The development and importance of the surface passivation for the crystalline silicon(c-Si)solar cells,and various passivation films and surface passivation technologies are introduced.The latest research progresses of the surface passivation for the crystalline silicon solar cells both at home and abroad are described,a variety of surface passivation schemes using diffe-rent materials,such as SiO2,SiNx,SiCx and Al2O3,and the application advantages and disadvantages of the stacks are discussed emphatically.Based on the discussion above,it is pointed out that the SiO2/SiNx stack passivation films will be the key research of the industrial production,while the Al2O3 and its stacks will become a research focus for the laboratory in the future.The good surface passivation is one of the effective methods to increase the conversion efficiency of the crystalline silicon solar cells,thus the surface passivation for the crystalline silicon solar cells still is the global research hot spot on the way forward.

Application background,development history and basic principles of the light-induced plating(LIP) technology for solar cells are reviewed.The impact of LIP technology on the performance of solar cells is discussed,with emphasis on the improvement effect of the front-surface electrode contact performance for solar cells.In addition,the results achieved by applying LIP technology to two kinds of high-efficiency solar cells,i.e.Al-BSF and laser fired contact(LFC) solar cells.When the contact resistance becomes the chief component in the series resistance,the LIP technology may reduce the series resistance and enhance the fill factor,and eventually improve the cell efficiency.LIP technology is especially proper for cells with high series resistance.Besides that,annealing conditions can be optimized with the help of LIP technology for higher efficiency.

Silicon nanowire arrays (SiNWAs) are fabricated on polished pyramids of textured Si using an aqueous chemical etching method. The silicon nanowires themselves or hybrid structures of nanowires and pyramids both show strong anti-reflectance abilities in the wavelength region of 300–1000 nm, and reflectances of 2.52% and less than 8% are achieved, respectively. A 12.45% SiNWAs-textured solar cell (SC) with a short circuit current of 34.82 mA/cm2 and open circuit voltage (Voc) of 594 mV was fabricated on 125 × 125 mm2 Si using a conventional process including metal grid printing. It is revealed that passivation is essential for hybrid structure textured SCs, and Voc can be enlarged by 28.6% from 420 V to 560 mV after the passivation layer is deposited. The loss mechanism of SiNWA SC was investigated in detail by systematic comparison of the basic parameters and external quantum efficiency (EQE)of samples with different fabrication processes. It is proved that surface passivation and fabrication of a metal grid are critical for high efficiency SiNWA SC, and the performance of SiNWA SC could be improved when fabricated on a substrate with an initial PN junction.

Firstly,the development of the aluminum oxide(Al2O3)passivation technology is reviewed,and the preparation methods are summarized.Then,the material properties and passivation mechanisms of the Al2O3 films are described in detail.It is pointed out that the Al2O3 films have excellent field-effect passivation property and chemical passivation property.Thus,the Al2O3 films can be well applied to the passivation of lowly doped and highly doped p-type silicon surfaces.Besides that,the Al2O3 films are of good heat stability,satisfying the requirement of screen-printed solar cells.Finally,the latest studies of the Al2O3 films passivation technology applied to crystalline silicon solar cells are presented,the application problems of Al2O3 films for the industry production are pointed out,and some effective solutions are proposed in the light of these problems.

In the case of N-type solar cells, the anti-reflection property, as one of the important factors to further improve the energy-conversion efficiency, has been optimized using a stacked Al2O3/SiNx layer. The effect of SiNx layer thickness on the surface reflection property was systematically studied in terms of both experimental and theoretical measurement. In the stacked Al2O3/SiNx layers, results demonstrated that the surface reflection property can be effectively optimized by adding a SiNx layer, leading to the improvement in the final photovoltaic characteristic of the N-type solar cells.