Dresden 2014 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 37: Focus Session: Sustainable Photovoltaics with Earth Abundant Materials I

DS 37.4: Hauptvortrag

Donnerstag, 3. April 2014, 11:15–11:45, CHE 91

Nanowire device concepts for thin film photovoltaics — •Silke Christiansen — Helmholtz Zentrum für Materialien und Energie, Berlin — Max-Planck-Institute for the Science of Light, Erlangen

Aligned silicon nanowire (SiNW) arrays to aim for power conversation efficiencies >>15% are fabricated on multi-crystalline Si layers on glass substrates using reactive ion etching with prior lithographic patterning using densely packed polystyrene (PS) spheres. Diameter, length, density and shape of SiNWs can be controlled and tuned for highest absorptions (close to 90%). Cell concepts with SiNWs are realized: (i) a hybrid organic/inorganic cell using SiNWs as absorber and PEDOT:PSS as a hole conducting polymer; (ii) a semiconductor-insulator-semiconductor (SIS) cell with SiNWs as absorbers, oxide (few Å thick Al2O3 by atomic layer deposition-ALD) ) tunneling barriers for charge carrier separation and a transparent conductive oxide (TCO here: Al:ZnO, by ALD). Initial thin film solar cell prototypes reached open-circuit voltages of > 680 mV, short-circuit current densities of even > 35 mA/cm2 and efficiencies >13%. Advanced analytics to improve materials and cells are: (i) electron beam induced current (EBIC) to study charge carrier distributions; (ii) electron backscatter diffraction (EBSD) to study structural quality of the multi-crystalline Si layer; (iii) integrating sphere measurements to study optical properties and (iv) 4-point nano-probing to study electrical properties. Alternative electrodes such as graphene or silver nanowire webs are studied to even further improve the cells.