Try this:
import java.io.FileOutputStream;
import org.apache.poi.xssf.streaming.*;
class CreateSXSSFUnicode {
 public static void main(String[] args) throws Exception {
  char st = '\u2713';
  String[] headers = new String[] {"Area", "MOB Target", "Area Result", "MOB > Area"};
  try (SXSSFWorkbook workbook = new SXSSFWorkbook(); 
       FileOutputStream fileout = new FileOutputStream("Excel.xlsx") ) {
   SXSSFSheet sheet = workbook.createSheet(); 
   SXSSFRow row;
   int rowNum = 0;
   row = sheet.createRow(rowNum++);
   for (int c = 0; c < headers.length; c++) {
    row.createCell(c).setCellValue(headers[c]);
   }
   row = sheet.createRow(rowNum++);
   int c = 0;
   row.createCell(c++).setCellValue("City");
   row.createCell(c++).setCellValue("85%");
   row.createCell(c++).setCellValue("80%");
   //row.createCell(c++).setCellValue(st); // does not work as st is a char
   row.createCell(c++).setCellValue(String.valueOf(st)); // this works
   workbook.write(fileout);
   workbook.dispose();
  }
 }
}
Result:
