Ionic works on browser but not on device

I am new to ionic and when I try to export excel nothing is happening on my device but it works on my browser.

here is my code.

  scannedResult: any[] = [];
  excel: any;
  contentvisibility = 'show';
  displayedColumns = ['firstname', 'lastname', 'company', 'email'];

  base64result: any;
  mstorage: Storage | null = null;

  key = 'key_' + Date.now().toString();
  private fileTransfer: FileTransferObject;

  constructor(private barcodeScanner: BarcodeScanner,
    private toastr: ToastrService, private storage: Storage, private plt: Platform,
) {


    this.storage.create();

    this.storage.get('item').then((res) => {
      if (res) {
        this.scannedResult = res;
      }
    });
  }
  async ngOnInit() {



    await this.storage.create();
  }


  startScan() {
    this.barcodeScanner.scan().then(barcodeData => {
      console.log('Barcode data', barcodeData);

      this.scannedResult.push(JSON.parse(barcodeData.text));
      this.storage.set('item', this.scannedResult)
        .then(
          () => {
            this.toastr.success('Item Stored Success');
          },
          error => console.error('Error storing item', error)
        );

      return barcodeData;


    }).catch(err => {
      console.log('Error', err);
    });
  }




   async createExcel() {
    const ws = XLSX.utils.json_to_sheet(this.scannedResult);
      // eslint-disable-next-line
    const wb = { Sheets: { 'data': ws }, SheetNames: ['data'] };
    const buffer = XLSX.write(wb, {
      bookType: 'xlsx',
      type: 'array'
    });
    alert(buffer);

    const fileType = 'application/vnd.openxmlformats-officedocument.spreadsheetxml.sheet';
    const blob: Blob = new Blob([buffer], { type: fileType });

 this.base64result =  this.convertFile(blob);

    this.saveToPhone(this.base64result);


  }



   saveToPhone(buffer: any) {

//for mobile native save
    Filesystem.writeFile({
      path: "Visitor_file10.xlsx",
      data: buffer,
      directory: Directory.Documents,
    });

//for browser save
    const downloadLink = document.createElement('a');
    const fileName1 = 'sample.xlsx';

    downloadLink.href = this.linkSource;
    downloadLink.download = fileName1;
    downloadLink.click();

    const currentDate = new Date().toLocaleString().replace(/[,:\s\/]/g, '-');
    const name = `myFile-${currentDate}.xlsx`;
     console.log(name);


      const readFilePath =  () => {
        const contents =  Filesystem.readFile({
          path: name
        });

        console.log('data:', contents);
      };
      console.log('data:', readFilePath);


    console.log("this is sit");
    console.log('this is siaat');

  }

  // convertBlobtoBase64 = (blob: Blob) => new Promise((resolve, reject)=>{

  //   const reader = new FileReader();

  //   reader.onerror = reject;
  //   reader.onload = () => {
  //    resolve(reader.result);
  //   };
  //   reader.readAsDataURL(blob);

  // });
  convertFile(file : Blob) : Observable<string> {
    const result = new ReplaySubject<string>(1);
    const reader = new FileReader();
    reader.readAsBinaryString(file);
    reader.onload = (event) => result.next(btoa(event.target.result.toString()));
    return result;
  }

}