The transition to renewable energy is essential for mitigating climate change, especially in mountainous regions where energy access and climate vulnerability pose challenges. This study explores photovoltaic (PV) system performance across high- and low-altitude sites in Lebanon, Italy, France, and Switzerland using simulations from the Photovoltaic Geographical Information System (PVGIS). Results show that while low-altitude areas typically yield higher annual energy outputs, high-altitude locations demonstrated seasonal advantages, particularly in spring and summer. Solar irradiation was up to 17.2% higher at lower altitudes overall. However, Performance Ratios, ranging from 73.73% to 88.64%, were generally higher year-round in mountainous areas, indicating greater efficiency at cooler temperatures. A strong inverse correlation between Performance Ratio and module temperature highlights the effect of temperature on PV performance. The Capacity Utilization Factor also varied seasonally, with higher values observed at high-altitude sites during certain months of spring, summer, and autumn. This factor strongly correlated with in-plane radiation, emphasizing irradiation’s role in energy yield. Conducted in accordance with IEC 61724 standards, this research supports energy planning in remote regions. The findings underline the importance of both altitude and geography in solar energy performance, offering valuable insights for expanding renewable energy in diverse and challenging terrains.

The integration of electronic devices into wearable applications has revolutionized the way we interact with technology. The utilization of sustainable materials that align with the principles of environmental consciousness makes it more remarkable. In this context, we propose the fabrication of an energy storage device, a supercapacitor, prepared following a "green approach", starting from the substrate used for its fabrication, i.e., various paper-based materials, and continuing through to the final step. The device fabrication was achieved through screen printing, a scalable and efficient technique that enables precise deposition of materials while eliminating waste. The electrode component is carbon-based, offering cost-effectiveness and mechanical durability, while the use of sodium alginate as both the electrolyte and the interlayer represents a significant innovation. By playing a dual role, sodium alginate reduces the need for additional materials, simplifying the manufacturing process and lowering the device's overall environmental impact. Sodium alginate, derived from renewable and sustainable sources, possesses exceptional biocompatibility and eco-friendliness. Its high ion conductivity and excellent film-forming capabilities make it particularly well-suited for flexible and wearable electronic devices. The power of the obtained interdigitated supercapacitor ranged between similar to 880 & micro;W kg-1 and 505 mW kg-1. This approach not only optimizes the device structure but also reduces its ecological footprint, aligning with the growing demand for low-cost green energy technologies and sustainable materials in electronic applications.

Supercapacitors (SCs) stand out as a storage solution owing to their rapid charge transfer, high power density, low weight, and long lifecycle compared to batteries. Among the SC technologies, interdigitated in-plane SCs offer planar design, compactness, durability, and wide temperature range, which all make them ideal choices for device integration. This work demonstrates the pivotal role of a green, sustainable nanocomposite separator synthesized from detonation nanodiamonds (DNDs) and TiO2 nanoparticles in supercapacitor (SC) devices incorporating interdigitated screen-printed carbon electrodes on paper substrates. The TiO2@DND nanocomposite provides mechanical and thermal stability and exhibits a nanoporous morphology that facilitates ion conduction. The synergic effect between TiO2 and DND is maximized through hydrogen annealing, which enhances interfacial coupling and reduces charge-transfer resistance. Consequently, the TiO2@DND separator enables supercapacitors with high energy and power densities showcasing 597 & micro;F cm-2 capacitance and 99% stability after 10 000 cycles, significantly boosting SC performance and durability. These results highlight the potential of nanodiamonds for improving SC devices and potentially also other energy storage technologies.

Indoor photovoltaics harvests energy from light available inside homes and buildings for powering the Internet of Things, wireless sensors and consumer and medical electronics. A major challenge in this field is a lack of standardized testing conditions. Here a team from more than 60 research institutions and companies proposes best practices for evaluating indoor photovoltaic performance and establishing baseline stability tests. We base these recommendations on recent experimental data, published literature, practices used in academic and industrial settings, technical specifications from standards organizations, lighting databases and existing regulations. We outline procedures that begin with the recommendation of a single artificial light source, followed by guidance on setting up measurement systems and a step-by-step guide for conducting measurements and tests. These procedures are consolidated into three checklists. Our aim is to promote accurate measurement of laboratory and commercial solar cells and modules under indoor lighting, facilitating comparability across academia and industry worldwide. A major challenge for indoor photovoltaics is the absence of harmonized testing protocols, standards, and shared performance benchmarks. This Consensus Statement outlines recommended practices for testing and reporting device performance, power, efficiency and stability.

