Screen printable mesoscopic triple-stack solar cells are attractive because of its ease fabrication and scalability of perovskite solar cells and modules. We show that this system is also suitable for alternative absorbers such as Sb 2 S 3 .

Correction for 'The long road to outdoor stability: real-world challenges for controlling perovskite materials for solar cells' by Juan José Patiño López et al., Chem. Soc. Rev., 2026, 55, 4648-4706, https://doi.org/10.1039/d5cs01085c.

Perovskite photovoltaics have demonstrated impressive performance in controlled laboratory tests, with power conversion efficiencies as high as 27%, positioning them as promising alternatives to conventional silicon-based solar cells for various applications. However, despite these major advances, operational stability remains a limiting factor for commercial applications. Large-scale implementation requires addressing challenges such as susceptibility to environmental stressors and the need for long-term outdoor stability, which few standardized outdoor testing studies and publications have accurately assessed. In this review, it is suggested that several stressors, such as temperature and irradiance fluctuations, UV-light, humidity, and precipitation have a significant relevance on the long-term stability. The main degradation reactions initiated by these stressors are reviewed for different compositions of perovskite absorbers and charge transport layers. Furthermore, we reviewed recent in situ and/or in operando studies of perovskite materials and devices under controlled conditions, which intend to elucidate reaction mechanisms and/or interactions among the device's layers in state-of-the-art perovskite compositions, which pave the way for a more rational design of stable devices and highlight the importance of developing in situ or in operando studies for each perovskite composition interacting with other materials within the cell stack. For controlling perovskite solar cells (PSCs) and improving outdoor stability, we emphasize strategies such as bulk modifications, interface engineering, and back electrode design, and discuss each specific strategy used in the literature that has been proved in outdoor conditions and its direct effect on device real-world stability. Moreover, additional strategies such as optimized interconnection layouts, protective functional layers, and advanced encapsulation materials are discussed. Additionally, in this work, an assessment of different measurement approaches aligned with international standards such as IEC 61215 and ISOS was carried out across different climate zones. Our analysis reveals a predominant focus on temperate climates in outdoor testing, along with growing interest in correlating indoor accelerated aging data with measured outdoor performance. In particular, tropical climates, with consistently high humidity, temperature, and solar radiation, provide an ideal setting for exhaustive and accelerated stability tests to evaluate strategies for improving perovskite devices. This review also emphasizes the need for expanding outdoor testing in diverse climates, particularly those enabling rapid feedback and decision-making, as a critical step towards ensuring PSC stability and commercial viability.

The rise of screen printable mesoscopic triple-stack solar cells infiltrated with lead halide perovskites is a milestone in the pursuit of scalable perovskite solar cells. This architecture has been developed to benefit from the excellent transport of charge carriers in the perovskite itself. Consequently, it is possible to incorporate a mesoporous insulating zirconia scaffold into the device architecture and prevent shortcuts between mesoporous titania and carbon films. The use of other absorbers besides lead halide perovskites has not yet been thoroughly explored, probably due to the less competitive charge carrier transport properties of other photoactive materials. In this work, Sb2S3 precursors were infiltrated through the mesoscopic stack, and the photovoltaic properties of the solar cells were analysed. A one-step protocol allowed the preparation of an Sb2S3 absorber; however, the solar cells showed poor photovoltaic response. The modification of this procedure by adding a previous infiltration step (two-step protocol) of a PbI2 solution in DMSO significantly improved the infiltration of the Sb2S3 photoactive layer through the mesoscopic stack, which resulted in an increase in its photovoltaic activity. Only small amounts of PbI2 were needed, which resulted in the formation of a small proportion of Pb2SbS2I3. Although this phase was not photoactive, the PbI2 inclusion significantly improved the solar cell performance with negligible hysteresis in the current-voltage curves. Reproducible efficiencies were obtained using volumes of 0.4 M PbI2 solution ranging between 10 and 5 μL with a highest mean power conversion efficiency of 0.57% for 5 μL. The efficiency values were more dispersed for cells prepared with 2.5 μL of PbI2 solution with a mean value of 0.65%, but a champion cell with an efficiency of 0.8% was obtained. However, the condition using 5 μL of PbI2 solution exhibited superior reproducibility and stability, highlighting a trade-off between peak performance and device consistency across the batches. An optimized, minimal thickness of a mesoporous zirconia film increased the photovoltaic activity of devices, thus suggesting a potential route to facilitate infiltration of mesoscopic stacks with non-perovskite fully inorganic materials as absorbers.

