A series of novel metal-free organic sensitizers based on N-annulated perylene derivatives have been designed and synthesized, and exhibit broad absorption spectra in the visible region. The dye-sensitized solar cells exhibit overall conversion efficiencies ranging from 4.90% to 8.28% under AM 1.5 solar conditions.

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Thermal characteristics of GaN-based vertical cavity surface emitting lasers (VCSELs) with three typical structures were investigated both theoretically and experimentally. The simulation results based on a steady state quasi three-dimensional cylindrical model show that the thermal resistance (R th ) is affected by cavity length, mesa size, as well as the bottom distributed Bragg reflector (DBR) size, and the detail further depends on different structures. Among different devices, GaN VCSEL with a hybrid cavity formed by one nitride bottom DBR and another dielectric top DBR is featured with lower R th , which is meanwhile affected strongly by the materials of the epitaxial bottom DBR. The main issues affecting the thermal dissipation in VCSELs with double dielectric DBRs are the bottom dielectric DBR and the dielectric currentconfinement layer. To validate the simulation results, GaN-based VCSEL bonded on a copper plate was fabricated. R th of this device was measured and the results agreed well with the simulation. This work provides a better understanding of the thermal characteristics of GaNbased VCSELs and is useful in optimizing the structure design and improving the device performance.

Four novel metal-free D-A-π-A organic sensitizers (ND01-ND04) based on N-annulated perylene (NP) derivatives as efficient electron donors for dye-sensitized solar cells (DSSCs) are designed. Among them, ND02 featuring bulky 4-methoxyphenyl as the additional electron-donating substituents on the NP unit shows a power conversion efficiency as high as 8.30%.

To meet the requirement of high molar extinction coefficient, broad absorption spectrum, and photo/thermal stability for sensitizers of quasi-solid-state dye-sensitized solar cells (Qs-DSSCs) with reduced film thickness, a novel D-A-π-A configuration organic sensitizer IQ22 was specifically designed, in which the conjugation bridge of cyclopentadithiophene (CPDT) unit was incorporated to widen the light response and enhance molar coefficients for increasing the short-circuit current density (J), and the octane chain on CPDT was targeted for suppressing the charge recombination and improving the open-circuit voltage (V). As a result, the Qs-DSSC based on IQ22 exhibits very promising conversion efficiency as high as 8.76%, with a J of 18.19 mA cm, a V of 715 mV, and a fill factor (FF) of 0.67 under AM 1.5 illumination (100 mW cm), standing out in the Qs-DSSCs utilizing metal-free organic sensitizers.