State-of-the-art passivation strategies of c-Si for photovoltaic applications: A review

The carrier recombination is a major bottleneck in enhancing the power conversion efficiency of first-generation solar cells. As a remedy, passivation minimizes the recombination at the surface and bulk by either neutralizing the dangling bonds or creating a field-effect. The review describes the evolution of the different cell structures based on passivation and classifies the passivation schemes according to the mechanism. The two ways of passivating the crystalline Si are either by reducing the minority carrier concentration at the surface or decreasing the intermediate density of states. Field-effect passivation is achieved by creating an electric field at the surface of Si to repel the minority carriers. The paper compares the typical and emerging dielectric layers in terms of substrate compatibility, effectiveness, interface qualities, and carrier-selective emitters for contact passivation. The effective lifetime of solution-based chemical passivation is compared for various electrolytes. In addition to surface passivation, it describes the advanced hydrogen passivation for bulk defects, such as shielded-hydrogen passivation and laser passivation. Further, the recent developments in the passivation strategies for trending solar cell architectures are discussed from the perspective of challenges.