# What is a n-type doped solar cell?

I always thought a solar cell consists of two areas, a n-type and a p-type doped one. So what exactly is meant by n-type doped solar cells? Does it not have a p-type doped area? And how does it work then? How would I get the recombined p-n area that lies in between, then, or is it not crucial for the solar cell to work?

Furthermore, I always thought that the "majority charge carrier" is independently defined for the p and the n type area, not for the whole solar cell, how does one even establish a good conductivity with only 1 doping type?

• When the Fermi level is exactly in the middle of the bandgap, i.e. $E_F = 1/2(E_c-E_v)$ then you have an intrinsic semiconductor, meaning equal density of conduction band electrons $n_0$ and free valence band holes $p_0$, or usually written as $n_0 = p_0 = n_i,$ (i for intrinsic) As you dope the semiconductor (i.e. increase one type of carriers), the latter turns into an inequality, e.g. $n_0>n_i>p_0$ for n-doped. So n-doped simply means the majority of carriers are electrons and not holes. Aug 31, 2015 at 22:34
• But do i not dope n type as well as p type ? Like i said does a solar cell not consist of two different doped areas ? What is the sense of having far more electrons than "holes", shouldn't the conductivity be determined by the lower amount of charge carriers?
– user85397
Aug 31, 2015 at 22:39
• @Mareck can you provide a reference of where this n-type only solar cell comes from? In principle it is possible because electric field is not needed for photovoltaic action. Only a way of selecting the carrier types on extraction is needed. However, minority carriers (the holes in n-type materials) will have short lifetime so efficiency may not be great. Sep 1, 2015 at 7:23

In a typical semiconductor, there might be $10^{17}~\mathrm{cm^{-3}}$ majority carriers and $10^6~\mathrm{cm^{-3}}$ minority carriers. In n-type semiconductors, the majority carriers are Negatively charged electrons whereas in p-type semiconductors, the majority carriers are Positively charged holes.