Simple Approach to Hybrid Polymer/Porous Metal Oxide Solar Cells from Solution-Processed ZnO Nanocrystals

This work is devoted to the development of hybrid bulk heterojunction solar cells based on porous zinc oxide (ZnO) electrodes and poly(3-hexylthiophene) (P3HT), using simple synthesis procedures and deposition techniques. Starting from ZnO nanocrystals with well-controlled properties, porous ZnO electrodes of suitable porosity are deposited by spin-coating, varying the main experimental parameters such as composition of the initial ZnO formualtion and choice of the organic ligand. Significant charge transfer yields are observed in the corresponding solar cells, and the influence of processing conditions oil device performance is investigated using conventional techniques as well as transient photovoltage/photocurrent decay measurements. The temperature used to sinter the ZnO electrode is found to be specifically crucial to ensure efficient charge transport in the device while avoiding a loss in interfacial area through nanocrystal coalescence. Using 8 x 13 nm ZnO nanorods, the best device exhibits a power conversion efficiency of 0.35% under 100 mW.cm(-2) AM 1.5G simulated solar emission. This strategy, using processing in air with simple deposition techniques, competes with related approaches based on nanostructured ZnO processed using more complex procedures. Moreover, device performance and photophysics are found to be greatly influenced by the morphology of the starting ZnO nanocrystals, illustrating that fine control of the inorganic component call effectively tune the performance of hybrid bulk heterojunction solar cells.