Charging your device in airplane mode, i.e. disconnecting it from the mobile network, Wi-Fi and Bluetooth, will make your smartphone charge faster.
Not only does the phone charge faster in airplane mode, it also saves the energy it would consume to keep all the apps that use data connection active in the background (Facebook, WhatsApp and Instagram above all). By not working, they prevent the phone from 'wasting' valuable energy when charging.
In addition, radiation from smartphones left charging during sleeping hours can cause nightmares, prevent us from falling asleep easily and wake us up several times each night. The reason is an alteration in the self-regulation system of certain processes, such as our biological clock or circadian rhythms.