We explore two strategies to improve the performance of hybrid solar cells fabricated using poly(3-hexylthiophene) (P3HT) and colloidal PbSe nanocrystals, which have reached a 1 sun power conversion efficiency of 2.9%. Using an atomic passivation strategy towards inorganic ligand-capped nanocrystals, the electron mobilities of PbSe quantum dot films are improved from 1.95 × 10−6 cm2 V−1 s−1 to 1.15 × 10−5 cm2 V−1 s−1. Employing ultrasmall PbSe nanocrystals allows us to adjust their bandgaps towards the type II heterojunction with P3HT, thus achieving efficient charge separation and transfer between the polymer/inorganic constituents. The device performance dropped to half after 10 days' storage, and the P3HT/PbSe interface was found to play a primary role in this efficiency degradation.
