Layer Effects of Photovoltaic Heterojunction of Fully Conjugated Heterocyclic Aromatic Rigid-rod Polymer Poly-$p$-phenylenebenzobisoxazole

Poly-$p$-phenylenebenzobisoxazole (PBO) contains fully conjugated rod like backbone entailing excellent optoelectronic properties$^{ }$and superior stabilities. Polystyrenesulfonate:poly (2,3-\textit{di}hydrothieno-1,4-\textit{di}oxin) (PEDOT:PSS) is a hole transferring medium which could be spun into a thin-film between indium-tin-oxide (ITO) and PBO to exhibit highly sensitive photovoltaic (PV) effect. PEDOT:PSS and PBO formed a donor-acceptor interlayer and made photoinduced charge transfer. Optimal absorption PV cell thickness for PBO was about 71 nm. By using a layer of lithium fluoride (LiF) as an electron transferring layer, the most open circuit voltage (V$_{oc})_{ }$and short circuit current (I$_{sc})$ were achieved at a LiF thickness of 1 nm. The V$_{oc}$ increased from 0.7 V to 0.9 V and the I$_{sc}$ increased one and half times.