Design and photovoltaic performance of nanorod solar cells with amorphous silicon absorber layer thickness of only 25 nm

We report on the design and photovoltaic performance of nanostructured three dimensional (nano-3D) solar cells with ultrathin amorphous hydrogenated silicon (a-Si:H) absorber layers. Zinc oxide (ZnO) nanorods are employed as the building blocks for the nano-3D solar cells. The ZnO nanorods with controlled morphology are prepared by aqueous solution deposition at 80°C. The nanorod a-Si:H solar cells are realized by depositing n-i-p a-Si:H layers over Ag-coated ZnO nanorods. The photovoltaic performance of the nano-3D solar cells is experimentally demonstrated. With an ultrathin absorber layer of only 25 nm, an efficiency of 3.6% and a short-circuit current density of 8.3 mA/cm2 are obtained, significantly higher than values achieved for the planar or even the textured counterparts with a three times thicker (~75 nm) a-Si:H absorber layer. By increasing the absorber layer thickness in the nano-3D solar cells from 25 nm to 75 nm, the efficiency improved from 3.6% to 4.1% and the short-circuit current density increased from 8.3 mA/cm2 to 13.3 mA/cm2. The orthogonalization of the light path and the carrier transport path plays an important role in these nano-3D devices.