Predicting the efficiency of luminescent solar concentrators for solar energy harvesting using machine learning.

Building-integrated photovoltaics (BIPV) is an emerging technology in the solar energy field. It involves using luminescent solar concentrators to convert traditional windows into energy generators by utilizing light harvesting and conversion materials. This study investigates the application of machine learning (ML) to advance the fundamental understanding of optical material design. By leveraging accessible photoluminescent measurements, ML models estimate optical properties, streamlining the process of developing novel materials, offering a cost-effective and efficient alternative to traditional methods, and facilitating the selection of competitive materials. Regression and clustering methods were used to estimate the optical conversion efficiency and power conversion efficiency. The regression models achieved a Mean Absolute Error (MAE) of 10%, which demonstrates accuracy within a 10% range of possible values. Both regression and clustering models showed high agreement, with a minimal MAE of 7%, highlighting the efficacy of ML in predicting optical properties of luminescent materials for BIPV.

A comprehensive dataset of photonic features on spectral converters for energy harvesting.

Building integrated photovoltaics is a promising strategy for solar technology, in which luminescent solar concentrators (LSCs) stand out. Challenges include the development of materials for sunlight harvesting and conversion, which is an iterative optimization process with several steps: synthesis, processing, and structural and optical characterizations before considering the energy generation figures of merit that requires a prototype fabrication. Thus, simulation models provide a valuable, cost-effective, and time-efficient alternative to experimental implementations, enabling researchers to gain valuable insights for informed decisions. We conducted a literature review on LSCs over the past 47 years from the Web of ScienceTM Core Collection, including published research conducted by our research group, to gather the optical features and identify the material classes that contribute to the performance. The dataset can be further expanded systematically offering a valuable resource for decision-making tools for device design without extensive experimental measurements.

An autonomous power temperature sensor based on window-integrated transparent PV using sustainable luminescent carbon dots.

The energy efficiency of buildings can be significantly improved through the use of renewable energy sources. Luminescent solar concentrators (LSCs) appear to be a solution for integrating photovoltaic (PV) devices into the structure of buildings (windows, for instance) to enable low-voltage devices to be powered. Here, we present transparent planar and cylindrical LSCs based on carbon dots in an aqueous solution and dispersed in organic-inorganic hybrid matrices, which present photoluminescent quantum yield values up to 82%, facilitating an effective solar photon conversion. These LSCs showed the potencial for being incorporated as building windows due to an average light transmittance of up to ∼91% and color rendering index of up to 97, with optical and power conversion efficiency values of 5.4 ± 0.1% and 0.18 ± 0.01%, respectively. In addition, the fabricated devices showed temperature sensing ability enabling the fabrication of an autonomous power mobile temperature sensor. Two independent thermometric parameters were established based on the emission and the electrical power generated by the LSC-PV system, which could both be accessed by a mobile phone, enabling mobile optical sensing through multiparametric thermal reading with relative sensitivity values up to 1.0% °C-1, making real-time mobile temperature sensing accessible to all users.

Extraction and purification of phycobiliproteins from algae and their applications.

Microalgae, macroalgae and cyanobacteria are photosynthetic microorganisms, prokaryotic or eukaryotic, living in saline or freshwater environments. These have been recognized as valuable carbon sources, able to be used for food, feed, chemicals, and biopharmaceuticals. From the range of valuable compounds produced by these cells, some of the most interesting are the pigments, including chlorophylls, carotenoids, and phycobiliproteins. Phycobiliproteins are photosynthetic light-harvesting and water-soluble proteins. In this work, the downstream processes being applied to recover fluorescent proteins from marine and freshwater biomass are reviewed. The various types of biomasses, namely macroalgae, microalgae, and cyanobacteria, are highlighted and the solvents and techniques applied in the extraction and purification of the fluorescent proteins, as well as their main applications while being fluorescent/luminescent are discussed. In the end, a critical perspective on how the phycobiliproteins business may benefit from the development of cost-effective downstream processes and their integration with the final application demands, namely regarding their stability, will be provided.

Bio-Based Solar Energy Harvesting for Onsite Mobile Optical Temperature Sensing in Smart Cities.

The Internet of Things (IoT) fosters the development of smart city systems for sustainable living and increases comfort for people. One of the current challenges for sustainable buildings is the optimization of energy management. Temperature monitoring in buildings is of prime importance, as heating account for a great part of the total energy consumption. Here, a solar optical temperature sensor is presented with a thermal sensitivity of up to 1.23% °C-1 based on sustainable aqueous solutions of enhanced green fluorescent protein and C-phycocyanin from biological feedstocks. These photonic sensors are presented under the configuration of luminescent solar concentrators widely proposed as a solution to integrate energy-generating devices in buildings, as windows or façades. The developed mobile sensor is inserted in IoT context through the development of a self-powered system able to measure, record, and send data to a user-friendly website.

Protein Cohabitation: Improving the Photochemical Stability of R-Phycoerythrin in the Solid State.

