my openpyxl use is too slow, am I reading rows incorrectly?

[Clunk_Head]

I'm using openpyxl to read 500,000 to 900,000 record excel files with 100 columns, give or take.
I have a function that I'm using to read a row:

def read_row(worksheet, row, cols):
    row_data = []
    for index in range(1, cols + 1): 
        row_data.append(worksheet.cell(row, column = index).value)
    return row_data

but it takes between .2 and .8 seconds to read and return each row.
This average of .5 seconds times 900,000 translates to 5 days processing time for a single pull.
Is there any way to speed up this function or to use a faster module for excel?

For this I'm not married to any concept except using python to read excel so I'm open to any constructive advice.

Thank you