I will discuss the computational tools we recently developed for treating coupled electron-ion dynamics based on time-dependent density functional theory, with which we explore the mechanisms for ultrafast electron-hole separation and recombination at the molecule/semiconductor interface.The resulting timescale and other features agree well with experiments.I will also discuss our recent efforts trying to establish structure-property relationship in dye solar cells, where we find the characteristic Ti-N interface bonds lead to beneficial effects such as increased open voltage and photocurrents.This motivated experimental efforts to adjust dye adsorption configuration at the organic/inorganic interface in the hope to improve energy conversion efficiencies.