Abstract: A method of improving efficiency of solar cells made of crystalline silicon, including monocrystalline silicon, multicrystalline silicon and polycrystalline silicon is provided. In the method, a negative bias pulse is applied to solar cells at a predetermined voltage, a predetermined frequency, and a predetermined pulse width while immersing the solar cells in a hydrogen plasma. Hydrogen ions are attracted and quickly implanted into the solar cells. Thus, the passivation of crystal defects in the solar cells can be realized in a short period. Meanwhile, the properties of an antireflection layer cannot be damaged as proper operating parameters are used. Consequently, the serious resistance of the solar cells can be significantly reduced and the filling factor increases as a result. Further, the short-circuit current and the open-circuit voltage can be increased. Therefore, the efficiency can be enhanced.