Efficient electron/hole transport in inorganic/organic hybrid solar cells by lithium ion and molybdenum trioxide codoping

In this work, the energy level of acceptor TiO₂ was successfully tuned by lithium ions and MoO₃ (denoted as Li_XMoO ₃) codoping, and both the electron and hole transfer from donor to acceptor at the interface of inorganic-polymer bulk-heterojunction were enhanced. In detail, by investigating the primary dynamics of acceptor/donor photoactive bilayers, the competition between the hot electron transfer and the hot electron cooling are clearly revealed. And also the less energetic electron transfer and the hole transfer accompanied by geminate recombination of electron-hole pairs were successfully distinguished by the long time decays. Notably, the conclusive evidences from the femtosecond transient absorption spectroscopy have uncovered that after doping with Li_XMoO ₃, the conduction band and valence band energy levels of acceptor have been elevated by 0.42 and 0.31 eV, respectively, and thus both the hot electron and hole transfer lifetimes have been shortened. Consequently, a notable power conversion efficiency of 2.70% is achieved as compared to 1.76% of pure TiO₂/P3HT. This work demonstrates that Li_XMoO ₃ dopant can facilitate suitable energy level alignment to gain the higher efficiency in simplified device architectures, without the need for complicated structures.