Conformity of multi-step diffusion optimization towards high efficiency industrial mono-PERC Si-solar cells

Industrial processes involved in the fabrication of high efficiency mono-PERC silicon solar cells are largely relying on the emitter diffusion control. In this study, a multi-step (3-step) diffusion control is reported where different time profiles of diffusion are shown to drastically improve the power conversion efficiency from 23.29 % to 23.54 % ( i.e. a 1 % increase). Most importantly, their internal quantum yield (IQE) is enhanced from ca. 80–95 % at UV photon energies, ensuring lower thermalization losses by the optimization. On the other hand, an improvement in the carrier life-time from 40 to 68 µs , and a reduction in the emitter saturation current density from 255.5 to 77.1 fA/cm 2 are remarkable features which reduce the rate of non-radiative Auger recombination in the n-type emitter of the cell. A better diffusion gradient obtained from emitter profile also refers to a better charge carrier transport favoring the longer effective lifetime, improved current-voltage characteristics and higher quantum yields. The impedance spectroscopy eventually reveals a faster charge transfer kinetics for certain diffusion recipe, which can be modelled in a semi-empirical way to predict a best suited diffusion time profile for the industrial mono-PERC solar cells. • A 3-step diffusion optimization in mono-PERC silicon solar cell reported with improved emitter quality and reduced losses. • Power conversion efficiency increased from 23.29 % to 23.54 %. • Internal Quantum Efficiency (IQE) improved from ∼80–95 % in the UV range, ensuring lower thermalization losses. • Carrier lifetime increased from 40 µs to 68 µs, indicating a reduced recombination. • Electrochemical measurement confirmed an optimized doping profiles and enhanced interfacial charge transfer kinetics.