Gonzalo del Pozo

Perovskite solar cells are currently well known for both their outstanding advantages and their main drawback: rapid degradation when exposed to external agents. In particular, the sensitivity of these devices to ultraviolet (UV) radiation has been widely reported, where the underlying degradation mechanisms in metal oxide-free p–i–n architectures remain insufficiently understood. In this work, we systematically investigate the impact of UV irradiation (385 nm) on metal oxide-free p–i–n PSCs under inert atmosphere, combining optical simulations, morphological characterization (SEM and AFM), current-voltage analysis, scan-rate-dependent measurements, and impedance spectroscopy. Optical modeling reveals that UV photons are absorbed within the first few tens of nanometers of the perovskite layer, near the hole transport layer (HTL)/perovskite interface. Consistently, SEM and AFM analyses show significant surface restructuring after UV exposure, including grain coarsening and increased roughness. Electrically, degradation is dominated by a severe loss of short-circuit current density, accompanied by a progressive reduction in fill factor, while the open-circuit voltage remains comparatively stable. Detailed DC and AC analyses demonstrate that these effects originate from a coupled ionic-electronic degradation mechanism. UV exposure promotes the accumulation of mobile ions, leading to screening of the internal electric field and impaired charge extraction, while simultaneously generating deep trap states at or near the HTL/perovskite interface that enhance Shockley-Read-Hall recombination. Impedance spectroscopy further reveals increased ionic transport and the emergence of fast interfacial processes associated with trap-assisted recombination. These findings provide a comprehensive mechanistic framework for understanding UV-induced degradation in metal oxide-free p–i–n perovskite solar cells and highlight the critical role of interfacial ion-trap interactions in limiting device stability, even under inert and encapsulated operating conditions.

Perovskite solar cells (PSCs), originally developed for low‐cost photovoltaic energy harvesting, can also serve as versatile platforms for photodetection. However, their intrinsic absorption edge below 800 nm prevents direct response to most of the near‐infrared (NIR) spectrum. Here, we demonstrate that integrating up‐conversion (UC) nanoparticles (NaY ₆₅ Gd ₁₅ F ₄ :Yb ₁₈ ³⁺ , Er ₂ ³⁺ ) enables these devices to function as self‐powered NIR detectors. The nanoparticles, synthesized by a simple hydrothermal route, convert NIR photons into visible emission that matches the perovskite absorption edge. Structural analysis confirmed that particles grown at 220°C with a 15% Gd content crystallize in the hexagonal phase, showing red‐dominated luminescence. Once incorporated into complete perovskite devices, the UC nanoparticles (UCNPs) preserved the baseline photovoltaic response while producing a measurable photocurrent under 980 nm excitation. Our results reveal a practical route to transform PSCs into affordable and scalable devices for infrared sensing.

Perovskite solar cells are one of the most promising photovoltaic technologies in the last decades. Inverted (p–i–n) cells using NiO_X as hole‐transport layer (HTL) have gained attention due to their easy fabrication methods and high stability, although they often exhibit reduced efficiencies due to non onlyoptimized energy‐level alignment. To address this issue, different approaches have been developed, such as the use of self‐assembled monolayers (SAMs) on top of the HTL. Herein, a comparative study between regular p–i–n cells and cells using Me‐PACz as an SAM on top of NiO_X is we presented. Devices with SAM exhibit enhanced open‐circuit voltage and efficiency. Temperature DC and AC characterization reveals that the incorporation of SAM reduces recombination at the interface, as seen from the comparison of the perovskite bandgap (1.6 eV) and carrier activation energy ≈1.1 and ≈1.59 eV for reference and SAM, respectively. Finally, an outdoor degradation experiment with minimodules has been conducted. The experiment spanned for more than 500 days, and results show that minimodules with SAM were less stable than those based on the reference layer structure. This is due to a severe decrease in the short‐circuit current, which could be attributed to a deterioration of the SAM spacer.

Perovskite solar cells are considered to be one of the most promising solar cell designs in terms of photovoltaic efficiency. However, their practical deployment is strongly affected by their short lifetimes, mostly caused by environmental conditions and UV degradation. In this contribution, we present a metasurface made of silver nanoparticles used as a UV filter on a perovskite solar cell. The UV-blocking layer was fabricated and morphologically and compositionally analyzed. Its optical response, in terms of optical transmission, was also experimentally measured. These results were compared with simulations made through the use of a well-proven computational electromagnetism model. After analyzing the discrepancies between the experimental and simulated results and checking those obtained from electron beam microscopy and electron dispersion spectroscopy, we could see that a residue from fabrication, sodium citrate, strongly modified the optical response of the system, generating a redshift of about 50 nm. Then, we proposed and simulated the optical behavior of core–shell nanoparticles made of silver and silica. The calculated spectral absorption at the active perovskite layer shows how the appropriate selection of the geometrical parameters of these core–shell particles is able to tune the absorption at the active layer by removing a significant portion of the UV band and reducing the absorption of the active layer from 90% to 5% at a resonance wavelength of 403 nm.

Bias voltage scan rate and mobile ion concentration have a strong influence in J-V curves of metal halide perovskite-based memristors. In addition to hysteresis, in some cases J-V curves also show an anomalous drop in current known as negative differential resistance. This feature is usually related to electrochemical reactions between the reactive metal and I ^- ions, and to air exposure. However, in devices with low-reactive electrodes, its origin is still under debate. In this work, we propose a theoretical model based on ionic-electronic drift-diffusion. This model sheds light into the ionic-electronic processes that shape hysteresis, and it helps to explain the appearance and evolution of a negative resistance in memristors with low-reactive contacts and capacitive hysteresis. Finally, experimental J-V curves are presented to validate the proposed model.

Perovskite solar cells (PSCs) have become very popular due to the high efficiencies achieved. Nevertheless, one of the main challenges for their commercialization is to solve their instability issues. A thorough understanding of the processes taking place in the device is key for the development of this technology. Herein, J-V measurements have been performed to characterize PSCs with different active layer thicknesses. The solar cells’ parameters in pristine devices show no significant dependence on the active layer thickness. However, the evolution of the solar cells’ efficiency under ISOS-L1 protocol reveals a dramatic burn-in degradation, more pronounced for thicker devices. Samples were also characterized using impedance spectroscopy (IS) at different degradation stages, and data were fitted to a three RC/RCPE circuit. The low frequency capacitance in the thickest samples suffers a strong increase with time, which suggests a significant growth in the mobile ion population. This increase in the ion density partially screens the electric field, which yields a reduction in the extracted current and, consequently, the efficiency. This paper has been validated with two-dimensional numerical simulations that corroborate (i) the decrease in the internal electric field in dark conditions in 650 nm devices, and (ii) the consequent reduction in the carrier drift and, therefore, of the effective current extraction and efficiency.