The difference between n-type and p-type solar cells

Wafer-types

First, a conventional crystalline silicon (c-Si) solar cell is a silicon wafer doped with various chemicals to encourage power production. The main difference between p-type and n-type solar cells is the number of electrons. A p-type cell usually dopes its silicon wafer with boron, which has one less electron than silicon (making the cell positively charged). An n-type cell is doped with phosphorus, which has one more electron than silicon (making the cell negatively charged).

Although the first solar cell invented by Bell Labs in 1954 was n-type, the p-type structure became more dominant due to demand for solar technologies in space. P-type cells proved to be more resistant to space radiation and degradation. Since so much research was thrown into space-related solar technology, it was only natural that p-type cell dominance trickled down to the residential solar market.

But more solar manufacturers are adopting n-type structures because of their additional benefits. For one, since n-type cells use phosphorus instead of boron, they are immune to boron-oxygen defects, which cause decreased efficiency and purity in p-type structures. N-type cells are in turn more efficient and are not affected by light-induced degradation (LID).

The International Technology Roadmap for Photovoltaic (ITRPV) predicts that the market share of p-type mono-c-Si will hold around 30% through 2028, while n-type mono-c-Si will increase to about 28% from barely 5% in 2017. This correlates to the industry demand for more high-efficiency modules, so solar buyers can expect more n-type designs entering the mainstream.

The R&D behind both cell types is strong. While n-type solar cells may be more efficient at a surface-level, outputs on both types can be similar. Some examples to compare:

This June, REC released its N-Peak panel, a 60-cell n-type mono-c-Si module with half-cut cells rated at 330 W. In April, LONGi reached a record with its 60-cell p-type PERC mono-c-Si module with half-cut cells rated at 360 W.

Last May, Trina Solar hit 24.13% efficiency with its n-type mono-c-Si solar cell. This May, JinkoSolar hit a record-breaking 23.95% efficiency with its p-type mono-c-Si solar cell.