Optimization of the junction profile through control of the doping heat profile for silicon solar cell applications

Single- and multi-crystalline silicon (c-Si) photovoltaic (PV) devices are the most popular solar cells and have provided the highest energy conversion efficiencies. The doping profile of POCl₃ diffusion is crucial for silicon solar cells. To achieve the optimized junction depth, the doping temperature and time are varied. The process sequences are explained by variation of the diffusion coefficient and solubility with variations which have to prove to be achieve necessary. Hydrofluoric acid is used for the wet chemical etching process to avoid kinks in the active dead layer at the silicon surface during emitter formation and at high phosphorus concentrations. To control the phosphorus concentration on the surface, the etch time is also varied. The manipulated two-step doping heat profile with different doping temperatures and times increased the V_oc and fill factor, thereby increasing the conversion efficiency (η) of the cell. The experimental results were consistent with AFORS-HET simulation results. Additionally, the manipulated two-step doping heat profile is more favorable for obtaining improved passivation and uniformity. For the emitter doped with two-step heat profile, the performance of a single-crystalline solar cell was found to be V_oc = 629 mV, J_sc = 37.98 mA/cm², FF= 78.79%, and η = 18.84%. For a multi-crystalline silicon solar cell, these values were found to be V_oc = 634 mV, J_sc = 35.50 mA/cm², FF= 77.35%, and η = 17.90%.