Laser Doped Solar Cell on CZ P - type Silicon , IEEE 35 th PVSC

For many years, the selective emitter approach has been well-known to yield cell efficiencies well above those achieved by conventional screen-printed cells. A simple and effective way of forming a selective emitter can be achieved by laser doping to simultaneously pattern the dielectric with openings as narrow as 8 m, and create heavy doping beneath the metal contacts. In conjunction with laser doping, light-induced plating (LIP) is seen as an attractive approach for forming metal contacts on the laser-doped regions, without the need for aligning masks or other expensive, long laboratory processes. As laserdoping is gaining increasing interests in the PV industry, selection of the most appropriate laser and processing conditions is important to ensure high yields in a production environment. In this work, we have identified a suitable laser that enables good ohmic contacts for a wide range of laser scan speeds. Sheet resistances of laserdoped lines as low as 2 ohms/sq was achieved at a scan speeds of <1 m/s, while a sufficiently high doping (~20 ohms/sq) is still achievable at scan speeds up to 6 m/s. Optimization of the laser parameters in this work lead to a cell efficiency of 18.5% being achieved with the laserdoped selective emitter (LDSE) structure. The cell also has an excellent pseudo fill factor (pFF) of 82.3% and a local ideality factor n nearing unity. This indicates there is minimal laser-induced damage and junction recombination as a result of the laser doping process.