Evolution in morphological, optical, and electronic properties of ZnO:Al thin films undergoing a laser annealing and etching process

• Published in: Solar energy materials and solar cells Vol. 125; pp. 223 - 232
• Main Authors: Charpentier, C., Boukhicha, R., Prod׳homme, P., Emeraud, T., Lerat, J.-F., Cabarrocas, P. Roca i, Johnson, E.V.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.06.2014; Elsevier
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electronic properties; Energy; Engineering Sciences; Equipments, installations and applications; Evolution; Exact sciences and technology; Excimer laser annealing; Laser beam annealing; Natural energy; Optical properties; Photoelectric conversion; Photovoltaic; Photovoltaic cells; Photovoltaic conversion; Raman spectroscopy; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Texturing; Thin films; Transparent conductive oxide; X-ray diffraction; Zinc oxide; X-ray diffraction; Photovoltaic; Transparent conductive oxide; Raman spectroscopy; Excimer laser annealing; Texturing; Atomic force microscopy; Conducting material; Heat treatment; Transport properties; Hall effect; Chemical etching; Texture; Thin film; Surface structure; Metal coating; Optical transmission; Optical properties; Hydrogenated material; Zinc oxide; Silicon; Raman spectrometry; Optical reflection; Scanning electron microscopy; Electronic properties; Annealing; Light scattering; Photovoltaic system; X ray diffraction; Optical trapping; Excimer; Amorphous hydrogenated material; Transparent material; Microcrystal; Room temperature
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2014.02.027

The use of a combined excimer (XeCl=308nm) laser annealing (ELA) and chemical etching process (dubbed the “LaText” process) to generate textured ZnO:Al thin films suitable for thin-film silicon photovoltaic applications has been previously shown, but the evolution of the material during the laser annealing and texturing steps has not been thoroughly examined. In this work, we examine in detail the evolution of the properties of room-temperature sputtered ZnO:Al thin films during such a process. We reveal (i) the bulk structural changes induced during laser annealing through X-ray diffraction measurements (XRD) and Raman spectroscopy, (ii) the dramatic changes in surface morphology and macroscopic electronic properties before and after each step of the LaText process, through Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Hall effect measurements, and (iii) the exceptional light scattering properties of these films in both air and in a cell configuration, as measured by optical transmission and reflection measurements. In all, we show that the electronic transport properties in the final state are acceptable for thin film PV applications, and the optical properties are exceptional and demonstrate great potential for light-trapping performance for both a-Si:H and µc-Si:H solar cells. •Generation of textured ZnO:Al films by using a combined excimer laser annealing and chemical etching process.•Structural changes induced during laser annealing through X-ray diffraction measurements and Raman spectroscopy.•Changes in surface morphology and macroscopic electronic properties before and after each step of the LaText process.•Exceptional light scattering properties of annealed films in both air and in a cell configuration.•Great potential for light-trapping performance for both a-Si:H and µc-Si:H solar cells.