Gerard Masmitja

Development of a control system for an Autonomous Underwater Vehicle

Work proposes the development of a control system for an autonomous underwater vehicle dedicated to the observation of the oceans. The vehicle, a hybrid between Autonomous Underwater Vehicles (AUVs) and Autonomous Surface Vehicles (ASV), moves on the surface of the sea and makes vertical immersions to obtain profiles of a water column, according to a pre-established plan. The displacement of the vehicle on the surface allows the navigation through GPS and telemetry communication by radio-modem. The vehicle is 2300mm long by 320mm wide. It weighs 85kg and reaches a maximum depth of 30m. A control system based on an embedded computer is designed and developed for this vehicle that allows a vehicles autonomous navigation. This control system has been divided into navigation, propulsion, safety and data acquisition subsystems.

V2Ox-based hole-selective contacts for c-Si interdigitated back-contacted solar cells

Over the last few years, transition metal oxide layers have been proposed as selective contacts both for electrons and holes and successfully applied to silicon solar cells. However, better published results need the use of both a thin and high quality intrinsic amorphous Si layer and TCO (Transparent Conductive Oxide) films. In this work, we explore the use of vanadium suboxide (V2Ox) capped with a thin Ni layer as a hole transport layer trying to avoid both the intrinsic amorphous silicon layer and the TCO contact layer. Obtained figures of merit for Ni/V2Ox/c-Si(n) test samples are saturation current densities of 175 fA cm−2 and specific contact resistance below 115 mΩ cm2 on 40 nm thick V2Ox layers. Finally, the Ni/V2Ox stack is used with an interdigitated back-contacted c-Si(n) solar cell architecture fully fabricated at low temperatures. An open circuit voltage, a short circuit current and a fill factor of 656 mV, 40.7 mA cm−2 and 74.0% are achieved, respectively, leading to a power conversion efficiency of 19.7%. These results confirm the high potential of Ni/V2Ox stacks as hole-selective contacts on crystalline silicon photovoltaics.

Cost-effective cleaning solutions based on H 2 O/NH 3 /H 2 O 2 mixtures for ALD Al 2 O 3 passivated IBC c-Si solar cells

In this work we study cost-effective cleaning solutions applied to interdigitated back-contacted solar cells (IBC), which are passivated by means of atomic layer deposited Al<inf>2</inf>O<inf>3</inf> films. The cleaning baths must guarantee very clean surfaces as well as relatively low etching Al<inf>2</inf>O<inf>3</inf> rates to avoid excessive undercutting at the edges of strip-like regions. We compare the standard high-cost cleaning procedure used in the microelectronic industry (RCA1/2) with simpler cleaning baths based on H<inf>2</inf>O/NH<inf>3</inf>/H<inf>2</inf>O<inf>2</inf> mixtures considering different temperatures. The best option is the RCA1/2 sequence yielding surface recombination velocities below 4 cm/s but with a total Al<inf>2</inf>O<inf>3</inf> etch around 500 nm after the cleaning stage. Nevertheless very simple and less aggressive cleaning baths performed at only 45 °C obtain a relatively good surface passivation quality, achieving S<inf>eff</inf> values of 20 ± 5 cm/s reducing the under etch to only 80 nm.

Interdigitated back contacted c-Si(p) solar cells with photovoltaic efficiencies beyond 22%

In this work we show a baseline fabrication process of interdigitated back contacted IBC c-Si(p) solar cells, which combines conventional diffusion oven stages to define base p+ and emitter n+/n++ regions at the back side, with outstanding front surface passivation using atomic layer deposited Al2O3 films over random pyramids surfaces. Cells include a selective phosphorous n++ emitter in order to improve contact resistance and simultaneously reduce recombination current density. Fabricated devices reach efficiencies up to 22.2% (AM1.5G 1 kW/m2, T=25°C). This value is so far the highest efficiency reported by any Spanish institution using silicon substrates. 3D simulations envisage efficiencies beyond 24% introducing little changes in the fabrication process.

Boron diffused emitters passivated with Al 2 O 3 films

In this work we study the fabrication and characterization of boron diffused emitters using FZ c-Si(n) substrates. Emitter surface was passivated with Al2O3(25 nm thick) layers deposited by thermal atomic layer deposition ALD technique. This study covers a broad emitter sheet resistance Rsh range from 20 to 250 Ω/sq using both polished and textured wafers. Emitter electrical quality was tested by means of lifetime measurements using quasi-stationary photoconductance QSS-PC method. Dark saturation emitter current densities Joes were extracted from lifetime measurements resulting in Joes values ranging from 10 to 150 fA/cm2 depending on Rsh. These results are in the-state-of-the-art in boron emitter passivation.