Thin and compact nickel oxide (NiO) films were grown by electrodeposition on two transparent conductive oxides (TCOs): (1) fluorine-doped tin oxide (FTO) and (2) tin-doped indium oxide (ITO) using a novel oxygenated aqueous nickel sulfate electrolyte. Different potentiostatic and galvanostatic electrodeposition conditions were selected from a potentiodynamic study where oxygen reduction reaction (ORR) supplied hydroxide ions that precipitated with Ni(II) species forming the desired films. The proposed oxygenated sulfate electrolyte was compared with the state-of-the-art electrolyte used in the electrodeposition of NiO films with applications in photovoltaic devices (i.e., nickel nitrate). A solution chemistry analysis revealed the main electroactive species involved in the formation of a Ni(OH)2 layer before a post-deposition annealing that dehydrate most of the metal hydroxide to its oxide. A XPS analysis demonstrated that annealing increased the NiO surface fraction over Ni(OH)2 compared with fresh samples but always keeping at least a 25 Electrodeposited NiO films from novel electrolyte composed by nickel sulfate as Ni(II) source and molecular oxygen as hydroxide ions source, alternative to nickel nitrate-based electrolytes. Nitrate-based electrolyes produce undesirable products such as ammonia and nitrite when producing hydroxide ions, necessary for electroprecipitation with Ni(II) species leading to the final NiO phase. P-benzoquinone as novel molecular probe to prove the covering degree of NiO films on transparent conductive oxides (FTO/ITO), also supported by FE-SEM study. This good covering degree ensures efficient transport from photoactive layers toward the external circuit. Characterization proves the p-type semiconductor behavior of NiO, thus working as hole transporting layer. High photocurrent response of perovskite-coated NiO layers is obtained compared to electrodeposited NiO prepared from the state-of-art protocols (NiNO3).

The use of chlorinated solvents such as chlorobenzene for PCBM processing in perovskite solar cells (PSCs) raises environmental and occupational safety concerns. Here, anisole is proposed as a green solvent alternative for PCBM deposition in p-i-n PSCs and flexible minimodules. By optimizing the ink concentration, uniform PCBM layers were obtained with an optimal thickness of 38 nm and a low surface roughness of 4.88 nm. This resulted in reduced series resistance (R1 = 12.48 Ω vs. 13.26 Ω for CB) and a lower ideality factor (1.34 vs. 1.41), enabling efficient interfacial charge extraction and power conversion efficiencies up to 15.98%. Devices retained 95% of their initial PCE after 1100 h under ISOS-D1I and showed improved thermal stability (T80 = 96 h), confirming that solvent substitution does not introduce additional degradation pathways. Furthermore, anisole-based inks were compatible with slot-die coating in roll-to-roll processing, achieving 7.04% efficiency in flexible devices. These results highlight anisole as a safer and greener solvent alternative to chlorobenzene, combining high performance, enhanced stability, and scalability, making it a promising candidate for more sustainable perovskite solar cell manufacturing.

ABSTRACT Halide perovskites have become leading candidates for next‐generation photodetectors because of their tunable bandgaps, strong light absorption, high carrier mobility, and compatibility with versatile fabrication methods. As the field has advanced, processing has emerged as a central factor governing the morphology, crystallinity, defect landscape, and interfacial quality of perovskite active layers, and therefore the final figures of merit of the device. This review examines the principal fabrication strategies used for perovskite photodetectors and their heterostructures, with particular emphasis on the relationship between processing route and device performance. Solution‐based methods such as spin coating, hot casting, spray coating, doctor blading, and inkjet printing are discussed alongside single‐crystal growth and hybrid‐integration approaches. Recent progress in solvent engineering, temperature control, gas‐assisted crystallization, and scalable deposition is analyzed in terms of its impact on film quality, charge transport, detectivity, responsivity, and response speed. This review also addresses the growing role of hybrid heterostructures based on perovskites combined with two‐dimensional materials and related functional layers for broadband and high‐sensitivity photodetection. By linking fabrication strategy with structural and optoelectronic outcomes, this review provides a critical perspective on current advances and remaining challenges toward reproducible, scalable, and application‐oriented perovskite photodetectors.

