Novel excitonic solar cells in phosphorene-TiO2 heterostructures with extraordinary charge separation efficiency

Constructing van der Waals heterostructures is an efficient approach to modulate the electronic structure, to advance the charge separation efficiency, and thus to optimize the optoelectronic property. Here, we theoretically investigated the phosphorene interfaced with TiO₂(110) surface (1L-BP/TiO₂) with a type-II band alignment, showing enhanced photoactivity. The 1L-BP/TiO₂ excitonic solar cell (XSC) based on the 1L-BP/TiO₂ exhibits large built-in potential and high power conversion efficiency (PCE), dozens of times higher than conventional solar cells, comparable to MoS₂/WS₂ XSC. The nonadiabatic molecular dynamics simulation shows the ultrafast electron transfer time of 6.1 fs, and slow electron–hole recombination of 0.58 ps, yielding >98% internal quantum efficiency for charge separation, further guaranteeing the practical PCE. Moreover, doping in phosphorene has a tunability on built-in potential, charge transfer, light absorbance, as well as electron dynamics, which greatly helps to optimize the optoelectronic efficiency of a XSC.