A solar cell having an improved structure of rear surface includes a p-type doped region, a dense metal layer, a loose metal layer, at least one bus bar opening, and solderable material on or within the bus bar opening. The solderable material contacts with the dense aluminum layer. The improved structure in rear surface increases the light converting efficiency, and provides a good adhesion between copper ribbon and solar cell layer thereby providing cost advantages and reducing the complexity in manufacturing. A solar module and solar system composed of such solar cell are also disclosed.