Inclusion of nanometer-sized silicon crystallites in n-layer for open circuit voltage enhancement in amorphous silicon solar cell

• Mixed-phase Si:H n-layer with nanometer-sized Si crystallites (2–5 nm) embedded in a-Si:H matrix has been deposited.
• Significant Voc increase from approximately 50 mV to 100 mV can be obtained by incorporating the mixed-phase n-layer.
• Single-junction a-Si:H solar cell with high Voc of 0.945 V and initial efficiency of 9.4% was achieved.

Material properties of hydrogenated silicon n-layer and their impact on amorphous silicon (a-Si:H) solar cell are studied. By optimizing deposition parameters, mixed-phase n-layer with nanometer-sized Si crystallites embedded in a-Si:H matrix can be obtained, which demonstrates higher conductivity, lower activation energy and wider bandgap. Incorporating the mixed-phase n-layer into a-Si:H cell can significantly improve the open circuit voltage (Voc) up to 0.95 V, which is approximately 50 mV or 100 mV higher than those cells with a-Si:H n-layer or microcrystalline silicon n-layer, respectively. The possible explanations of Voc enhancement brought by the mixed-phase n-layer have also been discussed. Up to now, we have achieved an initial efficiency of 9.4% with high Voc of 0.945 V, FF of 0.70 and Jsc of 14.2 mA/cm2 with a-Si:H i-layer thickness of 300 nm and substrate temperature as high as 220 °C.