Perovskite solar cells (PSCs) have emerged as one of the most promising photovoltaic technologies, achieving power conversion efficiencies (PCEs) exceeding 26%. Among the materials used in PSCs, nickel oxide (NiO_x) has become a key component for hole transport layers (HTLs) in p-i-n structured devices due to its chemical stability, suitable p-type characteristics, wide optical bandgap, and cost-effectiveness. These properties make NiO_x essential for efficient charge transport, reduced recombination losses, and enhanced device stability. Recent research has focused on improving the morphology, crystallinity, and photovoltaic performance of NiO_x thin films through advanced fabrication techniques such as sol-gel processing, chemical precipitation, sputtering, and pulsed laser deposition. Interface engineering strategies have also been explored to optimize energy band alignment and mitigate recombination at the NiO_x/perovskite interface. Despite these advancements, challenges such as scalability and long-term operational stability remain significant barriers to commercialization. This review critically examines recent progress in NiO_x-based HTLs, addressing both technical advancements and persistent challenges. By providing insights into the structural and photovoltaic properties of NiO_x, this study aims to support the development of scalable, high-performance PSCs and contribute to their integration as sustainable energy solutions.

Tin-lead (Sn-Pb) perovskite solar cells have garnered significant attention as a next-generation photovoltaic technology due to their ideal bandgap, reduced toxicity, and high efficiency. However, issues such as tin oxidation and interfacial defects between the perovskite and electron transport layers (ETLs) hinder their performance and stability. In this study, Sn-Pb perovskite quantum dots (QDs) were introduced as surface passivation layers to address these challenges. The QDs were applied onto the perovskite layer and subsequently treated with isopropanol (IPA) to control the layer thickness and remove surface ligands. This approach effectively optimized the interfacial structure, reduced defect density, and suppressed tin oxidation, leading to decreased leakage current and a notable increase in open-circuit voltage (V_oc). Characterization techniques, including UV-Vis spectroscopy, XRD, and SEM, confirmed that QD treatment did not alter the structural integrity or bandgap of the perovskite films. Dark current analysis revealed a reduction in J₀, and photovoltaic measurements demonstrated an improvement in power conversion efficiency (PCE) from 16.2% for the control device to 20.4% for the QD-treated device. These results underscore the effectiveness of QD-based surface passivation in enhancing both the efficiency and stability of Sn-Pb perovskite solar cells.

Perovskite/silicon tandem solar cells are a promising next-generation photovoltaic technology capable of surpassing the efficiency limits of single-junction silicon cells. By combining the complementary light absorption of perovskite and silicon, these tandem devices can achieve power conversion efficiencies (PCE) approaching 35%. Practical application, however, demands precise spectral control and accurate performance evaluation to overcome current matching and perovskite material challenges. This report introduces an integrated strategy to improve performance assessment through LED-based spectral tuning and advanced measurement methodologies.

In this study, we present a simple and cost-effective patterning process for perovskite thin films using photo-induced decomposition. Using methylammonium lead iodide (MAPbI₃) as a model material, we demonstrate that exposure to a halogen lamp light through a shadow mask selectively decomposes the exposed regions into MAI and PbI₂, while the masked regions remain intact. Subsequent immersion in isopropyl alcohol (IPA) selectively dissolves MAI, leaving behind PbI₂ as an insulating layer. The patterned MAPbI₃ films retained their original crystal structure and optical properties. This method was applied to fabricate MAPbI₃-based resistive switching device arrays, successfully demonstrating ON/OFF operations under applied voltages. By utilizing the perovskite film itself as a photoresist and IPA as a developer, this approach eliminates the need for conventional photolithography chemicals and equipment, enhancing its practicality and scalability. With further refinement, this technique has the potential to significantly advance the development of perovskite-based semiconductor devices.

The transition to Zero Energy Buildings (ZEB) is actively promoted as part of the carbon neutrality policy. Accordingly, Building-Integrated Photovoltaic (BIPV) systems, which can be directly applied to building exteriors, have been gaining. This study evaluates the power generation performance of lightweight color film modules under outdoor conditions. BIPV modules were installed in a south-facing curtain wall structure in Gyeongsan-si, south Korea. Bi-facial cells were half-cut using the NDC method, and 12 half-cells were connected using a multi-busbar interconnection method to form strings, with a film-to-film structure. The monitoring system collected DC and AC output data every minute to analyze cumulative power generation. Solar irradiance at 90° and 25° angles was measured to assess the correlation between irradiance and module output, and module and ambient temperatures were monitored to evaluate temperature-dependent power variations. As a result, the film modules maintained a performance ratio above 80% on clear days (cloud cover less than 2) throughout the measurement period, indicating stable power generation.

The production of clean hydrogen represents a significant challenge in the context of efforts to reduce carbon emissions and facilitate the transition to sustainable energy sources. Among these various methods, hydrogen production through Photoelectrochemical (PEC) water splitting is regarded as a promising technology, as it employs solar energy to decompose water and generate hydrogen in an environmentally friendly method. To optimize the efficiency of PEC water splitting, it is crucial to select and design photoelectrodes and catalysts that are central to the reaction. PEC water splitting is a process that converts solar energy into electrical energy, facilitating the electrochemical breakdown of water into oxygen (O₂) and hydrogen (H₂). The formation of heterostructures, the application of nanomaterials, and the use of photoelectrode coatings have all been shown to significantly improve charge separation and light absorption efficiency. Additionally, catalyst surface modifications and integration have been demonstrated to suppress charge recombination and promote water oxidation reactions, thereby enhancing the characteristics and performance of PEC water splitting. These findings suggest the potential for developing high-efficiency, stable PEC systems and provide a path forward for advancing clean hydrogen production.