Vol.:(0123456789) SN Applied Sciences (2020) 2:870 | https://doi.org/10.1007/s42452-020-2670-y Research Article Cost‑efective ZnO–Eu 3+ flms with efcient energy transfer between host and dopant Archana Singh 1  · Priyanka Arya 1  · Diksha Choudhary 1  · Surender Kumar 1  · A. K. Srivastava 1  · I. B. Singh 1 Received: 2 August 2019 / Accepted: 2 April 2020 / Published online: 10 April 2020 © Springer Nature Switzerland AG 2020 Abstract The present work focuses on the deposition of Europium (Eu 3+ ) incorporated zinc oxide (ZnO) flm by a cost efective chemical solution deposition method. ZnO flm with varying concentration of Eu 3+ ions (2, 3 and 4 atomic percent) were deposited and characterized using diferent techniques like X-ray difractogram (XRD), scanning electron microscopy. XRD studies revealed that highly c-axis oriented ZnO flms without showing any segregation of europium oxide were obtained at 650 °C. The optical properties were determined using UV–visible spectrophotometry and photoluminescence measurements. UB-visible spectroscopy revealed that Eu 3+ doping shifted optical band gap with increase in transparency of the flms. The Eu 3+ doped flm showed intense emission at 614 nm which was attributed to the defect emission from ZnO that gets trapped by Eu 3+ ions ultimately leading to 7 F 2 to 5 D 0 transition in Eu 3+ . Keywords Thin flms · Eu-doped zinc oxide · Sol–gel · XRD · Optical absorption · PL 1 Introduction ZnO, because of its direct wide band gap of 3.37 eV, a large exciton binding energy (60 meV) [1], superior chemical stability [2] and unique optical properties, has triggered a vast research area for both fundamental and techno- logical reasons [3–7]. Doping in ZnO with selective ele- ment as well as intrinsic lattice defects greatly infuence its electronic, optical and magnetic properties either in flm or powder form [8–13]. Doped ZnO flms have attracted much attention because of their wide applications such as photoactive material for short wavelength light emit- ting devices, piezoelectric transducers, optoelectronic devices and transparent conducting electrodes [14–17]. Under proper excitation conditions, ZnO exhibits two kinds of emissions, one is an ultraviolet (UV) near band edge emission at 380 nm and other is a visible deep level emission with a peak in range from 450–730 nm [18, 19]. By doping ZnO with luminescence centre such as trivalent rare earth elements it is possible to enlarge the palette of colors emitted by it and also to tune its emission proper- ties, which would be greatly benefcial for light emitting device applications such as plasma display panels, multi color emission in light emitting devices [20–23]. To achieve efcient luminescence of ZnO–RE 3+ enhance energy trans- fer from semiconductor host to RE 3+ is required, but due to large ionic radii diference between two and also charge mismatching results are often disappointing. ZnO based flms have been prepared by number of dif- ferent techniques like spray pyrolysis [24], electrodepo- sition [8], pulsed laser deposition [25], sputtering [26], sol–gel [11, 13, 27, 28] and metal organic chemical vapor deposition method [29]. Among them, sol–gel method has distinct potential advantage over the other due to its ability to control micro structure by sol gel chemistry, highly economical and its room temperature approach. By controlling parameters like solvent nature, precursor nature and concentration, preheating temperature and time, post annealing temperature it is possible to obtain good quality thin flms with good control over chemical * Archana Singh, archanas002@gmail.com | 1 Advanced Materials and Processes Research Institute, Bhopal, India.