Efficiency Enhancement of Silicon Heterojunction Solar Cells via Photon Management Using Graphene Quantum Dot as Downconverters.

By employing graphene quantum dots (GQDs), we have achieved a high efficiency of 16.55% in n-type Si heterojunction solar cells. The efficiency enhancement is based on the photon downconversion phenomenon of GQDs to make more photons absorbed in the depletion region for effective carrier separation, leading to the enhanced photovoltaic effect. The short circuit current and the fill factor are increased from 35.31 to 37.47 mA/cm(2) and 70.29% to 72.51%, respectively. The work demonstrated here holds the promise for incorporating graphene-based materials in commercially available solar devices for developing ultrahigh efficiency photovoltaic cells in the future.

Above-11%-efficiency organic-inorganic hybrid solar cells with omnidirectional harvesting characteristics by employing hierarchical photon-trapping structures.

Hierarchical structures consisting of micropyramids and nanowires are used in Si/PEDOT:PSS hybrid solar cells to achieve a power conversion efficiency (PCE) up to 11.48% with excellent omnidirectionality. The structure provides a combined concepts of superior light trapping ability, significant increase of p-n junction areas, and short carrier diffusion distance, improving the photovoltaic characteristics including short-circuit current density, fill factor, and PCE. The enhancement of power generation is up to 253.8% at high incident angles, showing the outstanding omnidirectional operation ability of hybrid cells with hierarchical Si surfaces. This properly designed hierarchical-structured device paves a promising way for developing low-cost, high-efficiency, and omnidirectional solar applications in the future.

Packaging Glass with a Hierarchically Nanostructured Surface: A Universal Method to Achieve Self-Cleaning Omnidirectional Solar Cells.

Fused-silica packaging glass fabricated with a hierarchical structure by integrating small (ultrathin nanorods) and large (honeycomb nanowalls) structures was demonstrated with exceptional light-harvesting solar performance, which is attributed to the subwavelength feature of the nanorods and an efficient scattering ability of the honeycomb nanowalls. Si solar cells covered with the hierarchically structured packaging glass exhibit enhanced conversion efficiency by 5.2% at normal incidence, and the enhancement went up to 46% at the incident angle of 60°. The hierarchical structured packaging glass shows excellent self-cleaning characteristics: 98.8% of the efficiency is maintained after 6 weeks of outdoor exposure, indicating that the nanostructured surface effectively repels polluting dust/particles. The presented self-cleaning omnidirectional light-harvesting design using the hierarchical structured packaging glass is a potential universal scheme for practical solar applications.

Si Hybrid Solar Cells with 13% Efficiency via Concurrent Improvement in Optical and Electrical Properties by Employing Graphene Quantum Dots.

By employing graphene quantum dots (GQDs) in PEDOT: PSS, we have achieved an efficiency of 13.22% in Si/ PEDOT: PSS hybrid solar cells. The efficiency enhancement is based on concurrent improvement in optical and electrical properties by the photon downconversion process and the improved conductivity of PEDOT: PSS via appropriate incorporation of GQDs. After introducing GQDs into PEDOT: PSS, the short circuit current and the fill factor of rear-contact optimized hybrid cells are increased from 32.11 to 36.26 mA/cm(2) and 62.85% to 63.87%, respectively. The organic-inorganic hybrid solar cell obtained herein holds the promise for developing photon-managing, low-cost, and highly efficient photovoltaic devices.

Realizing high-efficiency omnidirectional n-type Si solar cells via the hierarchical architecture concept with radial junctions.

Hierarchical structures combining micropyramids and nanowires with appropriate control of surface carrier recombination represent a class of architectures for radial p-n junction solar cells that synergizes the advantageous features including excellent broad-band, omnidirectional light-harvesting and efficient separation/collection of photoexcited carriers. The heterojunction solar cells fabricated with hierarchical structures exhibit the efficiency of 15.14% using cost-effective as-cut Czochralski n-type Si substrates, which is the highest reported efficiency among all n-type Si nanostructured solar cells. We also demonstrate the omnidirectional solar cell that exhibits the daily generated power enhancement of 44.2% by using hierarchical structures, as compared to conventional micropyramid control cells. The concurrent improvement in optical and electrical properties for realizing high-efficiency omnidirectional solar cells using as-cut Czochralski n-type Si substrates demonstrated here makes a hierarchical architecture concept promising for large-area and cost-effective mass production.