Electronic devices based on organic thin-film transistors (OTFT) have the potential to supply the demand for portable and low-cost gadgets, mainly as sensors for in situ disease diagnosis and environment monitoring. For that reason, poly(3-hexylthiophene) (P3HT) as the active layer in the widely-used bottom-gate/bottom-contact OTFT structure was deposited over highly-doped silicon substrates covered with thermally-grown oxide to detect vapor-phase compounds. A ten-fold organochloride and ammonia sensitivity compared to bare sensors corroborated the application of this semiconducting polymer in sensors. Furthermore, P3HT TFTs presented approximately three-order higher normalized sensitivity than any chemical sensor addressed herein. The results demonstrate that while TFTs respond linearly at the lowest concentration values herein, chemical sensors present such an operating regime mostly above 2000 ppm. Simultaneous alteration of charge carrier mobility and threshold voltage is responsible for pushing the detection limit down to units of ppm of ammonia, as well as tens of ppm of alcohol or ketones. Nevertheless, P3HT transistors and chemical sensors could compose an electronic nose operated at room temperature for a wide range concentration evaluation (1–10,000 ppm) of gaseous analytes. Targeted analytes include not only biomarkers for diseases, such as uremia, cirrhosis, lung cancer and diabetes, but also gases for environment monitoring in food, cosmetic and microelectronics industries.

Organic thin-film transistors (OTFTs) are miniaturized devices based upon the electronic responses of organic semiconductors. In comparison to their conventional inorganic counterparts, organic semiconductors are cheaper, can undergo reversible doping processes and may have electronic properties chiefly modulated by molecular engineering approaches. More recently, OTFTs have been designed as gas sensor devices, displaying remarkable performance for the detection of important target analytes, such as ammonia, nitrogen dioxide, hydrogen sulfide and volatile organic compounds (VOCs). The present manuscript provides a comprehensive review on the working principle of OTFTs for gas sensing, with concise descriptions of devices’ architectures and parameter extraction based upon a constant charge carrier mobility model. Then, it moves on with methods of device fabrication and physicochemical descriptions of the main organic semiconductors recently applied to gas sensors (i.e., since 2015 but emphasizing even more recent results). Finally, it describes the achievements of OTFTs in the detection of important gas pollutants alongside an outlook toward the future of this exciting technology.

Photovoltaic (PV) systems face challenges in achieving maximum energy extraction due to the non-linear nature of their current versus voltage (IxV) characteristics, which are influenced by temperature and solar irradiation. These factors lead to variations in power generation. The situation becomes even more complex under partial shading conditions, causing distortion in the characteristic curve and creating discrepancies between local and global maximum power points. Achieving the highest output is crucial to enhancing energy efficiency in such systems. However, conventional maximum power point tracking (MPPT) techniques often struggle to locate the global maximum point required to extract the maximum power from the PV system. This study employs genetic algorithms (GAs) to address this issue. The system can efficiently search for the global maximum point using genetic algorithms, maximizing power extraction from the PV arrangements. The proposed approach is compared with the traditional Perturb and Observe (P&O) method through simulations, demonstrating its superior effectiveness in achieving optimal power generation.

In this contribution, the selectivity toward a diabetes biomarker was demonstrated by a non-specific impedance-metric chemical sensor array from blends of graphene oxide (GO)-based materials as a multivariate system for simultaneous aqueous and gaseous analyte investigation. The electrical impedance of bare graphene either oxidized or after reduction (RGO) displayed high specificity toward ammonia. The sensitivity of GO thin-film capacitance was 10.4 %/ppm of ammonia dissolved in ultrapure water, whereas RGO resistance featured 1.8 %/ppm to gaseous ammonia. However, composites with metal oxides, despite even providing a superior sensitivity to ammonia, completely alter the sign of sensor response to enable distinction of alcohols. Ceria and cyclodextrin allowed GO to operate in air at room temperature with improved stability and a faster response of approximately 60 s. These materials made for an increase in sensitivity to acetone of 11 and 3.2 times, respectively, compared to RGO. Therefore, GO-based composites, as well as the junction of electronic nose and tongue arrays were fundamental to enable the separation of acetone from alcohols and ammonia after principal component analysis.

Polymeric transistor degradation was investigated on bottom and top gate structures. Shelf-lifetime studies in both kinds of devices demonstrate an accelerated increase in effective charge carrier mobility, threshold voltage, and off current in modulus when poly(3-hexylthiophene) (P3HT) is exposed to atmospheric gases. Although P3HT is underneath PMMA dielectric and gold gate electrode films, electrical parameters degradation can be only delayed by 100 h. Therefore, only glass encapsulation of the active area is capable of effectively preventing current modulation decrease after exposure to atmospheric gases. Differently from their bottom-gate counterparts, capped top-gate TFTs clearly present negative threshold voltage and positive hysteresis. An interface with reduced deep traps concentration and electrical characterization influence on shallow traps filling are believed to play a significant role in these top-gate P3HT/PMMA transistors under operating conditions. Alternating gate voltage stress along 3000 cycles provides evidence of electrical sweep as a cause of performance degradation. Similarly, dc gate bias stress monitored for 127 min can impair current modulation and shifts threshold voltage depending on its sign. Finally, reversibility of both kinds of stress points that shallow traps are the major problem in these capped devices.

The global interest in environmental issues and sustainable energy has propelled extensive research in photovoltaic (PV) technologies. Brazil has emerged as one of the top ten solar energy producers and flexible PV suppliers in the world. In this context, organic photovoltaic cells (OPVs) have garnered attention due to their flexibility and ability to integrate into various surfaces, albeit facing challenges regarding lifespan and efficiency compared to silicon cells. This review examines the current state of research on OPVs and thin-film solar technologies, employing the systematic literature review methodology Proknow-C. The review includes an analysis of raw materials such as conductive polymers, fabrication processes including film deposition and encapsulation, and technological advancements that enhance the efficiency and stability of OPVs. Utilizing the Proknow-C methodology, a bibliographic portfolio was constructed to identify the current state of research in this field. Of 268 papers from major scientific databases, only 30 were deemed relevant to the theme, highlighting a significant research gap. This paper is a valuable resource for researchers, providing an updated overview and a foundation for future investigations in organic photovoltaics. The results emphasize the importance of materials such as conductive polymers and donor–acceptor molecules and the role of nanotechnology in advancing OPVs. Innovations in manufacturing techniques, such as inkjet and blade coating-based printing techniques, are shown to increase efficiency by providing precise control over film thickness and uniformity and reducing costs through lower material waste. Overall, this review highlights the necessity of further exploration and collaboration within the scientific community to address the challenges and propel advancements in organic photovoltaic cells. These advancements are crucial for transitioning to cleaner energy sources, reinforcing the ongoing significance of thin-film technologies in energy innovation.