cvs file is not saved in android

public static string WriteCSV()

{

string savePath = Application.persistentDataPath + "cvsFile.csv";

     string[] cvsDataFormatData = new string[BodyDataManager.Instance.bodyDataList.Count];

     int index = 0;

     foreach (BodyData bodyData in BodyDataManager.Instance.bodyDataList) 
            {
         string data = bodyData.date.ToString() + "," + bodyData.sys.ToString () + "," +               bodyData.dia.ToString () + "," + bodyData.weight;

         cvsDataFormatData [index] = data;
         index++;
     }
     File.WriteAllLines (savePath, cvsDataFormatData);

}

This does not save in android device though it works in editor windows version. please help me, what is wrong with this code.