskite top cell. This will be followed by a discussion how bulk and contact passivation of the perovskite are instrumental to obtain a high performance and improving the stability of perovskite photovoltaics, which remains a significant concern for true commercialization. Finally, I will map out the path towards triple-junction perovskite/perovskite/silicon tandems as the ultimate industrial high-performance photovoltaic technology.

Perovskite solar cells (PSCs) have emerged as one of the most promising next-generation photovoltaic technologies owing to their high power conversion efficiencies, low-cost fabrication, defect tolerance, and compatibility with flexible and lightweight substrates. Despite rapid advances in device performance, operational stability remains a major challenge to their widespread commercialization. Among the various degradation mechanisms affecting PSCs, reverse-bias-induced degradation has attracted increasing attention because photovoltaic modules operating under real-world conditions are frequently subjected to reverse-voltage stress caused by partial shading, and cell mismatch. Reverse bias accelerates several degradation processes in PSCs, including ion migration, interfacial charge accumulation, and chemical decomposition of the perovskite absorber and charge transport layers. Furthermore, localized heating under reverse-bias conditions can induce thermal degradation, phase segregation, electrode corrosion, and mechanical failure, significantly reducing device lifetime. While some of these degradation processes are reversible, others cause permanent damage that irreversibly compromises device performance.

In this work, we present a comprehensive investigation of the effects of short-term reverse-bias stress on the stability of PSCs using a multimodal characterization approach. Photoluminescence (hyperspectral) and electroluminescence imaging, Kelvin probe force microscopy, and current density–voltage (J–V) measurements were employed to investigate reverse-bias-induced degradation across multiple length scales, from the macroscopic to the nanoscale. The devices were subjected to reverse-bias stress for a short duration (~20 min), and their subsequent evolution was monitored over extended timescales. Our results reveal that reverse-bias stress activates both reversible and irreversible degradation mechanisms. The reversible degradation is primarily associated with ion migration and fully recovers within approximately one hour after the stress is removed. However, reverse-bias exposure also initiates irreversible degradation pathways that continue to deteriorate device performance over time. These irreversible processes degrade the perovskite absorber, damage the interfacial layers, and promote electrode corrosion. The findings provide valuable insights into the mechanisms underlying reverse-bias-induced degradation and establish practical design guidelines for developing more robust and reliable PSCs. By addressing one of the key reliability challenges facing perovskite photovoltaics, this work contributes to the development of durable, high-performance solar cells suitable for large-scale module integration and long-term outdoor operation.