Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 39: Photovoltaics II

HL 39.5: Talk

Wednesday, March 24, 2010, 10:45–11:00, H3

Interface recombination in heterojunction solar cells: influence of buffer layer thickness and interface charge — •Helena Wilhelm, Roland Scheer, and Hans-Werner Schock — Helmholtz Zentrum Berlin für Materialien und Energie, 14109 Berlin

In window/buffer/absorber type heterojunction solar cells the buffer/absorber interface is a very sensitive part. Due to the lattice mismatch there may be a high density of defects that can lead to a dominant recombination at the buffer/absorber interface. The recombination current depends on the carrier densities and thus on doping ratios, buffer layer thickness and interface charge.

The recombination current is characterized by two parameters - the diode quality factor and activation energy of saturation current density. These two parameters help to determine the recombination process and its location and can be extracted from the data of the temperature dependent current/voltage measurements.

The goal of this work was to investigate the influence of the buffer layer thickness and the interface charge on the diode quality factor and activation energy in cells with inverted buffer/absorber interface and to develop appropriate analytical expressions that include this influence. The analytical equations are verified by numerical device simulation. They describe that the diode quality factor largely depends on the buffer layer thickness and only to a minor extent on the interface charge.