Export the write-output into the html rapport

Dear expert
Im trying to build a server rapport for uptime using the code below. In Powershell output, this code below work fine, now I want to convert the result into a html and show it there.
This is where I got my problem, it doesnt work as I want, I want it to show the write-output in the html file, anyone can help?
Thanks

function Get-SystemInfo 
{ 
$ServerNames = Get-Content c:\serverlistOP.txt
foreach($server in $ServerNames){
$system = Get-WmiObject win32_operatingsystem -ComputerName $server
$uptime = (Get-Date) - $system.ConvertToDateTime($system.LastBootUpTime)
Write-Output ("Server: " + $server)
Write-Output ("Last boot: " + $system.ConvertToDateTime($system.LastBootUpTime))
Write-Output ("Uptime: " + $uptime.Days + " Days " + $uptime.Hours + " Hours " + $uptime.Minutes + " Minutes") 
}}
Get-SystemInfo | convertto-html > C:\test\test.html

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