What is the name of the semiconductor device that converts voltage into light?

The correct choice is the Light Emitting Diode (LED) because this semiconductor device is specifically designed to emit light when an electric current passes through it. The process involves electroluminescence, where the energy released from electrons recombining with holes in the semiconductor material produces photons, which we see as visible light.

LEDs are widely used in various applications, including indicators, displays, and general lighting, due to their efficiency and longevity. Their ability to convert electrical energy directly into light without the substantial heat generation that incandescent bulbs produce further emphasizes their importance in modern lighting technologies.

In contrast, while a laser diode also emits light, it typically produces a coherent beam and is used in different applications such as lasers and optical devices. Photovoltaic cells convert light into electricity, functioning oppositely to how LEDs operate. Transistors serve as switches or amplifiers in electronic circuits but do not convert voltage into light.