Toward High-Performance Polymer Solar Cells:  The Importance of Morphology Control

Abstract

Polymer solar cells have the potential to become a major electrical power generating tool in the 21st century. R&D endeavors are focusing on continuous roll-to-roll printing of polymeric or organic compounds from solutionslike newspaperssto produce flexible and lightweight devices at low cost. It is recognized, though, that besides the functional properties of the compounds the organization of structures on the nanometer levels forced and controlled mainly by the processing conditions appliedsdetermines the performance of state-of-theart polymer solar cells. In such devices the photoactive layer is composed of at least two functional materials that form nanoscale interpenetrating phases with specific functionalities, a so-called bulk heterojunction. In this perspective article, our current knowledge on the main factors determining the morphology formation and evolution is introduced, and gaps of our understanding on nanoscale structure-property relations in the field of highperformance polymer solar cells are addressed. Finally, promising routes toward formation of tailored morphologies are presented.

Block copolymer strategies for solar cell technology

“…67 Evidently, the aforementioned parameter of the mean pathway length of an excitonic state for any particular material determines to a great extent what the optimum composite blend might look like. 21 Most of the processing and structural parameters that have been mentioned above are essentially concerned with optimizing the morphology around this important parameter and that of charge transfer. 21,[68][69][70][71][72] Several of the more common organic chemical structures that have been used in BHJ devices by various researchers are shown in Figure 3.…”

“…OPVs, on the other hand, have higher exciton binding energies and, therefore, excitons must reach a material interface with a lowest unoccupied molecular orbital (LUMO) offset to produce separated electrons and holes. 21 The photovoltaic mechanism in organic devices has been discussed at length in the literature, 19,[22][23][24][25][26][27][28][29] therefore, here, we only briefly outline the process for readers new to the field. Figure 1 shows the individual steps involved in the dominant process that converts light into an electrical current: (i) the incoming photon excites an electron from the HOMO to the LUMO of the donor material to (ii) create an exciton, (iii) which traverses the donor material to a donor-acceptor interface where (iv) the excited electron separates from its bound hole onto the LUMO of the acceptor.…”

The properties of SIRT, TVM, and DART for 3D imaging of tubular domains in nanocomposite thin-films and sections

“…Our model approximates the structures of a large range of functional nanocomposites, such as a bulk heterojunction composed of P3HT nanowires in a PCBM matrix [6,41] or carbon nanotubes in a polymer matrix [42].The ingredients of the model system therefore consist of a polymer matrix (background) having a slab-geometry and rod-like nanofillers (object), as can be seen in Figs. 1 and S1.…”

Solution processable interface materials for nanoparticulate organic photovoltaic devices

“…[1][2][3] Moreover, the use of non-toxic solvents is essential for commercial production to ensure environmental and occupational health and safety compliance. 4,5 Aqueous nanoparticulate (NP) dispersions of polymer and fullerene materials fulfil both of these requirements.…”