Connecting the (quantum) dots: towards hybrid photovoltaic devices based on chalcogenide gels (original) (raw)

2012, Physical Chemistry Chemical Physics

CdSe(ZnS) core(shell) aerogels were prepared from the assembly of quantum dots into mesoporous colloidal networks. The sol-gel method produces inorganic particle interfaces with low resistance to electrical transport while maintaining quantum-confinement. The photoelectrochemical properties of aerogels and their composites with poly(3-hexylthiophene) are reported for the first time. Organic solar cells based on conjugated polymers are among the most promising devices for solar energy conversion. The "classical" device consists of a bulk-heterojunction of a polymer-fullerene network, using poly(3-hexylthiophene) (P3HT) and the soluble fullerene derivative [6,6]-phenyl C 61-butyric acid methyl ester (PC 61 BM). The introduction of small alkyl thiol molecules, optimization of solvent conditions, and use of conjugated copolymers with smaller band gaps along with PC 71 BM enabled significant improvements in the efficiency of these devices, reaching ~ 7 %. 1,2 However, bottlenecks such as morphology control, the mismatch with the solar spectrum and stability still persist. The easily tunable optical properties, high extinction coefficients, electron affinity and intrinsic dipole moments of inorganic semiconductor quantum dots (QDs), as well as their potential for multiple exciton generation makes QDs such as CdSe, 3,4 CuInSe 2 , 5 PbS, 6 and PbSe 7 promising alternatives to organic fullerene derivatives in hybrid solar cell devices. The addition of QDs in polymer solar cells should enhance the light-harvesting, thus offering the possibility of higher photocurrents. However, the highest efficiencies achieved for this kind of QD-based solar cells are still around 3 %, 8,9,10,11 mainly due to the poor charge transport properties of the inorganic phase, where transport occurs by hopping