Positive muons can be used as local probes in solar cells to study the interface region between materials with n and p type conduction. Muons are implanted at different depths in the presence of an external magnetic field. The muon signal corresponds to the time evolution of the muon spin in the direction of the implantation beam . The signal amplitude decreases if the lattice around the muon stopping site suffers an increasing distortion, due to defects. Experimental results show that there is a defect region in the p material, near the interface, and the muon probe can be used to determine quantitatively which materials are more effective in reducing this region. This information is important for solar cells, since defects act as electron-hole recombination centres, reducing the device efficiency.
Paulo Brás, Paulo Silva, Jaime Silva