In the given question, we are asked to identify the device that converts light energy into electrical energy. Let`s dissect each option to determine the correct answer.

Option 1: Light-emitting diode (LED)

A light-emitting diode emits light when an electric current passes through it. It does not convert light energy into electrical energy, so this option is incorrect.

Option 2: Laser diode

A laser diode is a device that emits coherent light through the process of stimulated emission. It also does not convert light energy into electrical energy, making this option incorrect.

Option 3: Solar cell

A solar cell, also known as a photovoltaic cell, is specifically designed to convert light energy, such as sunlight, into electrical energy. Solar cells contain materials that create an electric current when exposed to light, making this the correct answer.

Option 4: Transistor

A transistor is a semiconductor device that amplifies or switches electronic signals and electrical power. It does not convert light energy into electrical energy, so this option is incorrect.

Therefore, the correct answer is option 3: Solar cell. It is the device that converts light energy into electrical energy.