Effects of particle size of aluminum powder in silver/aluminum paste on n-type solar cells

Silver paste, which mainly consists of silver metal, glass frit, and organics, has been used for contacting n + emitter of conventional p-type solar cells, whereas aluminum-added silver paste (silver/aluminum paste) has been used for p + emitter of n-type solar cells. It has been reported that the addition of aluminum powder to the silver paste decreases contact resistance between the paste electrodes and the p + emitter with increasing content of the aluminum powder in the paste, and in addition, that the silver/aluminum paste creates large and deep metallic spikes underneath the paste, which has been considered to decrease the contact resistance. However, how particle size of the aluminum powder affects the contact resistance and the electrical characteristics of the n-type solar cells has not been clear yet. In this study, the effects of the particle size of aluminum powder in the silver/aluminum paste on the contact resistance and the electrical characteristics are investigated. Our study demonstrates that the particle size of the aluminum powder strongly affects the contact resistance and the electrical characteristics. The contact resistance decreases not only with increasing the content of the aluminum powder in the silver/aluminum paste, but also with increasing the particle size of the powder. In addition, the optimization of the particle size of the aluminum powder can effectively increase FF of the n-type solar cells, resulting in increasing efficiency of the cells.