Emitter doping profiles optimization and correlation with metal contact of multi-crystalline silicon solar cells

A systematic investigation of Phosphorus Oxychloride (POCl3) based diffusion optimization for the formation of homogeneous emitters and correlation with metal contact in p-type multi-crystalline silicon (multi-Si) solar cell is presented. The deposition temperature (810, 804, 798, 792 and 786 °C) was varied to achieve different sheet resistance (85, 90, 95, 100, and 105 ohm/square) measured by four points probes. The correlation between emitter quality, metal contact resistance (Rc) and cell performance was investigated. The results showed that the sheet resistance is higher, phosphorus surface concentration (Cs) is lower and emitter saturation current density (Joe) is lower. The cell data showed that the higher Rsheet result in higher Voc and Isc due to better short wavelength response from the External Quantum Efficiency (EQE) measurement, but lower fill factor (FF) due to higher emitter sheet resistance and contact resistance with Ag paste. The optimal Rsheet for this type of Ag paste (Samsung SDI 8630A) in this test is 90 ohm/square with the highest cell efficiency of 18.325%.