A high throughput surface texturing process for optical and optoelectric devices based on a large-area self-assembly of nanospheres via a low-cost micropropulsive injection (MPI) method is presented. The novel MPI process enables the formation of a well-organized monolayer of hexagonally arranged nanosphere arrays (NAs) with tunable periodicity directly on the water surface, which is then transferred onto the preset substrates. This process can readily reach a throughput of 3000 wafers/h, which is compatible with the high volume photovoltaic manufacturing, thereby presenting a highly versatile platform for the fabrication of periodic nanotexturing on device surfaces. Specifically, a double-sided grating texturing with top-sided nanopencils and bottom-sided inverted-nanopyramids is realized in a thin film of crystalline silicon (28 μm in thickness) using chemical etching on the mask of NAs to significantly enhance antireflection and light trapping, resulting in absorptions nearly approaching the Lambertian limit over a broad wavelength range of 375-1000 nm and even surpassing this limit beyond 1000 nm. In addition, it is demonstrated that the NAs can serve as templates for replicas of three-dimensional conformal amorphous silicon films with significantly enhanced light harvesting. The MPI induced self-assembly process may provide a universal and cost-effective solution for boosting light utilization, a problem of crucial importance for ultrathin solar cells.
Organic emitters play a vital role in determining the overall performance of organic light emitting diode (OLED) devices. Traditional fluorescent emitters can only achieve external quantum efficiency (EQE) of 5%, far below expectation; therefore many efforts have been spent on increasing the EQE of OLEDs. Phosphorescence, thermally activated delayed fluorescence, triplet–triplet annihilation, and hybridized local and charge transfer are the most widely applied approaches to harvest the 75% triplet excitons for luminescence. As for selecting or designing suitable emitters for practical applications, it is strongly demanded to have an overall view about emitters of high exciton utilizing efficiency (EUE) from molecule level, i.e., the four common approaches mentioned above and some latest ones of the doublet, singlet fission, triplet–polar annihilation, and rotationally accessed spin state inversion, and also from the aggregated state such as aggregation‐induced emission. In this review, the current progress of highly efficient emitters is presented, covering the chemical structures, the high‐EUE mechanisms in molecule level and aggregated state, and their applications in OLED devices. This review hopefully will illustrate highly efficient electroluminescent materials and their mechanisms, but more importantly, provide helpful information on how to design or select suitable emitters for specific OLED devices.
Silicon/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) heterojunction solar cells with 16.2% efficiency and excellent stability are fabricated on pyramid-textured silicon substrates by applying a water-insoluble ester as capping layer. This shows that a conformal coating of PEDOT:PSS on textured silicon can greatly improve the junction quality with the main stability failure routes related to the moisture-induced poly(3,4-ethylenedioxythiophene) aggregations and the tunneling silicon oxide autothickening.
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