A photoelectrochemical reactor designed and fabricated from ABS using 3D printing with geometric simplicity and modular assembly is presented, which facilitates flexible scaling and easy adaptation to diverse experimental configurations. It is specifically intended for the evaluation of photoelectrodes aimed at green hydrogen production through water photoelectrolysis. The system displays a dual-compartment configuration separated by a gas-selective membrane, enabling precise characterization of PEC (photoelectrochemical cell) devices. The proof of concept demonstrates the functionality of reactor under laboratory conditions, reaching a current Technology Readiness Level (TRL) between 3 and 4, with ongoing development toward higher TRLs through materials optimization and extended stability testing. The reactor represents a promising approach due to its low cost, scalability, compact integration, and potential to enable future solar-powered hydrogen production. Its accessible design makes it particularly suitable for educational environments and training in solar fuel technologies. With a realistic pathway for scaling to higher TRLs, the system serves as a flexible platform for continued innovation. Furthermore, its compact and energy-efficient configuration positions it as a reliable candidate for future integration with autonomous solar setups, supporting decentralized hydrogen generation.

Halide perovskite solar cells are approaching commercialization, with solution processing emerging as a key method for large-scale production. This study introduces a significant advancement: using non-toxic solvents like water and alcohol in perovskite precursor inks facilitated by the protic ionic liquid methylammonium propionate (MAP). MAP effectively dissolves perovskite precursors such as lead acetate and methylammonium iodide, enabling the first stable water-based perovskite precursor ink suitable for one-step slot-die coating. This new ink formulation contrasts with conventional dimethylformamide (DMF) and dimethylsulfoxide (DMSO)-based inks, as evidenced by in-situ grazing incidence wide-angle X-ray scattering (GIWAXS), which revealed an intermediate-free liquid-to-solid transition. In-situ mass spectrometry also showed that organic molecules evaporate during annealing, resulting in a crystalline perovskite phase. Optimization of the solvent mixture to H2O/IPA/MAP enabled successful slot-die coating, yielding perovskite solar cells with an efficiency of up to 10%. This eco-friendly ink reduces toxicity and environmental impact compared to DMF-based inks, offering a longer shelf life and the possibility of using the ink in ambient conditions. This pioneering work represents the first report of a water-based green ink formulation for one-step thin film coating at room-temperature conditions by slot-die coating, highlighting its potential for sustainable commercial applications.

The application of perovskite photovoltaics is hampered by issues related to the operational stability upon exposure to external stimuli, such as voltage bias and light. The dynamic control of the properties of perovskite materials in response to light could ensure the durability of perovskite solar cells, which is especially critical at the interface with charge-extraction layers. We have applied a functionalized photochromic material based on spiro-indoline naphthoxazine at the interface with hole-transport layers in the corresponding perovskite solar cells with the aim of stabilizing them in response to voltage bias and light. We demonstrate photoinduced transformation by a combination of techniques, including transient absorption spectroscopy and Kelvin probe force microscopy. As a result, the application of the photochromic derivative offers improvements in photovoltaic performance and operational stability, highlighting the potential of dynamic photochromic strategies in perovskite photovoltaics.

