A maybe (hopefully) simple question about the denotations of "anode" and "cathode". The below image is a schematic of a polymer solar cell (Source (WBM)). (The figure text is quoted as well for the sake of context).
My question is only about the naming of electrodes. Isn't it correct that
- the cathode is the reducing electrode, which supplies electrons, while
- the anode is the oxidizing electrode, which accepts electrons?
Why would electrons (black spheres) move towards the negatively charged cathode, while positive holes (white spheres) move towards the positively charged electron-absorbing anode? Wouldn't the opposite make sense?
Is it a mistake on the drawing or should I re-think my understanding of the terms "anode" and "cathode"?
Figure 1. The working principle of the solar cell. Light enters the cell through the transparent anode, and is absorbed in the bulk heterojunction layer through generation of excitons (1). The excitons diffuse in the bulk heterojunction until they either recombine or reach a donor-acceptor interface, where they separate into electrons (black) and holes (white) (2). The electrons and holes will then move to the respective anode and cathode, through the donor and acceptor material phase (3).
If the figure is correct and I am the one being confused, then there are several other cases that seem to teach false. E.g. the following "PANIC"-remembering-rule to remember, which is cathode and which is anode (from this source, slide 8):
"*Negative is cathode", it says, and we are back to my question in the top: why do the electrons (black spheres) move towards the negative cathode in that schematic?
Many more diagrams agreeing with this latter one are found from a simple google search.