Perovskite solar cells (PSCs) offer exceptional tunability of optoelectronic properties, enabling wide-band-gap absorbers that are highly attractive for semitransparent devices in building-integrated photovoltaics (BIPV). However, challenges associated with stability, scalability, and materials' cost continue to limit their practical deployment, highlighting the pivotal role of hole transport materials (HTMs) in achieving high efficiency and durable device operation. Herein, we report the rational design and synthesis of three novel small-molecule HTMs based on phenothiazine-triarylamine cores, prepared via concise synthetic routes with moderate-to-high yields. The electron-rich, nonplanar phenothiazine scaffold enables suppressed aggregation and favorable energy-level alignment, rendering these materials particularly suitable for wide-band-gap and semitransparent PSCs. When implemented in FAPbBr3-based semitransparent devices, two candidates (SM1 and SM2) achieve power conversion efficiencies comparable to those of the state-of-the-art poly(triarylamine) (PTAA) (PCE = 6.26% and 6.09% for SM1 and SM2, respectively, vs 6.39% for PTAA). Notably, their enhanced optical transparency leads to comparable light-utilization efficiency (LUE) (4.05 and 3.99 for SM1 and SM2, respectively, vs 4.07 for PTAA), with outstanding and superior bifaciality factors (84% and 82% for SM1 and SM2, respectively, vs 81% for PTAA), providing a distinct advantage beyond conventional opaque-PV efficiency metrics. These findings position phenothiazine-based HTMs as promising, cost-effective alternatives to PTAA for scalable semitransparent perovskite solar cells.

Inorganic wide-bandgap CsPbBr3 perovskite is an interesting material to investigate for several opto-electronic devices such as solar cells, detectors and light emitting diodes. Although the 2.3 eV-bandgap limits the achievement of power conversion efficiencies (PCEs) larger than 10 % in opaque perovskite solar cells (PSC), these materials are still promising in several photovoltaic (PV) fields, such as Building Integrated PV and agri-PV, where the semi-transparency of the device stack can represent an additional value. In this work, we developed a deposition process where the use of BMIM-BF4 ionic liquid in PbBr2 deposition helps the formation of CsPbBr3 with improved uniformity and reduced presence of competitive perovskite phases. Finally, we investigated thank to photoemission spectroscopy and in-situ XRD analysis the impact of the light exposure in the bulk and/or at the surface of thin film. Thanks to the ionic liquid addition and light soaking, the PCE was drastically improved up to 6.11 % using transparent top contact. The Average Visible Transmittance of the semi-transparent PSC device stack exceeded 58 % with Light Utilization Efficiency greater than 3.53 %. Finally, we performed different ageing tests in air such as shelf-life, light soaking at MPP and dry-heat demonstrating encouraging results in terms of the long-term stability under operative working conditions.

Interfaces pose significant challenges to the performance and stability of perovskite solar cells (PSCs), as defects and weak interactions at these boundaries can lead to energy losses and degradation. To address these issues, it is crucial to functionalize hole transport materials (HTMs) to effectively manage interfacial defects and enhance charge transfer. This study introduces a carbazole-based hole transport layer (TC-ICA) that leverages halogen bonding (XB) for enhanced interface passivation with the perovskite layer and carboxylic group anchoring to the indium-doped tin oxide (ITO). By combining these functionalities, the TC-ICA material leads to exceptional device stability (99% shelf stability over 320 days of air storage and a T80-lifetime exceeding 1000 h under light soaking) and enhanced efficiency (15.4%), outperforming single-function materials like TC-CA (14.7%) and TC-I (10.7%). This dual-function strategy marks a significant advancement in the quest for high-performance and long-term stable PSCs.

Flexible perovskite solar cells (F-PSCs) are highly promising for harvesting solar energy in various environments, both indoors and outdoors. Nonetheless, one of the main hurdles to the widespread commercial use of F-PSCs is the thermal evaporation of the metal top electrode, a time-consuming process that substantially increases the cost related to both raw materials and fabrication equipment. Consequently, developing effective alternatives is essential for harnessing the full potential of this technology. One promising approach is to replace the top metal electrode with carbon-based materials, which can effectively serve as both the hole transport layer (HTL) and back electrode. These materials are low cost and compatible with inexpensive, simple, and scalable deposition techniques, such as blade coating. However, HTL-free carbon-based PSCs (C-PSCs) currently suffer from power conversion efficiency (PCE) lower than their metal counterparts, due to inefficient charge transfer and collection, associated with an ineffective perovskite (PVK) and carbon electrode interface. By utilizing a suitable HTL between the PVK and the carbon electrode, the charge extraction can be effectively improved and the interfacial recombination reduced. Throughout this work, a screening of suitable hole transport materials (HTMs) was carried out to select the most promising candidate to improve the performance of C-PSCs on flexible substrates. Copper(i) thiocyanate (CuSCN) was employed as the HTL with a wide band gap (3.5-3.8 eV). At the optimized concentration of 10 mg ml-1, a PCE of 9.4% was achieved on 1 cm2 flexible devices. The results obtained were compared with the performance of F-PSCs with gold top electrodes using organic PTAA as the HTL as state-of-the-art reference. The optimization of the HTL allowed for the demonstration of a significant improvement in the performance of the device, which could pave the way for the large-scale commercialization of PSCs with low environmental impact and promising cost-effectiveness.