Room temperature processing of flexible electronics has become of great interest, as it allows for simpler and cheaper methodologies for high throughput manufacturing of printed electronics. This study focuses on the development and characterization of carbon-based conductive pastes made from a combination of graphite (G) and carbon black (CB), in a polymethyl methacrylate (PMMA) polymer matrix. Raw materials were characterized by Raman Spectroscopy, FTIR, SEM and TEM, showing the structural properties, morphologies and particles size which influenced the characteristics of the pastes. By varying the ratios of G/CB (1 to 4), carbon filler content (11.6–20%), and polymer content (1.5–7%), 48 different formulations were fabricated and further analyzed to determine their electrical conductivity as films. This process identified the optimal formulation for each G/CB ratio. Pastes with higher relative graphite content (G/CB ratios of 3 and 4) yielded the lowest resistivities (as low as 0.078 Ω cm) attributed to the effective formation of conductive networks between G and CB. Best-performing pastes were further characterized by sheet resistance, viscosity, adhesion, and scanning electron microscopy (SEM) analysis to understand the microstructure of the films. Flexible electrodes fabricated on PET substrates withstood 6000 bending cycles, thermal stress at 70 °C, and immersion in water, maintaining electrical conductivity. These results have significant implications for the future development of carbon-based conductive materials for room-temperature applications in flexible and printed electronics.

We present a scalable and environmentally friendly approach for fabricating miniaturized electrochemical immunosensors by integrating slot-die/roll-to-roll (R2R) deposition with laser patterning to produce slot-die carbon electrodes (SDCEs) on flexible polyethylene terephthalate substrates. Conductive films of graphite and carbon black were continuously deposited and patterned by laser ablation to define precise electrode geometries, providing a photolithography-free, high-throughput process compatible with industrial-scale production. Gold nanostars immobilized on the SDC working electrodes enhanced electron transfer and enabled robust nanostructured interfaces for biofunctionalization. Using electrochemical impedance spectroscopy with charge transfer resistance as the transduction parameter, the platform enabled label-free detection of C-reactive protein (CRP), a biomarker associated with inflammation and various chronic diseases, including cardiovascular diseases. Physicochemical characterizations (Raman, XPS, UV-vis, SEM, TEM) confirmed the uniform integration of nanomaterials and device assembly. The nanoimmunosensor exhibited a linear response over the range of 0-2 ng/mL CRP, with a limit of detection of 11.5 pg/mL, demonstrating high sensitivity, selectivity, and reproducibility in human serum. These results underscore the potential of this continuous SDCE-based fabrication strategy to accelerate the transition of nanoimmunosensors from laboratory prototypes to scalable point-of-care diagnostics and wearable bioelectronic applications.

The development of photoelectrochemical water oxidation (PEC) systems has gained significant relevance in recent years due to the quest for clean fuels, where green hydrogen is one of the main actors in the energy transition. Particularly, there has been a need for precious metal‐free electrodes and photoelectrodes that demonstrate high efficiency and stability aiming at having large‐scale and low‐cost green hydrogen production systems. This work shows advances toward this goal by using nonprecious catalysts and solution‐processed materials to achieve efficient, low‐cost, and stable photoelectrodes. Specifically, carbon‐based hybrid perovskite photoelectrodes coupled with an earth‐abundant Nickel‐Iron layered double hydroxide (NiFe‐LDH) catalyst (carbon/NiFe‐LDH) are fabricated and evaluated for oxygen evolution reaction (OER). Devices with an active area of 1.1 cm 2 exhibit evaluated over 12 h of continuous operation, a 4.57% ABPE at 0.64 V RHE , and a photocurrent density of 11.71 mA cm −2 at 1.23 V RHE . The incorporation of graphite tape results in a system (C/GT/NiFe‐LDH) that shows an exceptional operational stability over 125 h and efficiency for this type of photoelectrode with a high photocurrent density of 18.07 mA cm −2 at 1.23 V RHE and 8.51% ABPE at 0.67 V RHE .

