Sodium diffusion from flat glass substrates during annealing changes properties of refined flat glass. In the case of the development of CuInSe2 thin film solar cell, annealing at 550 deg C is necessary for the formation of suitable crystalline phases. Sodium diffusing from the soda-lime-silica glass substrate influences crystal growth & the main electrical parameters of the solar cell. Different possibilities in sodium ion migration control are presented, considering the influence of glass composition on sodium diffusion & its chemical potential as well as passivation of sodium-containing glasses by diffusion barriers. Experimental results show that sodium-free substrates or glass compositions which immobilise sodium at tetrahedral sites of boron oxide or alumina can be used without further surface treatment.
