Enroute Controller described event when weather information was apparently not issued to an air carrier who was struck by lightning; had smoke in the cabin and windshield spider web issues; the flight crew returned to the departure airport in an emergency status; reporter claimed position should have had d-side prior to the event.

Narrative

Moderate to extreme precipitation was in the bulk of my airspace. A long line of thunderstorms were in the area since I came in at XA00 local. The low altitude sectors were all combined. I did not have a D-side. I was working the sector alone with multiple aircraft; moderately busy; and lots of weather. ACR X was a departure out of ZZZ. I gave him direct XXXXX to keep him south of the thunderstorm line. I was calling weather to all other aircraft and was surprised that I did not call the weather to him until after his problem. At XI12 ACR X told me that he needed to return to his departure airport. AT XI17 ACR X told me that he was struck by lightning or something and that his windshield was a spider web. He said that there was smoke in the cabin and that they needed a fire truck standing by; I processed ACR X as an emergency. My Supervisor and Approach we notified of ACR X's problems and need for a fire truck. At XI31; I switched ACR X to Approach. All in all; the sector became extremely busy and should have been split out with all the weather in the area. I did not have a D-side until I told the Supervisor of ACR X's problem. I can only talk to one airplane at a time; and when you have 5 VHF frequencies and their VHF the sector gets congested fast. In hindsight; the sector should have been split before this ever happened.