The Nitty Gritty of Solar Cells
It’s scorching summer day, I’m sure you’re familiar. You open your window at 7 in the morning and there’s already heat radiating through the glass. You sit around and watch TV for a little as the light seeps and the sun rises, so you almost instantly scoot away from it. Later you go out to eat with your friends, but you didn’t put on your shoes before leaving so your feet burn as you walk out to your car. When you arrive at the restaurant of course all the tables inside are taken so you sit in the heat boiling in your own sweat and burning your un-sunscreened skin.
We’ve all been there, one day or another. The sun sucks. It makes our skin peel, it gives us sweat mustaches, and it hurts our eyes like crazy. But with great power comes great responsibility, as they say. The sun in the strongest source of energy we have available to us, striking the earth with 174,000,000,000,000,000 watts of energy (1.74 x 10¹⁷) at any given moment. Ha, you didn't even read all those zeros. And you and your family probably only uses 1,250 watts a day. So basically, the sun is giving us a LOT of free energy that we need to get a hold of.

One method of harnessing the beautiful sun is using photovoltaic cells, or more commonly know, solar cells (which are part of the larger solar panel). Here you’re going to get a run down of what these panels are made of, how they’re made, and what they do.
Material and Production
So, what material and substances do solar cells and panels use? Essentially, there are two layer of pure silicon and each layer has added phosphorus or boron to enhance some properties. The silicon is first made and then doped (mixed with phosphorus or boron). A few more things are added on and the solar panel is complete!
Silicon in 3 Steps
Silicon is made in a few steps and goes from a gravel or quartz form to pure silicon ingots.
The first step is purification. The gravel is taken and put in a carbon arc, which basically releases the oxogen and leaves carbon dioxide and silicon behind. A floating zone technique separates the silicon and its impurities (leftover 02 and CO2) by moving a rod of the impure silicon through heated zones and eventually leaving impurities on one side and silicon on another.

Next, this pure silicon is made into a single crystal. The Czochralski method is fancy word for this step, and basically you take a small amount of silicon, dip it into melted silicon, and rotate it until it forms a cylindrical shape. This is called a boule or ingot.
Finally, the boule is made into wafers. The ingots are sliced and polished to be about 5 millimeters thick and have diameters anywhere from an inch to 11 inches. These are typically rectangles or hexagons so they can be put together easily.
Phosphorus and Boron — Doping
Doping is a scientific way to say we’re injecting the silicon with another substance to give it better properties. And why does the silicon need to be better in the first place? Well, adding these two elements to the silicon amplifies existing properties in silicon. Phosphorus, which is negative, creates an excess of electrons in the silicon. Boron, which is positive, creates a deficiency of electrons in the silicon. Later, you’ll see why this is key.
To dope, the silicon is heated to 2570 degrees Fahrenheit (or 1,410 degrees Celsius) so it becomes porous. The substance burrows itself in the pores and depending on how long the materials are exposed to heat or exactly how hot it is changes the depth of these burrows. Once doped, the layer of silicon with phosphorus and boron are labelled the n-type layer and p-type layer, respectively.
Finishing Touches
An actual solar panel is put together rather simply after than. The n-type silicon is layered on top of the p-type layer, and then a bunch of these little squares or hexagons are arranged (the layer that looks like a bunch of blue sqaures). A cover of silicon rubber or butyryl plastic — just to be protective — goes over the cell on both sides (grey clear layers) and a reflective/anti-glare glass goes on just the top (blue clear layer). There’s then a backing and a frame added (topmost and bottommost layers). The electronic components, like wires connecting the panel to the battery, are just copper (the little black box on the right).

Functions
So now that I’ve probably bored you out of your mind with small details, you’re probably wondering why those are important, or you know, why they make solar panels work.
Use of N and P Type Layers
Alright I’ve said this before, but I will restate for more clarity. The n-type (phosphorus) silicon layer is negative and has an excess of electrons as demonstrated with the extra electron around the phosphorus (diagram below on left). The p-type (boron) silicon layer is positive and needs electrons as demonstrated with the hole around the boron (diagram below on right). I try to think, negative must mean mean so he could be a thief and that’s why he has extra electrons; if he is positive he must be nice so he must have given away he electrons, so he has no more. (And yes, I just gendered the silicon layers, ‘it’ is boring.)

Either way, there are too many electrons in the top layer and too few in the bottom layer. So in comes energy from the sun (1), photons, and these kick out the electrons from n-type layer (2) and the kicked out electron fills a spot in the electron-defficient bottom layer (3). The top layer steals back this electron (4), and as more photons kick out more electrons from the top layer, the process is repeated and gets a flow of electricity (5).

Are you wondering if it’s really that simple? Why yes, yes it is.
Electricity and Storage
So the flow of electrons gets going and with that the flow of electricity. These electrical currents go through copper wires mentioned before which capture the direct current (DC). An inverter turns this DC electricity into something more usable, alternating current electricity (AC) to be exact. It is then used directly or stored in batteries.
There’s Only One Problem…
That was a lie. There are actually quite a few problems with solar panels. But there is only one huge problem with the technical side of solar panels. They’re really incompetent.
Inefficiency
The Shockley–Queisser limit, aka the detailed balance limit, is a calculation fo the inefficiency of solar panels with one p-n junction (one overlap of the p and n type layers). Solar panel efficiency maxes out at about 33.7%, so say a solar panel works at 1,00) watts per meter, it would only actually convert 337 watts.
In short, the three causes are as follows: blackbody radiation, when a lot of the energy hitting the solar panel just becomes heat energy; recombination, when an electron fills the hole in the P-type layer but this does not get emitted as heat or a photon; and spectrum losses when not all photons get converted into an elctron flowing through the circuit.
Overview
First, here’s a system of equations to help you out with part one of this.
— (silicon + phosphorus) + (silicon + boron) = solar cell
— silicon + phosphorus = n-type
— silicon + boron =p-type
Second, a short story to represent part two.
— Photon approaches the door of N and P’s house. N-type has too many people crowding the doorway, so Photon kicks one of them out. This person moves into the living room with P-type, who was a bunch of extra spots open. But just as one person comes to the living room, another one leaves the living room and heads to the doorway. Another Photon approaches and the cycle begins again.
As for the inefficiency, I hope to go more in depth in a later article. Thanks for reading and learning a little bit about the more intricate details of solar cells while having some fun in the process!!
