Antireflective downconversion ZnO:Er3+,Yb3+ thin film for Si solar cell applications

Abstract

Hexagonal wurtzite phased ZnO:Er3+/Yb3+ thin films with various Yb concentrations were deposited on Si(111) substrate by Aerosol Assisted Chemical Vapor Deposition process. Post-annealed films at 1000 °C in air atmosphere showed a crystallinity enhancement. Yb3+ (4F7/2 → 4F5/2) 1000 nm emission increased with the increase of Yb3+ concentration emanating from an Er-Yb energy transfer. The reflectance percentage of 12% was achieved in the [250–1000 nm] range, and the refractive index of 1.97 was obtained for 632 nm wavelength. These results suggest that the (3 mol. % Er, 9 mol. % Yb) codoped film is a highly efficient antireflective downconversion layer for enhancing Si solar cell efficiency.

Growth rate induced high efficient light trapping/photon conversion ZnO:Nd 3+ nanodisk shaped thin films deposited by AACVD process

“…In addition, it can be seen that the sample's mean grain size D determined by the Debye-Scherrer method from the (002) films are in a uniform state of stress with the tensile components parallel to c-axis [34], which is attributed to the larger ionic radius of Nd 3+ (0.108 nm) compared to the Zn 2+ ion (0.074 nm). This radius mismatching increases the lattice constants "a" and "c", implying a unit cell expansion in ZnO:Nd 3+ films [26]. Regarding the XRD patterns in Fig.3a, only "c" parameter M A N U S C R I P T…”

“…It is renowned that the deposition temperature is the key parameter for both incorporation of the dopant and deposition process of the films [26,30,31]. To study the deposition processes of Nd doped ZnO thin films, we have investigated the growth rate versus deposition temperature.…”

“…Moreover, these contaminations quench the rare earth luminescence and provide a non-radiative relaxation route via vibrational excitation [26,31]. To study their presence, the FTIR measurements of the as-deposited films were recorded.…”

“…Films were deposited on Si (111) substrates in a hot walled reactor using a liquid source AACVD process described elsewhere [26]. High-purity grade Zinc acetates dehydrate (C 4 H 6 O 4 Zn·2H 2 O) and neodymium (III) tris(2,2,6,6-tetramethyl-3,5-heptadionate) (STREM society) chemicals were dissolved in 460 ml methanol-40 ml butanol mixed solvent with fixed Nd/Zn=10 mol.% molar percentage and 0.05 M total concentration.…”

“…ZnO thin film is often used as efficient transparent electrode and ARC layers for Si solar cells applications [26][27][28]. It is worthy to note that the most reported materials exhibiting high downconversion emissions are in the form of powders, nanocrystals, nanoparticles, ceramics M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 5 and glasses.…”