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Perovskite solar cells (PSCs) are the most rapidly advancing photovoltaic technology in terms of power conversion efficiency. An efficiency of 26.1% was achieved in a decade, which is on par with the efficiency of very mature silicon panels. However, PSC commercialisation is partly hindered by the difficulty of scaling these devices without efficiency loss, mostly due to the increasing sheet resistance of the transparent conductive layer substrates and the nonuniformity of the layers when deposited across large areas. Therefore, it is crucial for the commercialisation of PSCs to implement easily scalable deposition processes with low material waste and compatibility with roll-to-roll (R2R) processes to reduce manufacturing costs. Slot-die coating can meet all these requirements, allowing for great uniformity over large areas. The most recent developments in PSC upscaling using slot-die coating as the main deposition process, along with its extension to the R2R process, are reviewed, including a thorough discussion of the slot-die coating process and the theory behind its operating limits. In fact, R2R coating is a very promising strategy for PSC industrialisation, since all processing steps use low-cost materials and scalable processes at temperatures lower than 120 °C, allowing the cost-effective and high-throughput production of PSC devices. [ABSTRACT FROM AUTHOR]

Perovskite Solar Cells (PSCs) are well known for their high efficiencies under 1 sun (AM1.5G), however, PSC can also generate power by harvesting the low‐light available indoors. Here, three flexible PSC architectures are presented for indoor applications: with a metal electrode aiming for high efficiency; carbon electrode aiming for high stability and compatibility with large‐scale production; and hole transport material (HTM)‐free carbon for simplifying the fabrication process. A maximum efficiency of 30.9% (30.0%) under 1000 lux (200 lux) is obtained for a PSC with gold electrode. A maximum efficiency of 25.4% (24.7%) and 23.1% (22.3%) is obtained for the carbon devices with and without HTM, respectively, under 1000 lux (200 lux). To the best of the author's knowledge, the efficiency values presented here for a device with a carbon‐based electrode, with and without HTM, are the record values for a flexible PSC at indoor light conditions. Furthermore, the HTM‐free carbon device kept 84% of its initial efficiency after 1000 h at MPPT and lost virtually no performance after 1000 h at 85 °C. Also, non‐encapsulated devices of all configurations withstood 1600 h in air with a maximum loss in efficiency of 6%. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have experienced a rapid development during the past decade. For regular PSCs, device efficiency has reached already a power conversion efficiency (PCE) of 25.5%. Inverted PSCs have been attracting increasing attention owing to their easy fabrication, cost‐effectiveness, and suppressed hysteresis characteristics. A maximum PCE of 23.72% for these types of devices is already achieved and some recent progresses in their performance suggest that inverted PSCs are still far from being fully optimized. Great opportunities for reaching simultaneously high stability and efficiency are forecast. Within this work, the most recent developments concerning solar device structure, fabrication of perovskite films, hole and electron transport materials, and electrode contacts in inverted PSCs are overviewed. This work also focuses on stability issues, fabrication methods for large‐area inverted PSCs, encapsulation techniques, economic assessment, and environmental opportunities for hastening inverted PSCs for commercialization. [ABSTRACT FROM AUTHOR]

Hybrid organic–inorganic perovskite materials have become one of the most studied classes of light‐harvesting materials due to their exceptional properties such as high light absorption, long carrier diffusion lengths, bandgap tuning and defect tolerance. Since 2009 that the scientific community has been working on improving the power conversion efficiency (PCE) of perovskite solar cell devices, reaching now an impressive value of 25.5%. Moreover, efficiencies over 18% are often reported by several authors. Since the efficiency goal is almost fulfilled, the scientific community is currently addressing five challenges, with the ultimate objective to make this technology competitive and turn it commercial; these challenges are cost, stability, upscaling, safety and environmental impact. Given the astonishing progresses reached during the past decade and the numerous research groups working to the same goal, it is a matter of time until commercial perovskite solar devices become a reality. In this review work, the most recent achievements regarding this purpose are put together and compared, so as to suggest the most suitable perovskite solar fabrication processes and materials to produce commercial devices. [ABSTRACT FROM AUTHOR]

