The electrical properties and hydrogen passivation effect in mono crystalline silicon solar cell with various pre-deposition times in doping process

The doping process in diffusion furnace consisting of pre-deposition and drive-in steps is essential to create p–n junction in crystalline silicon solar cell fabrication, and its optimization is necessary to obtain the high conversion efficiency. In this work, pre-deposition time was varied to study the electrical properties of solar cells and its effect on the hydrogen passivation with various phosphorous doping profiles. As a result, solar cell conversion efficiency of 17.8% with 7 min pre-deposition was achieved. Dopant (phosphorous) concentration in the emitter measured by SIMS indicated that the surface with shorter pre-deposition time had lower dopant concentration. High concentration of phosphorous on the surface appears to be the source for the electron consumed by the stored hydrogen in making the neutral H2 gas during firing. The formation of neutral hydrogen gas is thermodynamically and stochastically more favorable than the reaction between Si with dangling bond and H. This means that the passivation by the stored H during firing is strongly controlled by the dopant on the surface. This result obtained herein lays the foundations to understand the relationship between the doping profile of diverse dopant species and its passivation effect.

► Pre-deposition time in doping affects the hydrogen passivation.
► We achieved the solar cell conversion efficiency of 17.8% with 7 min pre-deposition.
► High concentration of P on surface is the source for electron consumed by stored H.
► Passivation by stored hydrogen during firing is controlled by dopant on the surface.