F. Villar

Comparison of (n+) a-Si:H /(p) c-Si Heterojunction Emitters using a-Si:H Films Deposited by PECVD or HWCVD

In this work, we report on the last investigations of (n+) a-Si:H / (p) c-Si heterojunction solar cells deposited by both HWCVD and PECVD. Regarding HWCVD films, we use spectroscopic ellipsometry measurements to characterize the material properties of the deposited films. Particularly, we study the effect of the (i) a-Si:H film on the (n+) a-Si:H film growth. As far as PECVD films are concerned, an optimum PH 3 flow is determined from the point of view of dark conductivity. Additionally, QSS-PC measurements are used to determine the improvement in the passivation quality of this film. Finally, HWCVD and PECVD HIT emitters are compared. A high quality in both emitters is deduced with implied Voc values exceeding 665 mV

Optical and Morphological Characterization of PTCDI-C13

The organic photovoltaic technology has developed much in the last few years thanks to the optimization of the solar cell geometry and, specially, to the research for new performing materials. Nevertheless, much work has still to be done in order to better know the real mechanisms regulating the function of such novel class of semiconductors. The study of thin-film micro-structure, and the influence of the deposition parameters on it, is an important issue in order to obtain best optical and electrical properties. Thermal evaporation in high-vacuum chambers is the more suitable deposition technique to obtain organic thin-films with well organize molecular structure. Deposition parameters such as the substrate temperature and deposition rate may have some important effect on the molecules ordering. In this paper the effects of substrate temperature on structural and optical properties have been studied for N,N ′-ditridecyl perylene diimide (PTCDI-C 13 ) thin-films. Four samples have been deposited at 30, 60, 90 and 120°C substrate temperature and their absorption has been investigated by photothermal deflection spectroscopy (PDS) and transmittance spectroscopy. Moreover, simulations of the transmittance spectra have been calculated in order to obtain the optical constants n and k . Finally atomic force microscopy (AFM) has been employed to analyze the superficial morphology of the thin-films.

Characterization of UV laser ablation for microprocessing of a-Si:H thin films

Hydrogenated amorphous silicon has been widely studied last years, both from the basic research and industrial points of view, due to the important set of potential applications that this material offers, ranging from Thin Films Transistors (TFTs) to solar cells technologies. In different fabrication steps of a-Si:H based devices, laser sources have been used as appropriate tools for cutting, crystallising, contacting, patterning, etc., and more recent research lines are undertaking the problem of a-Si:H selective laser ablation for different applications. The controlled ablation of photovoltaic materials with minimum debris and small heat affected zone with low processing costs, is one of the main difficulties for the successful implementation of laser micromachining as competitive technology in this field. This work presents a detailed study of a-Si:H laser ablation in the ns regime. Ablation curves are measured and fluence thresholds are determined. Additionally, and due to the improved performance in optolectronic properties associated to the nanocrystalline silicon (nc-Si:H), some samples of this material have been also studied.