Design, fabrication and charge recombination analysis of an interdigitated heterojunction nanomorphology in P3HT/PC(70)BM solar cells

Recent Advances in Morphology Optimization for Organic Photovoltaics

Organic photovoltaics are an important part of a next-generation energy-harvesting technology that uses a practically infinite pollutant-free energy source. They have the advantages of light weight, solution processability, cheap materials, low production cost, and deformability. However, to date, the moderate photovoltaic efficiencies and poor stabilities of organic photovoltaics impede their use as replacements for inorganic photovoltaics. Recent developments in bulk-heterojunction organic photovoltaics mean that they have almost reached the lower efficiency limit for feasible commercialization. In this review article, the recent understanding of the ideal bulk-heterojunction morphology of the photoactive layer for efficient exciton dissociation and charge transport is described, and recent attempts as well as early-stage trials to realize this ideal morphology are discussed systematically from a morphological viewpoint. The various approaches to optimizing morphologies consisting of an interpenetrating bicontinuous network with appropriate domain sizes and mixed regions are categorized, and in each category, the recent trends in the morphology control on the multilength scale are highlighted and discussed in detail. This review article concludes by identifying the remaining challenges for the control of active layer morphologies and by providing perspectives toward real application and commercialization of organic photovoltaics.

Oleylamine-functionalized graphene oxide as an electron block layer towards high-performance and photostable fullerene-free polymer solar cells

Oleylamine-functionalized graphene oxide (GO) has a shallower energy level of conduction band (E_CB) and a deeper energy level of the valence band (E_VB) as compared to common hole extraction layer (HEL) materials, which make the electron block layer (EBL). Photoluminescence, X-ray photoelectron spectroscopy (XPS), and current density-voltage (J-V) curves with a large reverse bias voltage range obtained under dark conditions are used to determine whether GO layers play important roles in blocking the electron transport to the MoO₃/Ag composite anode and prevent MoO₃ diffusion into a photoactive layer under light illumination. Moreover, GO inserted between a photoactive layer and an HEL enhances charge carrier transport and collection and avoids the monomolecular recombination between the photoactive layer and HEL. Photovoltaic parameters and photostability measurements of inverted and forward PSCs have shown that upon introduction of GO, the performance and photostability of PSCs are improved. On adding GO to PSCs, the power conversion efficiency (PCE) increases approximately 5% and 4% and reduces the decay ratio to approximately 50% and 65% of the initial value for the inverted and forward PSCs, respectively.

Fully Solution-Processed n-i-p-Like Perovskite Solar Cells with Planar Junction: How the Charge Extracting Layer Determines the Open-Circuit Voltage

Fully solution-processed direct perovskite solar cells with a planar junction are realized by incorporating a cross-linked [6,6]-phenyl-C61-butyric styryl dendron ester layer as an electron extracting layer. Power conversion efficiencies close to 19% and an open-circuit voltage exceeding 1.1 V with negligible hysteresis are delivered. A perovskite film with superb optoelectronic qualities is grown, which reduces carrier recombination losses and hence increases V _oc .

Nanoporous Anodic Alumina 3D FDTD Modelling for a Broad Range of Inter-pore Distances

The capability of the finite difference time domain (FDTD) method for the numerical modelling of the optical properties of nanoporous anodic alumina (NAA) in a broad range of inter-pore distances is evaluated. FDTD permits taking into account in the same numerical framework all the structural features of NAA, such as the texturization of the interfaces or the incorporation of electrolyte anions in the aluminium oxide host. The evaluation is carried out by comparing reflectance measurements from two samples with two very different inter-pore distances with the simulation results. Results show that considering the texturization is crucial to obtain good agreement with the measurements. On the other hand, including the anionic layer in the model leads to a second-order contribution to the reflectance spectrum.