It was proved that ligand exchange with a short acid molecule is beneficial to a better electric contact between nanocrystals in inorganic QD solar cells [13, 14]. In this work, the nanomorphology

of the hybrid is critical to the performance of solar cells. A dense contact interface and good interpenetration of the two phases will be expectably beneficial to the performance of inorganic hybrid solar cells. Thus, a comparison of hybrid films with and without MPA learn more treatment was given through SEM characterization in Figure  1c. Densely packed nanocrystal films with homogenous and pinhole-free surface over large areas were observed in both samples. Although there are a few cracks appearing after MPA treatment which is caused by the replacement of a long OA molecule chain, nanocrystal

aggregation composed of NTs and QDs is more clearly observed (Figure  1c(right)). The variation in surface morphology after surfactant exchange was also confirmed by AFM characterization in Figure  2. Figure 2 AFM height images of hybrid films with OA-capped hybrids (a) and after MPA treatment (b). The bottom images show the corresponding film surface height along the lines in the AFM images. As can be seen, the OA-capped hybrid nanoparticle thin films exhibit a homogeneous topology, while clusters and agglomerates can be found on the selleck chemical hybrid film after MPA treatment. The surface height along the Dipeptidyl peptidase line part of the AFM image was shown at the corresponding bottom. Mainly, tiny and uniform nanoclusters are observed on the OA-capped hybrid surface, while larger sized nanostructures are demonstrated after

MPA treatment, which means that aggregation of nanoparticles appears due to the removal of the long OA surfactant. Thus, ligand exchange correspondingly promotes a closer contact between the two phases from which charge transfer and transportation is benefited. In order to more clearly observe the hybrid morphology, TEM thin film samples were prepared by spin coating a diluted hybrid solution onto a fixed copper net. The characterization results are shown in Figure  3. Without MPA treatment (Figure  3a,b,c), the hybrid presents a homogenous connection among NTs and QDs although there are some accumulations due to a large solution concentration (Figure  3a). Self-assembly of nanocrystals can be observed, showing uniform gaps between the adjacent particles (Figure  3b). Especially, the small CdSe quantum dots are presently surrounding and filling the gap of branched CdTe tetrapods (Figure  3c). The obvious self-assembling is caused by the existence of surfactants such as OA or TOPO. In contrast, agglomeration and aggregation in a large scale are shown after the hybrid film was solvent-treated with MPA (Figure  3d). The nanoparticles are densely connected and packed, which makes it difficult to tell where the CdSe quantum dots are located (Figure  3e,f).