Summary: Perovskite solar cells (PSCs) are an emerging solar cell technology that has shown the fastest growth in power conversion efficiency (PCE). The present power conversion efficiency record of 25.5% is already comparable to crystalline silicon technology, which is attracting the research and industrial community attention. The main challenges in scaling‐up PSCs are the limited conductivity of the transparent electrode and the difficulty in depositing an uniform and defect‐free perovskite layer over large areas. This work reports the use of engraved gold metal lines in the FTO glass substrate for increasing its electronic conductivity; the prepared 5 cm2 PSC displays a PCE enhancement of 26% over the cells prepared with pristine FTO substrates. [ABSTRACT FROM AUTHOR]

Summary: Perovskite solar cells are one of the most promising photovoltaic technology, presenting the fastest power conversion efficiency (PCE) growth from 3.8 % to 24.2 % in just 10 years. However, there are still challenges hindering its commercialization such as the expensive back‐contact made of gold. Carbon‐based materials, mainly carbon pastes made of carbon black and graphite, have already proven to be good candidates as back‐contacts because of their features such as low cost, high conductivity, and high stability. In this work, the replacement of gold back‐contact by a carbon paper with a microporous layer coated with a PEDOT:PSS dispersion is reported. To the best of the author's knowledge, this material has never been reported for perovskite solar cells. A PCE of 9.22 % was obtained, representing 62 % of the PCE obtained for the same cell but with a gold back‐contact. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSC) have emerged as a promising substitute for conventional silicon panels, showing the fastest power conversion efficiency evolution within the photovoltaic field, going from 3.8 % to 23.7 % in a few years. However, PSC thermal stability is still an obstacle to their commercialization. In this study, the temperature effect on mesoporous triple‐cation perovskite solar cells with two different hole extraction materials—2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) and poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA)—is assessed. The cells are exposed to thermal stress between −5 °C and 80 °C and their photovoltaic performance is monitored in situ to reproduce real operating conditions. At low temperatures, the devices present very stable values (average loss <5 %), but as the temperature increases significant decreases in the open circuit potential and short‐circuit current are observed. X‐ray diffraction shows no change in the perovskite crystal structure with temperature. However, electron scanning microscopy and X‐ray photoelectron spectroscopy indicate that temperature has a great impact on the hole extraction layer. The cell performance loss is attributed to the evaporation of additives added to the hole extraction layer to enhance its conductivity. Although the decrease in power conversion efficiency at 80 °C is slightly higher for PTAA cells, spiro‐OMeTAD cells present a higher irreversible loss of (21.6±2.3) % after thermal stress tests, whereas PTAA devices showed only a loss of (8.2±1.6) %. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSC) have recently emerged as a strong contender for the next generation of photovoltaic technologies, having received the attention of the photovoltaic community, both scientists and industry. In few years, power conversion efficiency of PSCs reached already 22%. A broad range of architectures and fabrication methods have been proposed, as well as several perovskite compositions and charge selective layers, suggesting that the performance of these devices is still far from being fully optimized. PSCs still exhibiting stability problems and the most efficient absorbers incorporate lead (ca. 13 mg m -2 ). Moreover, PSCs are sensitive to high temperatures, UV-light, moisture and oxygen: factors that are hindering their commercialization. The present review frames the last attempts for overcoming these challenges addressing degradation mechanisms and outlining the outstanding achievements. This article also reviews the basic working principles of PSCs, addresses new cell configurations, highlights the need of leak-free encapsulation for long-term stability and environmentally safer devices, and discusses new and lead-free absorbers. [ABSTRACT FROM AUTHOR]

