Vol.:(0123456789) 1 3 Applied Physics A (2019) 125:859 https://doi.org/10.1007/s00339-019-3161-0 Surface modifcation of silicon solar cell using TiO 2 and Ta 2 O 5 : fabrication and characterization Raghavendra Sagar 1  · Asha Rao 2 Received: 5 July 2019 / Accepted: 15 November 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract We report the fabrication and characterization of surface modifed silicon solar cells with the deposition of amorphous tan- talum oxide (Ta 2 O 5 ) and crystalline titanium oxide (TiO 2 ) nanolayers of thickness 54.9 nm and 69.82 nm, respectively, as antirefection coating (ARC) using RF-sputtering technique. The thickness of the flms measured by variable angle spectro- scopic ellipsometry and scanning electron microscopy is in close agreement. The transmittance measurement as a function of wavelength of incident light showed that the thin-flms deposited have lowest efective refectance in the wavelength range of 380 nm–570 nm indicating reduced light refection and enhanced light trapping as observed from UV–Vis measurements. Illuminated current–voltage measurements showed an increase in the short circuit current density (J sc ) and an increase of 1.54% in the efciency of the antirefection-coated cells. Results of the External Quantum Efciency measurement as a function of wavelength for the solar cells with ARC is also presented in this paper. 1 Introduction Increasing the performance of the Silicon solar cells by modifying the p–n junction with hetero-structure and metal oxide semiconductor structure have been some of the routes, since years. [1–4]. The deposition of high quality Antirefec- tion coating (ARC) in the solar cells also plays a vital role in improving the efciency of the cells by increasing the light trapping within the cell and allowing more photons to inter- act with cell structure, thereby improving the conversion capability of the solar cell [5, 6]. High quality ARCs must be designed accurately on mono- and multicrystalline silicon solar cell surfaces to minimize the loss of optical absorption and also for the passivation of the surface dangling bonds acting as recombination centers [7, 8]. It is reported that the silicon without ARC would only transmit about 70% of IR and 50% of UV portions of the sunlight into the cell structure [9]. Although other factors such as recombination, poor contacts, etc., infuence the solar cell efciency, overall performance of an actual Si solar cell is limited by light trap- ping conditions [10]. ARCs are of great importance to get low solar cell refectance. To achieve lowest refection of a single wavelength of incident radiation, the ARC may con- sist of a single-layer antirefection, satisfying the conditions like (a) square root of the refractive indices of the materials constrained the coating equal to the refractive index of the ARC, and (b) thickness of ARC equal to one quarter of the wavelength [11]. Bare silicon has a high surface refection of over 30%. Hence, light trapping mechanism is essential for the enhancement of incident light absorption. This requirement can be fulflled by two mechanisms, namely, difraction or scattering—which can change the direction of incident pho- tons so that as much as photons can propagate at higher angles with prolonged path length within the cell and the other is, coupling of incident photons provided with the guided mode in the active region of solar cell with a con- fnement of light [12, 13]. In simple words, once the incident photons enter into the device their mean residing time in active region must be long enough and should be absorbed before escaping the device. The most widely used materials for antirefection coating in silicon solar cells are titanium dioxide (TiO 2 ), tantalum oxide (Ta 2 O 5 ), tin dioxide (SnO 2 ), zinc oxide (ZnO), silicon nitride (SiNx), and zinc sulfde (ZnS) [14–19]. Among them, * Asha Rao asharao76@gmail.com; drasharao_phy@sirmvit.edu 1 Department of Physics, Mangalore Institute of Technology and Engineering (MITE), Badaga Mijar, Moodbidri, Karnataka 574225, India 2 Department of Physics, Sir M Visvesvaraya Institute of Technology, Hunasamaranahalli, Yelahanka, Bengaluru, Karnataka 562157, India