Search results for "Solar Cell"
showing 10 items of 410 documents
Perovskite solar cells employing organic charge-transport layers
2013
Thin-film photovoltaics play an important role in the quest for clean renewable energy. Recently, methylammonium lead halide perovskites were identified as promising absorbers for solar cells(1). In the three years since, the performance of perovskite-based solar cells has improved rapidly to reach efficiencies as high as 15%(1-10). To date, all high-efficiency perovskite solar cells reported make use of a (mesoscopic) metal oxide, such as Al2O3, TiO2, or ZrO2, which requires a high-temperature sintering process. Here, we show that methylammonium lead iodide perovskite layers, when sandwiched between two thin organic charge-transporting layers, also lead to solar cells with high power-conve…
Perovskite solar cells prepared by flash evaporation
2015
A simple vacuum deposition method for the preparation of high quality hybrid organic-inorganic methylammonium lead iodide perovskite thin films is reported. When sandwiched in between organic charge transporting layers, such films lead to solar cells with a power conversion efficiency of 12.2%.
Solution-processed bi-layer polythiophene–fullerene organic solar cells
2013
An ionic polymer based on a polythiophene backbone with appended imidazolium moieties was successfully implemented as a donor material in fully solution-processed efficient bi-layer solar cells prepared by the low impact meniscus coating technique. High fill factors and device reproducibility were obtained, even for ultrathin polymer layers, indicating excellent film formation properties and good compatibility with solution processing techniques. The possibility of smooth counter ion exchange, allowing solubility modification and efficiency tuning, enables exploration of new functionalities and other device architectures.
Influence of the cyanine counter anions on a bi-layer solar cell performance
2013
ABSTRACTWe present normal and inverted solution processed bi-layer solar cells using cationic cyanine dyes as the electron donor and a fullerene as the electron acceptor. The cells exhibit high open circuit voltages up to 1 volt showing the optimal alignment of donor and acceptor energy levels. We demonstrate the large effect that cyanine dye counter ions can have on the energetics of the solar cells and how the S-shaped current density vs. voltage (J-V) curves can be avoided.
Minimizing geminate recombination losses in small-molecule-based organic solar cells
2019
Small-molecule-based organic solar cells (OSCs) are a recurrent alternative to polymer-based OSCs. Due to the higher purity and definition of small molecules compared to polymers, the morphological requirements can be more relaxed. Here, we present a series of novel rhodanine-based small-molecule electron donors and blend them with the standard acceptor PC70BM. By performing a target analysis on femtosecond spectroscopy data, we quantify the rates of geminate charge recombination. We are able to reproduce these rates by applying the Marcus–Levich–Jortner equation, using results from quantum chemical calculations. This shows that in a series of differently substituted compounds, one can corr…
Hierarchically Structured Titania Films Prepared by Polymer/Colloidal Templating
2010
Hierarchically structured titania films for application in hybrid solar cells are prepared by combining microsphere templating and sol-gel chemistry with an amphiphilic diblock copolymer as a structure-directing agent. The films have a functional structure on three size scales: (1) on the micrometer scale a holelike structure for reduction of light reflection, (2) on an intermediate scale macropores for surface roughening and improved infiltration of a hole transport material, and (3) on a nanometer scale a mesoporous structure for charge generation. Poly(dimethyl siloxane)-block-methyl methacrylate poly(ethylene oxide) (PDMS-b-MA(PEO)) is used as a structure-directing agent for the prepara…
Correlation between polymer architecture, mesoscale structure and photovoltaic performance in side-chain-modified poly(p-arylene-ethynylene)-alt-poly…
2011
Abstract Recent investigations have shown that an anthracene containing poly( p -arylene-ethynylene)-alt-poly( p -arylene-vinylene) statistical copolymer consisting of a well defined conjugated backbone, along which linear and branched alkoxy side chains are attached in a random manner, yields, compared to its counterparts with regular side chain substitution, an improved performance in polymer [6,6]:-phenyl-C 61 -butyric acid methyl ester (PCBM) bulk-heterojunction solar cells. The microscopic origin for the improved power conversion efficiency ( η ≈ 3.8%) of the statistical copolymer – which is the best in its material class – has not been resolved. We conducted grazing incidence wide-an…
Hydrogen-Bonded Aggregates of Oligoaramide−Poly(ethylene glycol) Block Copolymers
2010
Rod−coil copolymers with an oligomeric rod aggregate on a nanometer length scale, which is important for many applications like e.g. organic photovoltaics. However, this aggregation behavior and the driving forces such as hydrogen bonding and π−π interactions, as well as the role of side groups, are not yet fully understood. Here, we investigated these noncovalent interactions in oligo(p-benzamide)−poly(ethylene glycol) (OPBA−PEG) copolymers using solid-state NMR supported by wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and polarization optical microscopy (POM). It was found that longer OPBAs form layered β-sheet-like aggregates and that these are stabilized …
Strategy for good dispersion of well-defined tetrapods in semiconducting polymer matrices.
2014
The morphology or dispersion control in inorganic/organic hybrid systems is studied, which consist of monodisperse CdSe tetrapods (TPs) with grafted semiconducting block copolymers with excess polymers of the same type. Tetrapod arm-length and amount of polymer loading are varied in order to find the ideal morphology for hybrid solar cells. Additionally, polymers without anchor groups are mixed with the TPs to study the effect of such anchor groups on the hybrid morphology. A numerical model is developed and Monte Carlo simulations to study the basis of compatibility or dispersibility of TPs in polymer matrices are performed. The simulations show that bare TPs tend to form clusters in the m…