From ideas to implementation
The photoelectric effect

Contents
Introduction to the photoelectric effect: 2
The history of the photoelectric effect: 2
The effect of light on semiconductors in solar cells 3
Doping & Band structure: 3
The p-n junction 5
The photoelectric effect in photocells: 6
Applications of the photoelectric effect in photocells: 6
Current research: 8
Impact on society and the environment of solar cells: 8
Impact of advances in physics on scientific thinking & technology 9
Bibliography: 10

This report aims to gather and summarise information on the: use of the photoelectric effect in photocells
Effect of light on semiconductors in solar cells
Throughout this report a general understanding of semiconductors, solar cells, the photoelectric effect and photocells should be acquired. Current research on solar cells will be addressed as well as the underlying principles
Introduction to the photoelectric effect:
The photoelectric cell is also known as the phototube which is an electron tube in which electrons that are initiating an electric current originate by photoelectric emission. The photoelectric effect refers to the emission or ejection of electrons from the surface of a material (usually clean metal) when light hit it (electromagnetic radiation). It can now be experimented by zinc being exposed to ultraviolet light from burning magnesium, the charge leaked away pretty quickly. This method was found by Wilhelm hallwachs (1859-1894)

The history of the photoelectric effect:
Maxwell had predicted electromagnetic radiation, and Hertz confirmed that was electromagnetic radiation. Although these classical physicists like newton and Maxwell explained a lot their theories did not agree with the theory and the experiment of the black body radiation curves, hence was the birth of quantum physics. Quantum physics began in 1900 with max Planck, he proposed that radiation was emitted or absorbed in quanta ‘packets of energy”. From this the formula E=hf, where E is the energy of the photon, f is frequency and h is Planck’s constant 6.626 x 10^-34 J.s
Einstein extended the quantum theory to all forms of electromagnetic radiation. The core idea was Planck’s quantum theory but Einstein expanded this and predicted the results of the photoelectric effect. One of these was that different surfaces would have different graphs in relation to the frequency and maximum kinetic energy in the photoelectric effect. In 1916 Millikan succeeded in providing an experiment that showed his predictions to be true. These are Millikan’s results.
The effect of light on semiconductors in solar cells
Solar cells utilise the photoelectric effect to convert photons into electrical energy. They are photovoltaic devices with a semiconductor containing silicon (most commonly used material). In a semiconductor the gap between the valence and the conduction bands is smaller than that in an insulator. The photoelectric and photovoltaic are directly related but are different processes. The photovoltaic (PV) or solar cells converts photons to voltage, this is known as the PV effect. A PV cell has an electric field, this collects the freed electrons and gives them a direction, therefore the flow of electrons is a current. If this current is caught between metal contacts on the top and bottom of the cell, the current can be drawn upon and used externally. Solar cells do not need a potential difference in order for them to produce a current. ( Robert Emery, Catholic Schools Diocese of Maitland-Newcastle)

Doping & Band structure:
All band structure calculation techniques involve approximations which increase some aspects of the electronic properties in semiconductors while, at the same time, decreasing other aspects. Therefore, our purpose in studying the different computational methods is to understand their advantages and limitations. In so doing we will gain insight into the many different facets of electronic properties in semiconductors.