The typical structural layout of photovoltaic devices. Transparent, conductive ITO is applied onto glass, and a hole transport layer of PEDOT:PSS (poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate)) on top of that. The photoactive layer is a blend of the electron acceptor and donor atoms (see Figure 2), and the cathode interlayer is a low work-function metal used to lower the work function of the electrode on top to accept electrons.