Abstract
Abstract This work reports the fabrication and characterization of multifunctional, nanostructured passivation layers formed using a self-assembly process that provide both surface passivation and improved light trapping in crystalline silicon photovoltaic (PV) cells. Scalable block copolymer self-assembly and vapor phase infiltration processes are used to form arrays of aluminum oxide nanostructures (Al2O3) on crystalline silicon without substrate etching. The Al2O3 nanostructures are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and spectroscopic ellipsometry. Injection-level dependent photoconductance measurements are used to determine the effective carrier lifetime of the samples to confirm the nanostructures successfully passivate the Si surface. Finite element method simulations and reflectance measurement show that the nanostructures increase the internal rear reflectance of the PV cell by suppressing the parasitic optical losses in the metal contact. An optimized morphology of the structures is identified for their potential use in PV cells as multifunctional materials providing surface passivation, photon management, and carrier transport pathways.
Highlights
With silicon solar cell efficiency values approaching their theoretical limit, the elimination of remaining energy conversion losses becomes more challenging
One such example was implemented using blistering in aluminum oxide (Al2O3) passivation layers produced by atomic layer deposition (ALD) [19]; blistering occurs through the gaseous desorption in the Al2O3 layer upon thermal treatments above a critical temperature
We investigate the potential of the Al2O3 passivating nanostructures for photon management when applied to the rear side of a silicon solar cell
Summary
With silicon solar cell efficiency values approaching their theoretical limit, the elimination of remaining energy conversion losses becomes more challenging. Alternative approaches to forming passivated surfaces with nanoscale local contacts have been demonstrated, but these approaches typically rely on random processes that limit the ability to engineer their optical and electrical properties One such example was implemented using blistering in aluminum oxide (Al2O3) passivation layers produced by atomic layer deposition (ALD) [19]; blistering occurs through the gaseous desorption in the Al2O3 layer upon thermal treatments above a critical temperature. In order to achieve such high-density metal contacts without the need for high resolution lithography, here we utilize a combination of self-assembly, atomic layer deposition, and metal thermal evaporation to fabricate nanostructured metal–dielectric networks that function simultaneously as a metallic contact, a high-quality optical reflector, and a passivating surface These structures exhibit great potential for engineering carrier transport properties
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