Innovative Approaches to the Manufacture of Tin Dioxide-Doped Titanium Dioxide for Efficient Perovskite-Based Solar Cells

Renowned for their excellent optoelectronic properties, halogenated perovskite materials are making unprecedented advances in the photovoltaics field. This emerging photovoltaic (PV) cell technology, which exploits many different materials and coating technologies, holds the promise of low-cost, lightweight and flexible solar power generation [1]. Composed of an absorber layer sandwiched between an electron transport layer (ETL) and a hole transport layer (HTL), the electron carrier is among the various factors influencing the performance of perovskite photovoltaics. Leading ETLs materials, such as titanium dioxide (TiO₂) and tin dioxide (SnO₂) have emerged as high-performance in perovskites solar devices [2]. However, to further enhance the performance of the ETL, we need further improvement in their electrical and optical properties. To achieve the required performance, TiO₂, and SnO₂ materials are generally doped. Another very promising material is SnO₂-doped TiO₂, but its use has yet to be optimized. In this study, we report the fabrication of thin films using PVD magnetron sputtering and pulsed laser deposition (PLD) techniques. We determined the optimal compositions for SnO₂-doped TiO₂ and TiO₂-doped SnO₂ and obtained efficient ETLs with a very good crystalline atomic arrangement. In the case of sputtering technique, the thin films were deposited on fluorine doped tin oxide (FTO) and silicon substrates with temperature ranging from 250 to 450°C in a reactive (Ar+O₂) mixture using pure titanium and tin targets. For PLD, depositions were carried out using targets of TiO₂ containing 5, 10, and 15% of SnO₂ at substrate temperature of 500°C on FTO and silicon using the third harmonic (λ = 355 nm) of Nd:YAG nanosecond laser. Thus, the effect of tin dopant and titanium dopant on the surface morphology, microstructural, optical, and electrical properties of these ETL thin films were systematically investigated by using various range of measurements such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Ultraviolet–visible-near infrared (UV–Vis–NIR) spectroscopy, Raman spectroscopy, Rutherford backscattering spectroscopy (RBS), Nuclear Reaction Analysis (NRA), Hall Effect and four points probe measurements. For PLD technique, it is observed that a 15% ratio of tin oxide is efficient for improving both, the optical and electrical properties of titanium oxide. In the case of the sputtering technique, it has been observed that, depending on the deposition conditions (temperature, oxygen flow rate), pure TiO₂exhibits a resistivity lower than 10 mΩ.cm with visible range transmittance that can be adjusted according to the oxygen flow rate. These performances have been further improved by doping TiO₂ with tin. Our study provides novel insights into the improving both the optical and electrical properties of two promising ETL materials (SnO₂ doped TiO₂ and TiO₂ doped SnO₂) using two reproducible fabrication methods suitable for industrial development.<br/><br/>References :<br/>[1]Goje, A.A., Ludin, N.A., Fahsyar, P.N.A., Syafiq, U., Chelvanathan, P., Syakirin, A.D.A.G., Teridi, M.A., Ibrahim, M.A., Su'ait, M.S., Sepeai, S. and Yasir, A.S.H.M., 2024. Review of flexible perovskite solar cells for indoor and outdoor applications. <i>Materials for Renewable and Sustainable Energy</i>, <i>13</i>(1), pp.155-179.<br/>[2]Koech, Richard K., Reisya Ichwani, Deborah Oyewole, Moses Kigozi, Daniel Amune, Dahiru M. Sanni, Sharafadeen Adeniji et al. "Tin oxide modified titanium dioxide as electron transport layer in formamidinium-rich perovskite solar cells." <i>Energies</i> 14, no. 23 (2021): 7870.