Light Harvesting In Solar Cells Research Articles

Impedance matched thin metamaterials make metals absorbing

Metals are generally considered good reflectors over the entire electromagnetic spectrum up to their plasma frequency. Here we demonstrate an approach to tailor their absorbing characteristics based on the effective metamaterial properties of thin, periodic metallo-dielectric multilayers by exploiting a broadband, inherently non-resonant, surface impedance matching mechanism. Based on this mechanism, we design, fabricate and test omnidirectional, thin (<1 micron), polarization independent, extremely efficient absorbers (in principle being capable to reach A > 99%) over a frequency range spanning from the UV to the IR. Our approach opens new venues to design cost effective materials for many applications such as thermo-photovoltaic energy conversion devices, light harvesting for solar cells, flat panel display, infrared detectors, stray light reduction, stealth and others.

Employing green synthesized silver nanoparticles as light harvesters in nanostructured solar cells

Surface plasmon resonance associated with metallic nanoparticles is an optical phenomenon which can be exploited to improve light harvesting in solar cells. Silver (Ag) nanoparticles (NPs) have attracted attention for solar cell application these days, due to their better light harvesting abilities in the visible range. The quantum dot sensitized solar cells (QDSSCs) are one of the third generation photoelectro chemical solar cells which hold a promise of 44% theoretically but practically achieved 5% photovoltaic efficiency till date. The present work focuses on the use of Ag NPs prepared from a facile green synthesis in improving the efficiency of QDSSC. Ag NPs prepared here use banana sap for reducing the Ag ions. Cadmium sulphide quantum dots sensitized titania (CdS-TiO2) porous photo anode is coated with Ag NPs and solar cell is fabricated with graphite as the counter electrode and polysulfide as electrolyte. Optical absorption studies of photo anode are performed and basic photovoltaic measurements are conducted to evaluate the influence of Ag NPs on the cell performance.

Disordered photonic structures for light harvesting in solar cells

The effect of periodic and disordered photonic structures on the absorption efficiency of amorphous and crystalline Silicon thin-film solar cells is investigated numerically. We show that disordered patterns possessing a short-range correlation in the position of the holes yield comparable, or even superior, absorption enhancements than periodic (photonic crystal) patterns. This work provides clear evidence that non-deterministic photonic structures represent a viable alternative strategy for photon management in thin-film solar cells, thereby opening the route towards more efficient and potentially cheaper photovoltaic technologies.

Semiconductor Nanocrystals as Light Harvesters in Solar Cells.

Photovoltaic cells use semiconductors to convert sunlight into electrical current and are regarded as a key technology for a sustainable energy supply. Quantum dot-based solar cells have shown great potential as next generation, high performance, low-cost photovoltaics due to the outstanding optoelectronic properties of quantum dots and their multiple exciton generation (MEG) capability. This review focuses on QDs as light harvesters in solar cells, including different structures of QD-based solar cells, such as QD heterojunction solar cells, QD-Schottky solar cells, QD-sensitized solar cells and the recent development in organic-inorganic perovskite heterojunction solar cells. Mechanisms, procedures, advantages, disadvantages and the latest results obtained in the field are described. To summarize, a future perspective is offered.

Depleted hole conductor-free lead halide iodide heterojunction solar cells

Lead halide perovskite is an excellent candidate for use as a light harvester in solar cells. Our work presents a depleted hole conductor free CH3NH3PbI3/TiO2 heterojunction solar cell using a thick CH3NH3PbI3 film. The CH3NH3PbI3 formed large crystals which function simultaneously as light harvesters and as hole transport materials. We performed capacitance voltage measurements, which show a depletion region which extends to both n and p sides. The built-in field of the depletion region assists in the charge separation and suppresses the back reaction of electrons from the TiO2 film to the CH3NH3PbI3 film. This depleted hole conductor free CH3NH3PbI3/TiO2 heterojunction solar cell provides a power conversion efficiency of 8% with a current density of 18.8 mA cm−2, the highest efficiency achieved to date for perovskite based solar cells without a hole conductor.

Nanoparticle Stacks with Graded Refractive Indices Enhance the Omnidirectional Light Harvesting of Solar Cells and the Light Extraction of Light‐Emitting Diodes

AbstractIn this study, nanoparticles (NPs) of various types and sizes are arranged to enhance both the omnidirectional light harvesting of solar cells and the light extraction of light emitting diodes (LEDs). A graded‐refractive‐index NP stack can minimize reflectance, not only over a broad range of wavelengths but also at different incident angles; the photocurrent of silicon‐based solar cells an also be significantly improved omnidirectionally. In addition, the optical gradient of an NP stack can also enhance the light‐extraction efficiency of LEDs, due to both the graded refractive index and the moderate surface roughness. Large particles having sizes on the same order of the wavelength of the incident light roughen the LED surfaces further and extract light from beyond the critical angle, as supported by three‐dimensional finite‐difference time‐domain simulations. Using this approach, the photoluminescence intensity can be increased by up to sevenfold. The developed technique: arranging sequences of different NPs in graded‐refractive‐index stacks, and considering their ability to scatter light due to their sizes and optical constants, may also significantly improve the performance of various optoelectronic devices.

Mutual Interplay of Light Harvesting and Triplet Sensitizing in a Perylene Bisimide Antenna−Fullerene Dyad

A flexible organic dyad consisting of a perylene bisimide antenna covalently linked to a [60]fullerene has been synthesized and studied by electrochemistry, steady-state spectroscopy, and time-resolved spectroscopy. We found that the energy absorbed by the perylene bisimide is transferred to the fullerene with an efficiency close to 100%. The fullerene in turn undergoes intersystem crossing followed by triplet energy transfer back to the perylene bisimide with an efficiency of at least 20%. Hence the perylene bisimide unit acts as an antenna for the fullerene, i.e., effectively extending the fullerene absorption far into the visible spectral range, while at the same time the fullerene acts as a triplet sensitizer for the perylene bisimide. This has severe consequences for the exploitation of the dye antenna-fullerene concept for light harvesting in solar cells.