A composite SiO 2 /TiO 2 photoelectrode (PE) architecture for incorporating in dye-sensitized solar cells (DSC) was developed aiming to increase the electron mobility, the specific surface area and the transparency. The developed PE is made of a mesoporous SiO 2 scaffold layer covered by a conformal TiO 2 film deposited by atomic layer deposition (ALD). The shrinking core model was used to predict the minimum pulse time required for the complete coverage of the inner SiO 2 scaffold surface area ( ca . 160 m 2 g −1 ). The TiO 2 film thickness proved to be related to two DSC operation regimes: transport limited regime ( D eff ∝ TiO 2 thickness, where D eff is the electron effective diffusivity) and a recombination limited regime ( D eff constant); in the latter regime, the minimum recombination rate constant, k r , resulted in maximum DSC performance. DSCs based on the new PE coated with an optimized TiO 2 film thickness (3.3 nm, 150 ALD cycles) exhibited an average of 11% higher energy conversion efficiency than the standard devices, η = 9.20% vs. η = 8.25% and 10% more transmittance in the visible range. To the best of the authors’ knowledge this is the best reported DSC efficiency using a SiO 2 /TiO 2 architecture. The superior performance exhibited by the new PE was ascribed to: higher surface area and lower electron recombination. The increased recombination resistance was attributed to lower morphological defects and better dye coverage of the TiO 2 layer. This work shows that an ALD deposited TiO 2 film ranging from 3 to 4 nm in thickness is suitable for the dye adsorption and electron transport; when applied over a large surface area scaffold, the TiO 2 nanolayer displayed the same transport abilities as reference TiO 2 mesoporous films. The proposed PE opens the doors to new architectures and the use of new semiconductors with better properties concerning electronic mobility, conduction band energy level, transparency and recombination. [ABSTRACT FROM AUTHOR]

Perovskite solar cells are by far the photovoltaic technology with the fastest efficiency evolution, reaching now the astonishing power conversion efficiency (PCE) of 25.2%. Their advantages cover also color and transparency, extremely low thickness, low cost, simple fabrication methods and versatile designs. Nevertheless, since it is a young technology, there are still several challenges that need to be overcome for making its commercialization feasible. For making perovskite solar modules, the back-contact plays a critical job since it drives and deliveries the low energy electrons to the p contact of the cell. In n-i-p configuration cells, gold is normally used as back-contact, which is expensive and rare. In this work, several commercial carbon papers and application procedures were investigated. The best performing system produced 89% of the PCE obtained with standard gold back-contact. Besides having a much simpler and cheaper application method, other features such as low cost, great chemical and mechanical stability and low electrical resistivity proved carbon papers potential for commercialization. Moreover, when a gold interlayer of 5 nm was applied, the relative PCE increased up to 92%. Image 1 • A PCE record value is reported for a PSC with a carbon paper back-contact. • The application method of the novel carbon back-contact is extremely simple. • The carbon paper features low sheet resistance (0.5 Ω/sq) and near ohmic contact. • A gold thin layer was used to enhance charge extraction at the back-contact. [ABSTRACT FROM AUTHOR]

A set of coumarin dyes with styryl and phenylethynyl π-bridge at the 3-position were tested for dye-sensitized solar cells (DSSCs). The natural product 6,7-dihydroxycoumarin (Esculetin) was used as starting material. Crucial steps for extension of the conjugated system involved Sonogashira and regioselective Heck arylation reactions, yielding highly fluorescent molecules. The photophysical characterization showed that the extension of conjugation via the alkynyl bridge resulted in redshifted absorption and emission spectra relatively to the parent compound. Electrochemical studies revealed that this derivatization resulted in a marked decrease in HOMO energy levels, which had a marked effect on sensitized solar cell performance. The overall conversion efficiency of the phenylethynyl derivatives proved to be significantly superior (ca. 45%) to the vinyl derivatives, with 6a showing a 2% conversion. [ABSTRACT FROM AUTHOR]