Driving continuous, low-power artificial intelligence (AI) in the Internet of Things (IoT) requires reliable energy harvesting and storage under indoor or low-light conditions, where batteries face constraints such as finite lifetimes and increased environmental impact. Here, we demonstrate an integrated three-terminal dye-sensitized photocapacitor that unites a dye-sensitized solar cell (DSC) with an asymmetric supercapacitor, leveraging molecularly engineered polyviologen electrodes and bioderived fungal-based membranes. Under 1000 lux ambient illumination, the photocapacitor delivers photocharging voltages of 920 mV, achieving power conversion efficiencies exceeding 30% and photocharging efficiencies up to 18%. Density Functional Theory calculations reveal low reorganization energies (0.1-0.2 eV) for polyviologen radical cations, promoting efficient charge transfer and stable cycling performance over 3000 charge-discharge cycles. The system reliably powers a multilayer IoT network at 500 lux for 72 hours, surpassing commercial amorphous-silicon modules by a factor of 3.5 in inference throughput. Critically, the photocapacitor driven edge microcontroller achieves 93% accuracy on CIFAR-10 classification with an energy requirement of only 0.81 mJ per inference. By eliminating the need for batteries or grid connection, this work offers a proof of concept for high-efficiency, long-lived indoor power solutions that merge advanced materials chemistry with edge AI, demonstrating a practical route toward self-sustaining, data-driven IoT devices.

Indoor photovoltaics (IPVs) harvest ambient light to produce electricity and can cleanly power the rapidly growing number of Internet-of-Things (IoT) sensors. The surge in IPV development, with new proposed materials, devices and products, creates the need to critically evaluate how IPV devices have advanced and to assess their prospects. In this Review, we analyse the status, challenges and opportunities of established and emerging IPV technologies, including metal-halide perovskite, organic photovoltaics, dye-sensitized solar cell and perovskite-inspired materials. Many emerging low-toxicity semiconductor materials could reach IPV efficiencies of up to 50

Perovskite solar cells (PSCs) have achieved power-conversion efficiencies (PCEs) of 27% on rigid glass substrates, yet their flexible counterparts are more attractive for lightweight, portable and roll-to-roll manufacturing applications. Conventional polymer substrates such as PET and PEN, however, are limited by low thermal tolerance, modest barrier properties, and single-use constraints. Here, we demonstrate stainless-steel (SS) foil as a multifunctional application that simultaneously serves as a flexible substrate, conductive bottom electrode, and robust barrier layer, offering high thermal and mechanical stability as well as reusability across multiple fabrication cycles. Our device stack SS/NiOₓ/MEO-4PACz/PEAI/FAPI/3MTPAI/C₆₀/BCP/Cu fabricated via scalable perovskite layer coating achieves PCEs approaching 10% under standard 1-sun illumination. Performance is currently constrained by optical absorption losses in the semi-transparent Cu electrode, which limit photocurrent generation. To address this, we are transitioning to low-temperature sputtered transparent conducting oxides such as indium tin oxide (ITO) and indium zinc oxide (IZO), which offer higher transparency and lower sheet resistance while remaining compatible with roll-to-roll processing. This approach highlights a realistic pathway toward scalable flexible perovskite solar cells (FPSCs) exceeding 20% efficiency, enabling cost-effective deployment in building-integrated photovoltaics, mobile systems, and off-grid power applications.

