Lanthanum-doped ZnO nanorods as electron transport layer in perovskite solar cell

• मुख्य लेखक: Zainal Abidin, Nurul Aliyah
• स्वरूप: थीसिस
• भाषा: अंग्रेज़ी; अंग्रेज़ी
• प्रकाशित: 2024
• ऑनलाइन पहुंच: http://eprints.utem.edu.my/id/eprint/28631/; https://plh.utem.edu.my/cgi-bin/koha/opac-detail.pl?biblionumber=124338

Conventional Electron Transport Layer (ETL) TiO2 (Titanium dioxide) has been widely used in Perovskite Solar Cells (PSCs) which have produced encouraging Power Conversion Efficiency (PCE), allowing the technology to be highly regarded and propitious. Nevertheless, the recent high demand for energy harvesters in wearable electronics, aerospace and building integration has led to the need for flexible solar cells. However, the conventional TiO2 ETL layer is less preferred, where a crystallization process at a temperature as high as 450 °C is required, which degrades the plastic substrate. Zinc Oxide nanorods (ZnO NRs) is yet simple and low-cost fabrication may lead the task as ETL, but still suffer from low PCE due to atomic defects vacancy. To delve into the issue, Lanthanum (La) dopant has been introduced as an additive to passivate or substitute the Zn2+ vacancies. Pure ZnO nanorods and La-doped ZnO nanorods with different growth time (3,5,7,9 hours) and concentration (1 mol%-4 mol%) were synthesized by hydrothermal method with 90 ℃ of annealing temperature. The influence of different growth time and La concentration as dopant in terms of structural, optical and electrical properties have been investigated. Scanning electron microspcopy (SEM) revealed that La-doped ZnO produced smooth and stable morphology with less pore of nanorods compared to pure ZnO. From Raman-spectroscopy, La-doped ZnO at 1 mol% produced the best peak intensity with fewer defect peak. X-ray diffraction (XRD) revealed that the size of the crystal structure reduced, ranging from 23.626 nm to 27.089 nm when introducing La into ZnO lattice. The optical measurement from ultraviolet visible spectrometer (UV-Vis) indicates an enhancement of absorption in La-doped ZnO with transmittance value lies between 18.03% to 79.7% and direct bandgap between 2.90 eV to 3.39 eV. According to IV-measurement, 1 mol% of La-doped ZnO at 9 hours of growth time produced the best conductivity with 5.46 S/m making it the ideal concentration and growth time of La doped into ZnO. Following this, 1 mol%-9 hours was chosen as the ETL for SCAPS-1D study by applying its bandgap and absorption coefficient parameters obtained from the experiment. CH3NH3PbI3 (methylammonium lead iodide) was used as the absorber layer, Cu2O (copper (I) oxide) as Hole Transport Layer (HTL), Indium Tin Oxide (ITO) and platinum as front and back contact. The investigation was determined by varying various parameters within each tuned layer including layer thickness, doping concentration, defect density, electron affinity, bulk density, operating temperature and metal work function. From the simulation, the fully optimized device structure, ITO/La-ZnO/CH3NH3SnI3/Cu2O/Pt attained a PCE of 30.70%, proving a drastic improvement over the initial PCE of 19.21% by 59.81%. Therefore, this study proposes a low-cost hydrothermal synthesis method with a low operating temperature, and emphasizes novel doping techniques for efficient, lead-free PSC.