Exploring polymer/nanoparticle hybrid solar cells in tandem architecture

Tandem solar cells offer the possibility to significantly enhance solar cell performance through harvesting a broader part of the solar spectrum by using complementary absorbing materials. We report on tandem solar cells, with at least one polymer/nanoparticle hybrid layer as absorber material, in which the nanoparticles are prepared in situ by thermal decomposition of metal xanthates directly in the polymer matrix. In a first series, we investigated a hybrid-organic tandem solar cell, with a hybrid solar cell consisting of the silafluorene containing low band gap polymer PSiF-DBT and copper indium sulphide (CIS) nanoparticles as the bottom cell, and a low band gap polymer (PTB7)/fullerene derivative (PC61BM) organic solar cell as the top cell in order to study different recombination layers. Tandem devices with open circuit voltages nearly reaching the sum of the individual cells have been realised. The short circuit current is equal to the value of the hybrid single cell and a fill factor above 50% is obtained, leading to power conversion efficiencies of about 4.1%. Furthermore, the first results on hybrid-hybrid tandem solar cells consisting of two PSiF-DBT/CIS solar cells are presented. Although the preparation of these double hybrid devices is challenging because of the necessity of two thermal annealing steps, the resulting multilayer stack reveals smooth and homogeneous layers with sharp interfaces. The first working hybrid-hybrid tandem solar cells still exhibited 81% of the sum of the open circuit voltages of the single junction solar cells. © 2013 The Royal Society of Chemistry

Bismuth sulphide-polymer nanocomposites from a highly soluble bismuth xanthate precursor

Bismuth sulphide nanocrystal-polymer hybrid layers are of interest for various optoelectronic, thermoelectric or sensing applications. In this work, we present a ligand-free in situ route for the formation of Bi2S 3 nanorods directly within a polymer matrix. For this purpose, we introduce a novel bismuth xanthate (bismuth(iii) O-3,3-dimethylbutan-2-yl dithiocarbonate), which is highly soluble in non-polar organic solvents. The analysis of the crystal structure revealed that the prepared bismuth xanthate crystallises in the monoclinic space group C2/c and forms dimers. The bismuth xanthate can be converted into nanocrystalline Bi2S3 with an orthorhombic crystal structure via a thermally induced solid state reaction at moderate temperatures below 200°C. In combination with the high solubility in non-polar solvents this synthetic route for Bi2S 3 is of particular interest for the preparation of Bi 2S3-polymer nanocomposites as exemplarily investigated on Bi2S3-poly(methyl methacrylate) and Bi2S 3-poly(3-hexylthiophene-2,5-diyl) (P3HT) nanocomposite layers. Atomic force and transmission electron microscopy revealed that Bi2S 3 nanorods are dispersed in the polymer matrix. Photoluminescence experiments showed a quenching of the P3HT fluorescence with increasing Bi 2S3 content in the hybrid layer. © 2013 The Royal Society of Chemistry

18_2040Krivovichev.indd

ABSTRACT The crystal structures of the 1M and 2M polytypes of tyrolite have been solved from single-crystal X-ray diffraction data. The structure of tyrolite-1M [monoclinic, P2/c, a = 27.562(3