Structural and Electronic Properties of Semiconductor‐Sensitized Solar‐Cell Interfaces

A recent study has reported a power‐conversion efficiency of 5.1% for solar cells employing mesoporous TiO₂ films sensitized with quantum dots of stibnite (Sb₂S₃). Here, a first‐principles atomic‐scale investigation of the interface between TiO₂ and Sb₂S₃ is presented. The proposed atomistic interface model is free of defects, and the calculated energy‐level alignment at the interface indicates that the ideal open‐circuit voltage is as high as 1.6 V. Films sensitized with the isostructural compounds bismuthinite (Bi₂S₃) and antimonselite (Sb₂Se₃), which exhibit band gaps closer to the ideal Shockley–Queisser value are also examined. In the case of Bi₂S₃ the calculations indicate that the lowest unoccupied molecular orbital is too low in energy to inject electrons into TiO₂, in agreement with experimental data. For antimonselite (Sb₂Se₃) the calculations predict a type‐II heterojunction with TiO₂, and suggest that Sb₂Se₃ sensitization may lead to higher power conversion efficiencies than found in the TiO₂/Sb₂S₃ system.