Abstract.Here, we report a new procedure for the co-sensitization with quantum dots (QDs) and dyes for sensitized solar cell. Cascade co-sensitization of TiO 2 electrodes are obtained by the sensitization with CdS quantum dots (QDs) and zinc phthalocyanines (ZnPcs), in which ZnPcs containing sulfur atom have been specially designed to produce a cascade injection by attaching directly to QDs. This strategy causes a double synergetic interaction. This is the differentiating point of cascade co-sensitization in comparison with other approach in which dyes with conventional functionalization are employed, that pursue anchoring dyes to TiO 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
I ntroductionAn elegant strategy to improve the light-harvesting in photovoltaic devices is to use complementary light harvesters capable to produce panchromatic absorption. Here we have combined semiconductor quantum dots (QDs) and ad hoc designed phthalocyanines (Pcs) in order to prepare sensitized solar cells with enhanced efficiency. QDs are among potential key players in the next generation of photovoltaic devices [1] due to their low-cost solution-phase processability, large absorption cross sections, a spectrally tunable absorption onset (achieved via the quantum size effect), and enhanced multiple exciton generation or carrier multiplication. [2] After the first report on a certified QD solar cell, [3] a remarkable progress has been reached just in a couple of years obtaining certified power conversion efficiencies (PCEs) approaching 9%. [4] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 3 On the other hand, Pcs are outstanding dye candidates in dye sensitized solar cells (DSSCs) due to their high extinction coefficient in the infrared spectral region and to their high thermal and chemical stabilities. [5] Pcs incorporated in DSSCs have achieved PCEs as high as 6.4 %, [6] still far away from the 12.75% PCE obtained by porphyrins, [7] their closest relatives. Light harvesting ability of QDs and Pcs can be enhanced by binding them, either covalent or supramolecular, producing a system capable to charge injection from both chromophores.However, the chemical combination of Pc rings to QDs has hardly been explored probably due to the difficulties to synthesize Pcs with the adequate anchoring groups. Until now just a few articles have been published where Pcs are covalently linked to QDs showing in most of the cases Förster resonance energy transfer (FRET) from QDs to Pcs. SiPc has been connected to CdSe QDs through axial ligation, [8] and also tetraminoZnPc [9] and unsymmetrically tris-tert-butyl-imidoZnPc [10] have been li...