Flexible perovskite solar cells (f-PSCs) are emerging as a promising technology for a wide range of applications, where flexibility, lightweight, and a high power-to-weight ratio are desirable features. To ensure f-PSCs longterm stability, a suitable encapsulation that provides protection from atmospheric agents (i.e., moisture, water, and oxygen) without compromising the overall flexibility of the device is required. Thermosetting polyurethanes (PUs) arise as promising candidates: they are inert toward the perovskite layer, and their curing reaction can easily be performed at room temperature, directly on the f-PSC. Moreover, minimal modifications on the precursors' skeleton can tune flexibility, barrier properties, and transparency. In this work, a low-cost thermosetting PU resin is successfully implemented as the primary encapsulant for 1 cm(2) f-PSCs. Two encapsulation strategies are proposed: the PU is applied only on the back of the device (i.e., in contact with the metal electrode) or on both the back and the front, onto the PET substrate. Besides preserving the device flexibility (500 bending cycles without any PCE decrement), the double encapsulation strategy ensures for long term stability under a highly damp atmosphere (RH > 75 %), reaching T80 of over 550 h (i.e., 23 days), clearly outperforming the unencapsulated control devices, whose T80 is 6 h.

Beyond traditional rooftop and building-integrated photovoltaics (BIPV), photovoltaic (PV) devices find applications in agrivoltaics, space, and indoor settings. However, the underwater (UW) environment remains largely unexplored. Below 50 m, the solar spectrum shifts dramatically, with only blue-green light (400-600 nm) available. Perovskite solar cells (PSCs), known for their high-power conversion efficiencies (PCEs) and tunable bandgaps, offer potential for this environment. Initially, simulations compared the intensity of the solar radiation based on three models, each based on a different water body, down to a depth of 10 m. The trend of maximum theoretical performance, ranging from 1.5 to 3 eV band gap, was analyzed with respect to depth. In this pioneering study, a wide bandgap PSC, based on FaPbBr3, has been selected to operate underwater. Results were achieved through a complete in-house process encompassing fabrication, encapsulation, and underwater measurement. A 10-day saltwater submersion test of a damaged device confirmed minimal lead release, meeting stringent legal standards for lead in potable water. PV performance was evaluated UW, demonstrating an enhanced conversion efficiency within the first centimeters of water. This enhancement is due to water's optical and cooling properties. This work opens new frontiers for exploration, both for perovskites, traditionally considered unsuitable for humid environments, and for the increasingly human-occupied underwater realm, which is seeing the development of activities such as wine aging and plant cultivation.

Mechanical reliability plays a critical role in determining the durability of flexible electronic devices because of the significant mechanical stresses they experience during manufacturing and operation. Many such devices are built on sheets comprising stiff transparent-conducting oxide (TCO) electrode films on compliant polymer substrates, and it is generally assumed that the high-toughness polymer substrates do not crack. Contrary to this assumption, here we show extensive cracking in the polymer substrates during bending of a variety of TCO/polymer sheets, and a device example — flexible perovskite solar cells. Such substrate cracking, which compromises the overall mechanical integrity of the entire device, is driven by the amplified stress-intensity factor caused by the elastic mismatch at the film/substrate interface. To mitigate this substrate cracking, an interlayer-engineering approach is designed and experimentally demonstrated. This approach is potentially applicable to myriad flexible electronic devices, with stiff films on compliant substrates, for improving their durability and reliability.

Most authors are part of a consortium that meets through the Indoor Photovoltaics Conference (IPVC), which is organized in conjunction with the MENTOR Marie Skłodowska-Curie Actions Doctoral Network. The IPVC is held annually, and brings together groups from academia, companies commercializing indoor photovoltaic (IPV) and Internet of Things (IoT) devices, national laboratories, and equipment manufacturers. More information can be found at https://projects.tuni.fi/mentor/. Another Marie Skłodowska-Curie Doctoral Network (MASAUTO), funded at the same time, also focuses on IoT development, including IPVs, as well as energy storage and low-power memory (http://masauto-net.eu/).

Efficient semi-transparent solar cells can trigger the adoption of building integrated photovoltaics. Halide perovskites are particularly suitable in this respect owing to their tunable bandgap. Main drawbacks in the development of transparent perovskite solar cells are the high Voc deficit and the difficulties in depositing thin films over large area substrates, given the low solubility of bromide and chloride precursors. In this work, we develop a 2D and passivation strategies for the high band-gap Br perovskite able to reduce charge recombination and consequently improving the open-circuit voltage. We demonstrate 1cm 2 perovskite solar cells with Voc up to 1.73 V (1.83 eV QFLS) and a PCE of 8.2%. The AVT exceeds 70% by means of a bifacial light management and a record light utilization efficiency of 5.72 is achieved, setting a new standard for transparent photovoltaics. Moreover, we show the high ceiling of our technology towards IoT application due to a bifaciality factor of 87% along with 17% PCE under indoor lighting. Finally, the up-scaling has been demonstrated fabricating 20cm 2 -active area modules with PCE of 7.3% and Voc per cell up to 1.65V.