Hybrid Solar Cells with Polymer and Inorganic Nanocrystals - Organic Solar Cells: Materials and Device Physics - page 250

Fig. 9.8 a TEM image of CdSe tetrapods. Scale bar, 50 nm. b Molecular structure of
PCPDTBT. c Structure of PCPDTBT-CdSe solar cell. d J-V characteristics measured under AM
1.5 irradiation. Reproduced with permission from Ref. [ 47 ]
9.3.3 Nanorod, Nanowire, and Nanotube Arrays
Compared to the bilayer devices, bulk heterojunction HSCs have much higher
conversion efficiencies. However, they are still limited by the inefficient charge
transport caused by the discontinuous percolation pathways as shown in
Fig. 9.10 a, b. Therefore, an ordered heterojunction which has direct charge
transport pathways is generally regarded as an ideal structure for HSCs, as shown
in Fig. 9.10 c[ 77 ].
The ordered heterojunction can be formed by infiltrating conjugated polymers
into the vertically aligned nanostructures of the inorganic nanocrystals, such as
nanorod, nanowire, and nanotube arrays that can be prepared by a variety of
physical or chemical methods including nanoimprint [ 41 , 78 ], low temperature
liquid phase deposition [ 79 ], template method [ 80 ], anodization [ 81 ], etching [ 82 ],
and so on.
Cadmium Chalcogenide nanorod and nanowire arrays have been extensively
studied for preparing high performance ordered heterojunction HSCs in the past
years. Kang et al. [ 83 ] first reported such a device with an admirable PCE of 1 %