Scalable fabrication of perovskite solar cells (PSCs) under ambient conditions remains a key challenge for transferring technology from the lab to industry. Herein, an insight‐guided optimization framework is presented that integrates ink rheology control, interfacial engineering, and crystallization management to achieve reproducible, high‐quality perovskite films via doctor‐blade and slot‐die coating. Hydroxypropyl cellulose is employed as a rheological additive to stabilize meniscus formation, suppress pinholes, and enhance film crystallinity. Charge extraction and interface uniformity are improved by introducing a mesoporous Al 2 O 3 scaffold on top of NiO x , which promotes perovskite infiltration and reduces interfacial defects. Finally, an air‐knife quenching step homogenizes solvent evaporation, yielding compact, large‐grained films with superior optoelectronic properties. Together, these strategies enable reproducible PSCs with uniform thickness (210–230 nm), improve fill factor and current density, and achieve efficiencies up to 17% on flexible substrates—all processed in ambient air. Beyond device improvements, the study establishes a methodology that couples rheological mapping with coating dynamics, offering transferable insights into the deposition–crystallization interplay essential for roll‐to‐roll scalable photovoltaics. This work demonstrates that combining polymer additives, mesoporous scaffolds, and quenching‐assisted drying provides a robust route toward ambient, manufacturable PSC technologies.

The optical properties of CsPbBr3 are studied with temperature dependent spectroscopic techniques. The samples are obtained from a method that has 10 % Pb waste compared with conventional ones. The dependence with temperature between 30 K and room temperature of the optical transmittance and photoluminescence is measured. Near bandgap optical properties are governed by structures originated in free excitons. Using the Elliott model for excitonic absorption, the dependence with temperature of bandgap energy and exciton binding energy are obtained. Both increase with temperature increase. Also, the width of the excitonic absorption and the inter-band absorption, which is assimilated to Urbach energy, were studied. Several models are used to extract parameters from these data. The excitonic absorption width follows the Segall model giving an exciton optical phonon interaction as the dominant term at room temperature. From several fittings, an effective optical phonon energy between 23 and 32 meV is obtained. The Urbach energy at 30 K reaches 10 meV which is related to a good crystalline quality of the samples. Several experimental results show that the origin of the photoluminescence is produced by direct recombination of free excitons. The first one is the similarity of the temperature dependence of photoluminescence width with the one of excitonic absorption. The second one is based in the activation energies obtained from the dependence of the integrated photoluminescence with temperature, one of which coincides with Excitonic Biding Energy. The third one is related to the dependence of the Stokes Shift with temperature which corresponds to the Gurioli model of excitonic thermalization. The last one comes from the dependence of the time resolved photoluminescence. Using rate equations, a radiative and non-radiative monomolecular time constant between 32 and 50 ns and an exciton-exciton annihilation rate constant between 1.0 and 6.0 x 10 7 cm(3)/s are obtained.

Full solution-processed Perovskite solar cellsDaniel Ramirez aa Centro de Investigación, Innovación y Desarrollo de Materiales—CIDEMAT, Universidad de Antioquia , Medellín, Colombia.International Conference on Hybrid and Organic PhotovoltaicsProceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV24)València, Spain, 2024 May 12th - 15thOrganizer: Bruno EhrlerInvited Speaker Session, Daniel Ramirez, presentation 165DOI: https://doi.org/10.29363/nanoge.hopv.2024.165Publication date: 6th February 2024Full solution processing of perovskite solar cells (PSCs) has been one of the main enablers for commercialization of this photovoltaic technology. The utilization of versatile deposition techniques such as doctor blade and slot die facilitate uniform and large-scale fabrication, particularly suitable for roll-to-roll processing. This scalable approach not only ensures high throughput but also holds promise for reducing production costs. This can be possible if all the layers are solution processed and if the production method ensures fast processed of drying and crystallization. In the first case, the main limiting factor is the top electrode, however the alternative of having a carbon-based electrode has become a promising option, while for the second case, the use of flash infrared annealing (FIRA) allows the fabrication of PSCs within the second timescale. This talk will present the late results, including limitations and advantages of having direct and inverted PSCs manufactured by doctor blade and slot-die, aiming at having full solution processed devices. Acknowledgements:The authors acknowledge the Colombian SGR for funding the project "Desarrollo y apropiación de tecnologías convergentes para la generación del conocimiento y la infraestructura necesarios para almacenar energía solar en forma de hidrógeno verde, así como para el uso de este vector energético a nivel nacional" © FUNDACIO DE LA COMUNITAT VALENCIANA SCITOnanoGe is a prestigious brand of successful science conferences that are developed along the year in different areas of the world since 2009. Our worldwide conferences cover cutting-edge materials topics like perovskite solar cells, photovoltaics, optoelectronics, solar fuel conversion, surface science, catalysis and two-dimensional materials, among many others.MATSUSPreviously nanoGe Spring Meeting (NSM) and nanoGe Fall Meeting (NFM), MATSUS is a multiple symposia conference focused on a broad set of topics of advanced materials preparation, their fundamental properties, and their applications, in fields such as renewable energy, photovoltaics, lighting, semiconductor quantum dots, 2-D materials synthesis, charge carriers dynamics, microscopy and spectroscopy semiconductors fundamentals, etc.International Conference on Hybrid and Organic PhotovoltaicsInternational Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and OptoelectronicsThe main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and OptoelectronicsThe International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.

