Nanoemitter structures

For realization of a photovoltaic nanoemitter structure with an n-Si(lOO) absorber, a nanoporous oxide matrix is prepared using the oscillatory photocurrent described in Section 2.4.1. Sample emersion was at the increasing branch of the photocurrent where the pores are comparably large and the oxide coverage is smaller than in the other photocurrent phases (cf. Figures 2.54 and 2.55) to ensure that most nanopores provide contact between Si and the electrolyte, thus facilitating pore deepening. 

Photo- and dark corrosion, however, can also be employed to judiciously modify semiconductor surfaces. The method is rather empirical but allows the in situ formation of interphases and of interfacial films that protect the photoelectrode while simultaneously allowing for efficient charge transport across the films. Examples are p-InP solar cells (photovoltaic and photoelectro-catalytic) [18,22,72,73], n-CulnSe2 [19,74] and nanoemitter structures with n- and p-Si nanoemitter structures with n- and p-Si [75, 76]. Examples will be presented in section 5 below. 

Several devices presented here are based on the novel nanoemitter concept that allows realization of efficient solar energy conversion structures. The device architecture also demonstrates that arguments regarding costs and abundance of materials have to be considered carefully cost-limiting factors in terrestrial applications can be drastically reduced if only trace amounts of precious metals have to be incorporated into the structures. For the photovoltaic nanoemitter cell shown in Figures 2.82 and 2.89, for a distance of 5 gm between the emitters, the cost for a square kilometer would be negligible (about 2500). In addition, noble metal con-... 

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