Polymer/Nanocrystal Hybrid Solar Cells: Influence of Molecular Precursor Design on Film Nanomorphology, Charge Generation and Device Performance

Abstract

In this work, molecular tuning of metal xanthate precursors is shown to have a marked effect on the heterojunction morphology of hybrid poly(3-hexylthiophene-2,5-diyl) (P3HT)/CdS blends and, as a result, the photochemical processes and overall performance of in situ fabricated hybrid solar cells. A series of cadmium xanthate complexes is synthesized for use as in situ precursors to cadmium sulfide nanoparticles in hybrid P3HT/CdS solar cells. The formation of CdS domains is studied by simultaneous GIWAXS (grazing incidence wide-angle X-ray scattering) and GISAXS (grazing incidence small-angle X-ray scattering), revealing knowledge about crystal growth and the formation of different morphologies observed using TEM (transmission electron microscopy). These measurements show that there is a strong relationship between precursor structure and heterojunction nanomorphology. A combination of TAS (transient absorption spectroscopy) and photovoltaic device performance measurements is used to show the intricate balance required between charge photogeneration and percolated domains in order to effectively extract charges to maximize device power conversion efficiencies. This study presents a strong case for xanthate complexes as a useful route to designing optimal heterojunction morphologies for use in the emerging field of hybrid organic/inorganic solar cells, due to the fact that the nanomorphology can be tuned via careful design of these precursor materials.

Nickel sulfide thin films and nanocrystals synthesized from nickel xanthate precursors

“…The observed changes in film morphology may be derived from several factors such as the different primary crystallite sizes (28 nm for NiXa-C6, 22 nm for NiXa-C7), differences in crystallization behavior of the precursors during deposition of the precursor films or different precursor reactivities, which have important implications on nucleation and growth kinetics. Regarding this latter issue, MacLachlan et al [53] and Lewis et al [60] have already demonstrated that the morphology of metal sulfide nanocomposites can be efficiently tuned by the chemical structure of xanthate or dithiocarbamate complexes. Similar as in the work of Lewis et al, the observed differences in film morphology in this study might also originate from changes in precursor reactivity.…”

“…The attractive properties of metal xanthates, like their usually good stability (also in solution), relatively low decomposition temperature (below 200°C) and simplicity to tailor solubility and decomposition behavior by variation of their organic side chains, have ensured that they are widely employed in the preparation of various metal sulfide nanomaterials [35][36][37][38][39][51][52][53][54][55][56][57][58][59][60].…”

“…A variety of binary (Bi 2 S 3 [52,61], CdS [53], CuS [36], HgS [36], MnS [36], ZnS [36], PbS [60], PdS [35], SnS [59], NiS [35][36][37][38][39]), ternary (copper indium sulfide [51], copper antimony sulfide [54]) and quaternary (copper zinc tin sulfide [55]) metal sulfide nanomaterials have already been synthesized via a thermally induced decomposition of the metal xanthates, proceeding via the Chugaev elimination mechanism [36,51]. Far less explored is the conversion of metal xanthates to metal sulfides at room temperature by photochemically induced decomposition using UV irradiation [56,57] or direct chemical reaction with primary amines.…”

In Situ Synthesis of PbS Nanocrystals in Polymer Thin Films from Lead(II) Xanthate and Dithiocarbamate Complexes: Evidence for Size and Morphology Control

“…roll-toroll manufacturing. 16,17,30 To date, the only metal sulphides to have been synthesised by the decomposition of single source precursors in a polymer film are CdS, 4,5,32,33 , CuInS 2 , 29 ZnS, 34,35 Bi 2 S 3 , 36 and Sb 2 S 3 . 31 Despite an extensive family of single source precursor molecules used for chemical vapour deposition and nanoparticle synthesis, [37][38][39][40][41][42] relatively few have been investigated within a polymer matrix.…”

Thermally and mechanically stable β-cyclodextrin/cellulose acetate nanofibers synthesized using an environmentally benign procedure

“…This was due to the chemical surrounding of Ag NPs that was affected by the addition of the Fe NPs, which in turn resulted in change in shape, size, and electron density of the NPs [39]. The shift could also be attributed to the extended defects and the microstrains of the peak shapes and widths of the NPs since NPs with the diameter less 100 nm are known to have defects on their surface [40].…”