I have a similar requirement, I need to get invoice information after invoice save from admin.
<br/>
I fulfil the requirement using the event observer. <br/>
> app/code/Anshu/Customization/etc/adminhtml/events.xml

    <?xml version="1.0"?>
    <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
        <event name="controller_action_postdispatch_sales_order_invoice_save">
            <observer name="observer_admin_invoice_save" instance="Anshu\Customization\Observer\AnshuInvoiceSave" />
        </event>
    </config>



> app/code/Anshu/Customization/Observer/AdminInvoiceSave.php

    <?php
    
    namespace Anshu\Customization\Observer;
    
    use Magento\Framework\Event\ObserverInterface;
    
    class AnshuInvoiceSave implements ObserverInterface 
    {
        /**
        * @var \Magento\Framework\Registry
        */
    
       protected $_registry;
        
        public function __construct(
            \Magento\Framework\Registry $registry
        )
        {
            $this->_registry = $registry;
        }
    
        public function execute(\Magento\Framework\Event\Observer $observer) 
        {
            $invoice = $this->getInvoiceObject();
            // My Customization
        }
        
        private function getInvoiceObject()
        {
            return $this->_registry->registry('current_invoice');
        }
    
    } 
    
Check if it is helpful to you. <br/>
Magento version was 2.2.1