Employing screen printing technology, aluminum is applied to the back side of the n-type silicon wafer to see the effect of the heat treatment parameters on the Voc of the solar cell, Heat treatment at $850^{circ}C$ produces the highest Voc among various heat treatment conditions. Heat treatment at the temperatures higher than $850^{circ}C$ results in lower Voc, which is due to the destruction of the Al-Si alloy emitter layer. The destruction of Al-Si layer observed to be caused by the vigorous movement of silicon atoms toward aluminum layer during the heat treatment.