Thin macroporous silicon heterojunction solar cells

Abstract

We demonstrate the processing of a heterojunction solar cell from a purely macroporous silicon (MacPSi) absorber that is generated and separated from a monocrystalline n-type Cz silicon wafer by means of electrochemical etching. The etching procedure results in straight pores with a diameter of (4.7 � 0.2) ?m and a distance of 8.3 ?m. An intrinsic amorphous Si (a-Si)/p +-type a-Si/indium tin oxide (ITO) layer stack is on the front side and an intrinsic a-Si/n +-type a-Si/ITO layer stack is on the rear side. The pores are open when depositing the layers onto the 3.92 cm 2-sized cell. The conductive layers do not cause shunting through the pores. A silicon oxide layer passivates the pore walls. The energy-conversion efficiency of the (33 � 2) ?m thick cell is 7.2%. (� 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Use of kerf-less technologies for thin wafer production could significantly reduce the silicon material consumption per solar cell. The separation of thin macroporous silicon layers from crystalline silicon wafers is a promising candidate for thin wafer production. This Letter reports on the first successful demonstration of an only 33 ?m thick free-standing macroporous silicon solar cell. � 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.