Each plan established under section 3309.81 of the Revised Code shall require the school employees retirement board, or the entity administering the plan pursuant to a contract with the board, to cause an individual account to be maintained for each member participating in the plan. A plan may include deposits to the defined contribution fund created under section 3309.60 of the Revised Code or additional deposits made under section 3309.47 of the Revised Code to the employees’ savings fund.