On the c-Si surface passivation mechanism by the negative-charge-dielectric Al2O3

Abstract

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Passivation of all-angle black surfaces for silicon solar cells

“…First, the capacity to chemically remove dangling bonds, thus interface trap states; second, the concentration of fixed charged that induces an electric field which repels one sign of carriers from the surface and prevents them recombining. In alumina films, it is well known that a post deposition anneal activates the passivation quality by improving both the field effect and the chemical components of passivation [25]. To test this, alumina coated specimens underwent a post deposition anneal for 30 mins at 400°C in a N2 atmosphere (500 sccm).…”

Effect of low thermal budget annealing on surface passivation of silicon by ALD based aluminum oxide films

“…This trend is observed in all the samples. Therefore, optimized sintering time for the best passivation is 105 s. It is to be noted that in most of the publications, 1,[7][8][9][10]27 annealing is done for longer time durations (10-30 min) and there is hardly any publication for shorter t anl . Table 2 summarizes the measured minority carrier lifetime and corresponding estimated SRV values with films of different thicknesses.…”

“…The reduction of such losses is of prime importance for numerous photonic devices such as light emitting diodes, photo-detectors and photovoltaic cells. 1 The losses emanating from the two surfaces can be reduced by surface passivation and is an area to be addressed for making efficient next generation devices. In order to reduce the cost of silicon solar cells made on expensive wafers (high quality silicon), thinner substrates (to reduce the usage in terms of watt g À1 ) are required.…”

“…2 Passivation reduces surface recombination losses by two ways, i.e., chemical passivation (reduction of the density of electronic surface states) and field effect passivation (the presence of fixed charges in the dielectric layer over the silicon surface that reduces the carrier density underneath the interface of the two). 1,[7][8][9][10] A well passivated surface reduces the recombination of photo-generated carriers in the vicinity of the two surfaces and improves the cell performance parameters. [11][12][13][14] Thermally grown silicon oxide (SiO 2 ), silicon nitride (a-SiN x :H) and amorphous silicon (a-Si:H) are commonly used for surface passivation of c-Si solar cells.…”

“…There are several reports related to the surface passivation property of Al 2 O 3 films deposited using thermal ALD process. 1,[7][8][9] The measure of surface passivation is surface recombination velocity (SRV) which can be deduced from the measured minority carrier lifetime values. Although in some papers, low SRV is obtained in as-deposited Al 2 O 3 films, 28 however, high quality surface passivation is realized after post deposition annealing.…”