This review focusses on UV organic light-emitting diodes and organic solid-state lasers, and covers their recent development from organic chromophores and device configuration to practical applications.

The solar-to-electric conversion efficiency of mesoscopic solar cells is highly dependent on electron extraction under solar irradiation and determines the charge recombination processes within devices. Boosting charge transfer via building energy level alignment has been proved to be a promising method to enhance the output power of solar cells. In the current work, we present the successful fabrication of functional biomass-converted carbon quantum dots with graded energy levels by doping nitrogen or sulphur atoms from lotus root powder. When employed as light absorbers for mesoscopic solar cells, light harvesting and electron extraction can be markedly increased arising from the band alignment of graded carbon quantum dots, yielding maximal power conversion efficiencies of 0.158% and 0.208% for bi- and tri-cascaded photovoltaics, respectively. The primary results demonstrate that the employment of an energy-graded architecture is a promising strategy to optimize the device output. Following this line of thought, we further fabricate a co-sensitized device by integrating graded carbon quantum dots with N719 dyes to enhance the electron extraction capability. The final device yields an efficiency as high as 9.04%, showing the potential application of carbon quantum dots in high-performance solar cells.

High-performance ultraviolet organic light-emitting diodes are assembled using liquid-phase exfoliated MoS ₂ and its composites, MoS ₂ –UVO and MoS ₂ +PEDOT:PSS.

The air quality index (AQI), as an indicator to describe the degree of air pollution and its impact on health, plays an important role in improving the quality of the atmospheric environment. Accurate prediction of the AQI can effectively serve people’s lives, reduce pollution control costs and improve the quality of the environment. In this paper, we constructed a combined prediction model based on real hourly AQI data in Beijing. First, we used singular spectrum analysis (SSA) to decompose the AQI data into different sequences, such as trend, oscillation component and noise. Then, bidirectional long short-term memory (BiLSTM) was introduced to predict the decomposed AQI data, and a light gradient boosting machine (LightGBM) was used to integrate the predicted results. The experimental results show that the prediction effect of SSA-BiLSTM-LightGBM for the AQI data set is good on the test set. The root mean squared error (RMSE) reaches 0.6897, the mean absolute error (MAE) reaches 0.4718, the symmetric mean absolute percentage error (SMAPE) reaches 1.2712%, and the adjusted R² reaches 0.9995.

Reliability of nonvolatile resistive switching devices is the key point for practical applications of next-generation nonvolatile memories. Nowadays, nanostructured organic/inorganic heterojunction composites have gained wide attention due to their application potential in terms of large scalability and low-cost fabrication technique. In this study, the interaction between polyvinyl alcohol (PVA) and two-dimensional material molybdenum disulfide (MoS₂) with different mixing ratios was investigated. The result confirms that the optimal ratio of PVA:MoS₂ is 4:1, which presents an excellent resistive switching behavior. Moreover, we propose a resistive switching model of Ag/ZnO/PVA:MoS₂/ITO bilayer structure, which inserts the ZnO as the protective layer between the electrode and the composite film. Compared with the device without ZnO layer structure, the resistive switching performance of Ag/ZnO/PVA:MoS₂/ITO was improved greatly. Furthermore, a large resistive memory window up to 10⁴ was observed in the Ag/ZnO/PVA:MoS₂/ITO device, which enhanced at least three orders of magnitude more than the Ag/PVA:MoS₂/ITO device. The proposed nanostructured Ag/ZnO/PVA:MoS₂/ITO device has shown great application potential for the nonvolatile multilevel data storage memory.