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 TiO 2 films sensitized with quantum dots of stibnite (Sb 2 S 3 ). Here, a first‐principles atomic‐scale investigation of the interface between TiO 2 and Sb 2 S 3 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 (Bi 2 S 3 ) and antimonselite (Sb 2 Se 3 ), which exhibit band gaps closer to the ideal Shockley–Queisser value are also examined. In the case of Bi 2 S 3 the calculations indicate that the lowest unoccupied molecular orbital is too low in energy to inject electrons into TiO 2 , in agreement with experimental data. For antimonselite (Sb 2 Se 3 ) the calculations predict a type‐II heterojunction with TiO 2 , and suggest that Sb 2 Se 3 sensitization may lead to higher power conversion efficiencies than found in the TiO 2 /Sb 2 S 3 system.