The poor photochemical stability of R-phycoerythrin (R-PE) has been a bottleneck for its broad-spectrum applications. Inspired by nature, we studied a sustainable strategy of protein cohabitation to enhance R-PE stability by embedding it in a solid matrix of gelatin. Both pure R-PE and fresh phycobiliprotein (PBP) extracts recovered from Gracilaria gracilis were studied. The incorporation of R-PE in the gelatin-based films (gelatin-RPE and gelatin-PBPs) has improved its photochemical stability for at least 8 months, the longest time period reported so far. These results were evidenced by not only absorption but also emission quantum yield measurements (Φ). Moreover, the photostability of gelatin-RPE films upon continuous excitation with an AM1.5G solar simulator was tested and found to remain stable for 23 h after initial decreasing up to 250 min. In the end, another approach was established to allow 100% photostability for a 3 h exposure to an AM1.5G solar simulator by doping the gelatin-based film including R-Phycoerythrin with n-propyl gallate stabilized with Tween 80, allowing their use as naturally based optically active centers in photovoltaic applications.

Luminescence Thermometry on the Route of the Mobile-Based Internet of Things (IoT): How Smart QR Codes Make It Real.

Quick Response (QR) codes are a gateway to the Internet of things (IoT) due to the growing use of smartphones/mobile devices and its properties like fast and easy reading, capacity to store more information than that found in conventional codes, and versatility associated to the rapid and simplified access to information. Challenges encompass the enhancement of storage capacity limits and the evolution to a smart label for mobile devices decryption applications. Organic-inorganic hybrids with europium (Eu3+) and terbium (Tb3+) ions are processed as luminescent QR codes that are able to simultaneously double the storage capacity and sense temperature in real time using a photo taken with the charge-coupled device of a smartphone. The methodology based on the intensity of the red and green pixels of the photo yields a maximum relative sensitivity and minimum temperature uncertainty of the QR code sensor (293 K) of 5.14% · K-1 and 0.194 K, respectively. As an added benefit, the intriguing performance results from energy transfer involving the thermal coupling between the Tb3+-excited level (5D4) and the low-lying triplet states of organic ligands, being the first example of an intramolecular primary thermometer. A mobile app is developed to materialize the concept of temperature reading through luminescent QR codes.

Highly Efficient Luminescent Polycarboxylate Lanthanide Complexes Incorporated into Di-Ureasils by an In-Situ Sol-Gel Process.

In order to prepare efficient luminescent organic⁻inorganic hybrid materials embedded with a lanthanide (Ln3+) complex with polycarboxylate ligands, Ln3+-doped di-ureasils with 4,4-oxybis(benzoic acid) and 1,10-phenanthroline ligands were synthesized via an in-situ sol⁻gel route. The resulting hybrids were structurally, thermally, and optically characterized. The energy levels of the ligands and the host-to-ion and ligand-to-ion energy transfer mechanisms were investigated (including DFT/TD⁻DFT calculations). The results show that these Ln3+-based di-ureasil hybrids exhibit promising luminescent features, e.g., Eu3+-based materials are bright red emitters displaying quantum yields up to 0.50 ± 0.05. The luminescent color can be fine-tuned either by selection of adequate Ln3+ ions or by variation of the excitation wavelength. Accordingly, white light emission with CIE coordinates of (0.33, 0.35) under 310 nm irradiation was obtained.

High-Performance Near-Infrared Luminescent Solar Concentrators.

Luminescent solar concentrators (LSCs) appear as candidates to enhance the performance of photovoltaic (PV) cells and contribute to reduce the size of PV systems, decreasing, therefore, the amount of material needed and thus the cost associated with energy conversion. One way to maximize the device performance is to explore near-infrared (NIR)-emitting centers, resonant with the maximum optical response of the most common Si-based PV cells. Nevertheless, very few examples in the literature demonstrate the feasibility of fabricating LSCs emitting in the NIR region. In this work, NIR-emitting LSCs are reported using silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (SiNc or NIR775) immobilized in an organic-inorganic tri-ureasil matrix (t-U(5000)). The photophysical properties of the SiNc dye incorporated into the tri-ureasil host closely resembled those of SiNc in tetrahydrofuran solution (an absolute emission quantum yield of ∼0.17 and a fluorescence lifetime of ∼3.6 ns). The LSC coupled to a Si-based PV device revealed an optical conversion efficiency of ∼1.5%, which is among the largest values known in the literature for NIR-emitting LSCs. The LSCs were posteriorly coupled to a Si-based commercial PV cell, and the synergy between the t-U(5000) and SiNc molecules enabled an effective increase in the external quantum efficiency of PV cells, exceeding 20% in the SiNc absorption region.

Optical fiber relative humidity sensor based on a FBG with a di-ureasil coating.

In this work we proposed a relative humidity (RH) sensor based on a Bragg grating written in an optical fiber, associated with a coating of organo-silica hybrid material prepared by the sol-gel method. The organo-silica-based coating has a strong adhesion to the optical fiber and its expansion is reversibly affected by the change in the RH values (15.0-95.0%) of the surrounding environment, allowing an increased sensitivity (22.2 pm/%RH) and durability due to the presence of a siliceous-based inorganic component. The developed sensor was tested in a real structure health monitoring essay, in which the RH inside two concrete blocks with different porosity values was measured over 1 year. The results demonstrated the potential of the proposed optical sensor in the monitoring of civil engineering structures.