Dipole-field-assisted charge extraction in metal-perovskite-metal back-contact solar cells

Hybrid organic-inorganic halide perovskites are low-cost solution-processable solar cell materials with photovoltaic properties that rival those of crystalline silicon. The perovskite films are typically sandwiched between thin layers of hole and electron transport materials, which efficiently extract photogenerated charges. This affords high-energy conversion efficiencies but results in significant performance and fabrication challenges. Herein we present a simple charge transport layer-free perovskite solar cell (PSC), comprising only a perovskite layer with two interdigitated gold back-contacts. Charge extraction is achieved via self-assembled molecular monolayers (SAMs) and their associated dipole fields at the metal/perovskite interface. Photovoltages of approximately 600 mV generated by SAM-modified PSCs are equivalent to the built-in potential generated by individual dipole layers. Efficient charge extraction results in photocurrents of up to 12.1 mA/cm2 under simulated sunlight, despite a large electrode spacing.Comment: 18 pages, 5 figure

Imprinting localized plasmons for enhanced solar cells

Imprinted silver nanovoid arrays are investigated via angle-resolved reflectometry to demonstrate their suitability for plasmonic light trapping. Both wavelength- and subwavelength-scale nanovoids are imprinted into standard solar cell architectures to achieve nanostructured metallic electrodes which provide enhanced absorption for improving solar cell performance. The technique is versatile, low-cost and scalable and can be applied to a wide range of organic semiconductors. Absorption features which are independent of incident polarization and weakly dependent on incident angle reveal localized plasmonic modes at the structured interface. Metallic nanostructure–PCPDTBT:PCBM samples demonstrate absorption enhancements of up to 40%. The structured interface provides light trapping, which boosts absorption at wavelengths where the semiconductors absorb poorly

Solution-processed antireflective coating for back-contact perovskite solar cells

Back-contact architectures for perovskite solar cells eliminate parasitic-absorption losses caused by the electrode and charge collection layers but increase surface reflection due to the high refractive index mismatch at the air/perovskite interface. To mitigate this, a ∼85 nm thick layer of poly(methyl methacrylate) (PMMA), with a refractive index between those of air and perovskite, has been applied as an antireflective coating. Transfer matrix modelling is used to determine the ideal PMMA layer thickness, with UV-Vis spectroscopy measurements used to confirm the increase in absorption that arises through the application of the antireflective coating. The deposition of a thin film of PMMA via spin coating onto a solar cell results in a 20–30% relative increase in short circuit current density and stable power output density

SERS from molecules bridging the gap of particle-in-cavity structures

We demonstrate that by combining silver nanoparticles and structured gold SSV surfaces the SERS for those molecules that bridge the nanoparticle–cavity gap is preferentially enhanced using 4-mercaptoaniline and 4-mercaptobenzoic acid as examples

Transparent Long-Pass Filter with Short-Wavelength Scattering Based on <i>Morpho</i> Butterfly Nanostructures

We combine the principles of moth-eye antireflection, Bragg scattering, and thin-film interference to design and fabricate a short-wavelength scattering/long-pass filter with sharp cutoff, high transmission of infrared light, and strong reflection of visible light into high angles. Based on the lamellae-edge features on <i>Morpho didius</i> butterfly wings, nanostructures are self-assembled via sequential one-chamber chemical vapor deposition, metal nanoparticle formation, and wet-chemical etching. Finite-element modeling demonstrates strong (>45%) reflection into the first diffracted order for short wavelengths, while retaining >80% transmission for longer wavelengths. Fabricated nanostructures couple more than 50% of reflected light into angles of >10° while enabling broadband long-pass transmission. Such structures have potential applications in light trapping for tandem solar cells, stealth, and signals processing

Present status and future prospects of perovskite photovoltaics

Solar cells based on metal halide perovskites continue to approach their theoretical performance limits thanks to worldwide research efforts. Mastering the materials properties and addressing stability may allow this technology to bring profound transformations to the electric power generation industr