Lasing mechanisms in organic photonic crystal lasers with two-dimensional distributed feedback

We present a detailed experimental and theoretical investigation of the lasing characteristics of organic photonic crystal lasers. These lasers are based on strongly modulated two-dimensional polymer surface relief structures on which thin films of optically active organic materials have been deposited. We determine the in-plane photonic band structure of the corresponding quasiguided modes within an effective two-dimensional model. In addition, we calculate the total (three-dimensional) losses associated with these modes. This allows us to identify the lasing thresholds for square lattice geometries and to understand the emission pattern

Device Performance of Emerging Photovoltaic Materials (Version 3)

Following the 2nd release of the “Emerging PV reports,” the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer-reviewed articles in academic journals since August 2021. Updated graphs, tables, and analyses are provided with several performance parameters, e.g., power conversion efficiency, open-circuit voltage, short-circuit current density, fill factor, light utilization efficiency, and stability test energy yield. These parameters are presented as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application, and are put into perspective using, e.g., the detailed balance efficiency limit. The 3rd installment of the “Emerging PV reports” extends the scope toward triple junction solar cells

Device Performance of Emerging Photovoltaic Materials (Version 3)

Following the 2nd release of the “Emerging PV reports,” the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer-reviewed articles in academic journals since August 2021. Updated graphs, tables, and analyses are provided with several performance parameters, e.g., power conversion efficiency, open-circuit voltage, short-circuit current density, fill factor, light utilization efficiency, and stability test energy yield. These parameters are presented as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application, and are put into perspective using, e.g., the detailed balance efficiency limit. The 3rd installment of the “Emerging PV reports” extends the scope toward triple junction solar cells

Lasing Action In Two-Dimensional Organic Photonic Crystal Lasers With Hexagonal Symmetry

We investigate fluorescence and lasing action from strongly modulated two-dimensional surface relief structures with hexagonal symmetry onto which thin films of optically active organic material have been deposited. As compared with second-order laser structures with square symmetry, these organic photonic crystal lasers exhibit unusual feedback mechanisms. As a result, we observe surface-emitting lasing action with a central beam normal to the surface and a hexagonal emission pattern of side-beams whose direction slightly deviates from the normal. A corresponding theoretical analysis allows us to determine the photonic bandstructure and the low-threshold laser modes in this system. These results agree very well with fluorescence data and confirm the hexagonal lasing pattern and the corresponding emission angles

Comparison of periodic and random structures for scattering in thinfilm microcrystalline silicon solar cells

Random structures are typically used for light trapping in thin-film silicon solar cells. However, theoretically periodic structures can outperform random structures in such applications. In this paper we compare random and periodic structures of similar shape. Both types of structure are based on atomic force microscopy (AFM) scans of a sputtered and etched ZnO layer. The absorption in a solar cell on both structures was calculated and compared to external quantum efficiency (EQE) measurements of samples fabricated on the random texture. Measured and simulated currents were found to be comparable. A scalar scattering approach was used to simulate random structures, the rigorous coupled wave analysis (RCWA) to simulate periodic structures. The length and height of random and periodic structures were scaled and changes in the photocurrent were investigated. A high height/length ratio seems beneficial for periodic and random structures. Very high currents were found for r andom structures with very high roughness. For periodic structures, current maxima were found for specific periods and heights. An optimized periodic structure had a period of = 534 nm and a depth of d = 277 nm. The photocurrent of this structure was increased by 1.6 mA/cm 2 or 15% relative compared to the initial (random) structure in the spectral range between 600 nm and 900 nm

Analytical solution for haze values of aluminium-induced texture (AIT) glass superstrates for a-Si:H solar cells

10.1364/OE.22.000A53Optics Express221A53-A6

Printing of Large-Scale, Flexible, Long-Term Stable Dielectric Mirrors with Suppressed Side Interferences

Dielectric mirrors are wavelength-selective mirrors which are based on thin film interference effects. Their optical band can precisely be adjusted in width, position, and reflectance by the refractive index of the applied materials, the layers' thicknesses, and the amount of deposited layers. Nowadays, they are a well-known light management tool for efficiency enhancement in, for example, semitransparent organic solar cells (OSCs) and light guiding in organic light-emitting diodes (OLEDs). However, most of the dielectric mirrors are still fabricated by lab-scale techniques such as spin-coating or physical vapor deposition under vacuum. Large-scale, fully printed (maximum 20 x 20 cm(2)) dielectric mirrors with adjustable reflectance characteristics are fabricated, using temperatures of maximum 50 degrees C and alcohol-based inks. According to the moderate processing conditions they can be easily deposited not only on rigid glass substrates but also on flexible foils. They show high stability against humidity, light irradiation, and temperature, positioning themselves as good candidates for applications in OLEDs and OSCs. Eventually, by simulations and experiments it is verified that a moderate degree of variations in layer thickness and surface roughness can suppress side interference fringes, while not impacting the main transmittance minimum or the main reflection maximum, respectively

Large-area origination and replication of microstructures with optical functions

Structuring surfaces on a microscopic scale allows to modify their optical properties. The exact tailoring of these properties requires very precise manufacturing techniques. On large areas, mainly replication techniques allow competitive production cost. This paper addresses the challenge of originating and replicating microstructures with optical functions with dimensions between 200nm and 50m on areas of up to half a square meter. The whole experimental process chain is described and discussed. For the microstructure origination, interference lithography was used. An argon ion laser was chosen as a coherent light source at a wavelength of 364nm. Periodic and stochastic interference patterns were recorded in positive photoresist by using large interferometer set-ups. Structures with good homogeneity were originated on areas of up to 4800 cm2 by optimizing the set-up and the photoresist processing. By carefully modeling resulting resist profiles it was possible to orig inate a wide variety of surface-relief profiles including prismatic ones. Different replication techniques like hot compression molding and UV casting are discussed. Some applications of large-area micro-structured films and sheets are presented

Dynamic mechanisms of He single ionization by fast proton impact

Triple-differential ionization cross sections 3 pdcphipdprec, the momentum distributions of singly charged recoil ions transverse to the beam direction as a function of the projectile polar (p), and azimuthal (cphip) scattering angle were measured in order to elucidate the dynamics of 3-MeV H+ on He single ionization. For projectile polar deflections 0.2 p1 mrad and azimuthal scattering angles 0°cphip360°, the kinematic regimes where two-body interactions dominate the three-body momentum exchange of the single-ionization reaction were separated experimentally. © 1992 The American Physical Society