Correlation between TCO/p and p/i heterojunction and effect of n/TCO heterojunction on a-Si:H solar cell performance

The influence of front TCO/p(a-Si:C:H) heterojunction in correlation with p(a-Si:C:H)/i(a-Si:H) heterojunction on TCO/p-i-n/TCO/metal a-Si:H solar cell performance is examined using the ASPIN computer simulator. The results indicate that defect states at both heterojunctions affect the potential barrier profile at the TCO/p heterojunction, and that their increase lowers the free hole concentration in the p-layer. However, defect states at the p/i interface change the potential distribution in the i-layer more strongly, and hence also photoelectric properties. At the improved TCO/metal back contact, the effect of n(a-Si:H)/TCO heterojunction on the electrical properties is also examined. The analysis of n(a-Si:H)/TCO structures shows that the best electrical properties can be achieved with ZnO, which enables the reduction of the n-layer thickness, resulting in further enhanced quantum efficiency and short-circuit current.