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Low-cost fabrication of nanostructured AlInP for high-performance ARCs in III-V solar cells

pubblicazioni - Poster

Low-cost fabrication of nanostructured AlInP for high-performance ARCs in III-V solar cells

Viene presentato un metodo a basso costo che ha l’obbiettivo di aumentare le performance dei coating antiriflesso (ARC anti-reflection coatings) applicati alle celle solari basate sui composti III-V della tavola periodica sfruttando la nano strutturazione dello strato finestra di AlInP. La nano strutturazione dell’AlInP riduce il valore del suo indice di rifrazione effettivo abbassando la riflessione della luce. Lo scopo può essere raggiunto nano strutturando il materiale con un attacco chimico utilizzando come maschera nano strutture di ossido. La maschera di ossido è stata realizzata depositando un film nano strutturato di Ta2O5 direttamente sullo strato finestra di AlInP utilizzando la tecnica di evaporazione da fascio elettronico su substrato tiltato di un angolo definito (GLAD Glancing Angle Deposition).

We present a low-cost method to improve the performance of anti-reflection coatings (ARCs) in III-V solar cells, based on nanotextured AlInP window layer. Nanostructuration of AlInP surface would significantly reduce the effective refraction index of the AlInP layer, key issue to match the optical requirements for lowering reflection. It can be achieved by means of chemical etching using a mask of oxide nano-pillars (NPs). Such a mask was realised depositing Ta2O5 NPs directly onto AlInP by means of electron-beam evaporation in glancing angle deposition (GLAD) configuration.

The width of the oxide NPs and their density on the AlInP surface can be easily tuned by changing the tilt angle of the substrate, while interrupting the evaporation at an early stage allowed us to control the NPs height. Later, chemical etching of AlInP was performed by means of HCl solution. Ta2O5 NPs, insoluble in HCl, were removed by lift-off effect. An accurate control of NPs dimensions and density appeared to be essential for the complete removal of the same NPs and for a uniform AlInP nanostructuration.

SEM images revealed the nano-engineered surface and cross-sectional images showed a pyramid-shaped nanostructure. Through X-ray diffraction it was verified the etch time to leave AlInP nanostructured layer without completely remove it on InGaP surface. Nanostructured AlInP in top cells reduced the reflectivity in the wavelength range 350-700nm compared to conformal layer. The nanostructured AlInP is a promising solution for high-performance ARCs in III-V solar cells for concentrated photovoltaics.

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