Despite being introduced a long time ago, the iPhone 6 and iPhone 6 Plus still stand out as premium smartphones widely favored in the current market.
However, during usage, the iPhone 6 is not immune to occasional issues, with the black screen problem being one that causes distress for many users.

1. iPhone 6 in DFU mode (Device Firmware Upgrade)
DFU mode - Device software upgrade. Learn about this mode that puts Apple devices in a state requiring software restoration, reloading the latest operating system. When restored in DFU mode, the iPhone 6 operates more smoothly, with fewer errors and a cleanup of unnecessary files, preventing situations where the iPhone 6 screen goes black. You can identify this issue when the iPhone 6 screen remains blank, but calls are still received, and notifications appear on an invisible screen.
To resolve this issue, connect the device that needs restoration to the computer using a cable. Install and connect iTunes on your laptop, power off the phone. Then, keep holding the buttons, even when the Apple logo appears, to enter Recovery mode. If iTunes displays a message that the iPhone needs an update, click to Update, and the computer will download new firmware for the device. If it takes more than 15 minutes, the device may prompt you to restore again.
2. Running too many applications on the iPhone 6
Leaving multiple apps running in the background after use can cause conflicts. The iPhone 6 black screen issue indicates the phone is overloaded. The quickest solution is to restart the phone.
To resolve this, press and hold the volume buttons simultaneously with the side button until the Apple logo appears on the screen.
3. iPhone 6 battery depleted
Incorrect charging or prolonged use of a low-quality charger can cause the iPhone 6 battery to deteriorate, losing its ability to charge. The black screen on the iPhone 6 serves as a notification that the device is constantly low on energy and unusable.
To remedy this situation, once the battery is depleted, there is no option but to procure a new one.
4. Hardware Glitch on iPhone 6
Instances of this black screen glitch on iPhone 6 are rare but not unheard of. It might be a manufacturing defect, only noticeable upon usage. If your device is still under warranty, take it to the Apple service center for a replacement. If the warranty has expired, it's advisable to visit the service center for a thorough diagnosis and necessary repairs.
Hoping that the information provided here guides you in resolving the issue of a malfunctioning screen on iPhone 6 effectively.