The development of low-cost, readily scalable catalytic systems for green hydrogen production is crucial for diverse research and industrial applications. This work demonstrates the facile coupling of carbon/NiFe-layered double hydroxide (LDH) onto flexible polyethylene terephthalate (PET) substrates deposited by blade coating and spray coating techniques. These low-temperature solution processes enable high-throughput electrode fabrication. The resulting carbon electrode exhibits sheet resistance of 25 Omega sq-1, comparable to other state-of-the-art works, and displays excellent adhesion to the substrate and catalyst layer, thereby ensuring system stability. Remarkably, the developed electrode exhibits high catalytic activity for the oxygen evolution reaction (OER), achieving an overpotential of 215.9 and 267.4 mV at 10 mA cm-2 in rigid and flexible substrates respectively, and maintaining its performance even at 10 mA cm-2 for 24 h. This work highlights the potential of this methodology for producing readily transportable, flexible electrocatalytic systems with exceptional performance and minimal surface treatment of the substrate. Additionally, the use of low-cost, readily recyclable PET plastic aligns with the principles of circular economy, promoting the integration of this platform into both research and industrial environments. Electrodes for green hydrogen production are crucial for the progress of this sustainable technology. This research develops a fully solution-processed flexible electrode for the oxygen evolution reaction in water splitting. The electrodes also show high mechanical stability when submitted to 1000 bending cycles, highlighting the potential of this methodology for producing readily transportable, flexible electrocatalytic systems with exceptional performance. image

Fluorine-doped tin oxide (FTO) is among the most used transparent conductive oxides (TCOs) in phototovoltaic devices such as photoelectrochemical and solar cells. Preparation of films on these TCOs can be achieved by several deposition techniques including electrodeposition. Among the several cleaning and activation procedures before a thin film deposition there is the oxygen plasma treatment, which has been successfully applied on several kind of substrate materials. Surprisingly, the use of this step on TCOs previously to the electrodeposition of a film is not a usual practice. Here we present a detailed study on the consequences of oxygen plasma process over FTO electrodes that are subsequently employed in several electrochemical reactions of practical importance. Open circuit potential (OCP) measurements from oxygen plasma treated FTO have proven the resorption of ions and/or solvent molecules in aqueous electrolyte following a pseudo-second order kinetic. Electrochemical reactions were quite sensible to the oxygen plasma treatment, even under mild conditions. In all cases FTO become deactivated for such electrochemical processes independently of the plasma set up employed except for metal electrodeposition. Partial recovering of the electrochemical response of FTO in the ferri/ferro system after annealing at 450 degrees C explains why oxygen plasma process is worthy only for other deposition techniques such as spray pyrolysis where similar temperatures are employed. Electrochemical Impedance Spectroscopy (EIS) analysis revealed a decrease of the majority carrier density (ND). This is mainly attributed to the oxyanion implantation on oxygen vacancies sites during the plasma process thus explaining the loss of activation of FTO. Energy level diagrams reveal the decrease of degeneracy of FTO towards an n-type semiconducting SnO2 film which is also supported by ultraviolet photoelectron spectroscopy (UPS). A band gap energy dependence with the plasma conditions allowed to check the filling of oxygen vacancies on the FTO surface without discard the loss of fluorine. Anodic polarization in acid media proved the impossibility of oxygen vacancies restitution, being the dominating process the partial etching of FTO.