A numerical approach to optimize the performance of HTL-free carbon electrode-based perovskite solar cells using organic ETLs.

Carbon electrode-based perovskite solar cells (c-PSCs) without a hole transport layer (HTL) have obtained a significant interest owing to their cost-effective, stable, and simplified structure. However, their application is limited by low efficiency and the prevalence of high-temperature processed electron transport layer (ETL), e.g. TiO2, which also has poor optoelectronic properties, including low conductivity and mobility. In this study, a series of organic materials, namely PCBM ((Park et al., 2023; Park et al., 2023) [6,6]-phenyl-C61-butyric acid methyl ester, C72H14O2), Alq3 (Al(C9H6NO)3), BCP (2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline, C26H20N2), C60, ICBA (indene-C60 bisadduct, C78H16) and PEIE (poly (ethylenimine) ethoxylated, (C37H24O6N2)n) have been numerically analyzed in SCAPS-1D solar simulator to explore alternative potential ETL materials for HTL-free c-PSCs. The presented device has FTO/ETL/CH3NH3PbI3/carbon structure, and its performance is optimized based on significant design parameters. The highest achieved PCEs for PCBM, Alq3, BCP, C60, ICBA, and PEIE-based devices are 22.85%, 19.08%, 20.99%, 25.51%, 23.91%, and 22.53%, respectively. These PCEs are obtained for optimum absorber thickness for each case, with an acceptor concentration of 1.0 × 1017 cm-3 and defect density of 2.5 × 1013 cm-3. The C60-based cell has been found to outperform with device parameters as Voc of 1.29 V, Jsc of 23.76 mA/cm2, and FF of 82.67%. As the design lacks stability when only organic materials are employed, each of the presented devices have been analyzed by applying BiI3, LiF, and ZnO as protective layers with the performances not compromised. We believe that our obtained results will be of great interest in developing stable and efficient HTL-free c-PSCs.

Modeling and Simulations of 4H-SiC/6H-SiC/4H-SiC Single Quantum-Well Light Emitting Diode Using Diffusion Bonding Technique.

In the last decade, silicon carbide (SiC) has emerged as a potential material for high-frequency electronics and optoelectronics applications that may require elevated temperature processing. SiC exists in more than 200 different crystallographic forms, referred to as polytypes. Based on their remarkable physical and electrical characteristics, such as better thermal and electrical conductivities, 3C-SiC, 4H-SiC, and 6H-SiC are considered as the most distinguished polytypes of SiC. In this article, physical device simulation of a light-emitting diode (LED) based on the unique structural configuration of 4H-SiC and 6H-SiC layers has been performed which corresponds to a novel material joining technique, called diffusion welding/bonding. The proposed single quantum well (SQW) edge-emitting SiC-based LED has been simulated using a commercially available semiconductor device simulator, SILVACO TCAD. Moreover, by varying different design parameters, the current-voltage characteristics, luminous power, and power spectral density have been calculated. Our proposed LED device exhibited promising results in terms of luminous power efficiency and external quantum efficiency (EQE). The device numerically achieved a luminous efficiency of 25% and EQE of 16.43%, which is at par performance for a SQW LED. The resultant LED structure can be customized by choosing appropriate materials of varying bandgaps to extract the light emission spectrum in the desired wavelength range. It is anticipated that the physical fabrication of our proposed LED by direct bonding of SiC-SiC wafers will pave the way for the future development of efficient and cost-effective SiC-based LEDs.

Predictors for Proximal Caries in Permanent First Molars: A Multiple Regression Analysis.

AIM: The aim of this study was to determine the predictors of proximal decay in the permanent first molar. MATERIALS AND METHODS: A cross-sectional study was conducted at the Department of Oral Medicine, Dow Dental College, Dow University of Health Sciences. A total of 171 patients presenting with 227 first molars were included. Calibrated examiners performed a detailed history and examination using a specialized form. The form recorded caries predictors and assigned a caries risk category based on the presence of these predictors. The statistical analysis was performed using the SPSS for windows version 17. A descriptive analysis was used to calculate the mean and proportions. Backward regression was carried out to evaluate the predictor for caries on mesial and distal surfaces at p ≤ 0.05. RESULTS: The included 171 patients presented with a total of 227 decayed first molars and 412 decayed proximal surfaces. The mesial surface was found to be more affected by decay (0.92 ± 0.85). The caries risk profile explains 60%, and caries on the adjacent surface explains 90% of caries occurrence on the mesial surface. In the case of distal surfaces, the predictor which can cause caries significantly was caries risk only. The caries risk profile explains the 3% of caries occurrence on distal surfaces. CONCLUSION: Our study identified caries on the adjacent tooth surface and the caries risk profile as significant predictors of future caries risk for the mesial surface of permanent molars. CLINICAL SIGNIFICANCE: Predictors for mesial and distal surfaces of the permanent first molar may differ. Overall caries risk and status of adjacent teeth must be taken into account to predict future caries occurrence.