How solar fundamentally works: from photon to power point

Light is energy delivery

Sunlight arrives as photons - discrete packets of energy. When a photon strikes a silicon solar cell, it can transfer its energy to an electron in the silicon, knocking it loose from its atom. That's the entire energy conversion, right there: light energy has become the energy of a moving electron. Everything else in a solar system is about herding those electrons in a useful direction.

Silicon is used because its atomic structure sits in a sweet spot: photons in sunlight carry enough energy to free its electrons, and it's the second most abundant element in the Earth's crust.

The junction: why electrons flow one way

A loose electron on its own just wanders and recombines - no use. The trick is the p-n junction: the cell is made of two silicon layers, each deliberately 'doped' with trace elements so one layer has surplus electrons and the other has a deficit. Where they meet, a permanent electric field forms.

Freed electrons that reach this junction get swept firmly to one side. That one-way sweep is what turns random photon strikes into an organised flow - a current - out through the metal fingers on the cell's face, through your circuit, and back. A solar cell is essentially a light-powered electron pump with no moving parts, which is why panels last decades.

From cell to panel to array

One cell produces a small voltage, so panels wire dozens of cells in series to add voltages - a modern 475 W panel is a weatherproofed package of interconnected cells behind toughened glass. Panels are then wired into strings to reach the DC voltages inverters want, and strings form your array.

This series wiring explains a famous quirk: shade one cell and you throttle its whole string, like kinking one point in a hose - the reason shading analysis matters far more than brochure wattage, and why bypass diodes and optimisers exist.

The inverter's translation

Cells produce direct current; your home and the grid run on alternating current that reverses direction 50 times a second. The inverter performs the translation - switching the DC electronically into a clean AC waveform, synchronised precisely to the grid's rhythm - while constantly hunting the array's maximum power point as light and temperature shift.

One counterintuitive footnote: panels are tested at 25°C and lose efficiency as cells heat beyond it, so a mild sunny day can out-produce a scorcher. Australia's solar abundance is about our light, slightly in spite of our heat.

That's the full journey: photon frees electron, junction herds it, series wiring accumulates it, inverter translates it, and your kettle neither knows nor cares that its energy left the sun eight minutes ago. For how this becomes bills and savings, our companion article covers the system level.