Effect of annealing treatment on CdS/CIGS thin film solar cells depending on different CdS deposition temperatures

Successful utilization of the inherent capability of wide bandgap materials and architectures for radio frequency (RF) power amplifiers (PAs) necessitates the creation of an alternative thermal management paradigm. Recent “embedded cooling” efforts in the aerospace industry have focused on overcoming the near-junction thermal limitations of conventional electronic materials and enhancing removal of the dissipated power with on-chip cooling. These efforts, focusing on the use of diamond substrates and microfluidic jet impingement, are ushering in a new generation (Gen3) of thermal packaging technology. Following the introduction of a modified Johnson's figure-of-merit (JFOM-k), which includes thermal conductivity to reflect the near-junction thermal limitation, attention is turned to the options, challenges, and techniques associated with the development of embedded thermal management technology (TMT). Record GaN-on-Diamond transistor linear power of 11 W/mm, transistor power fluxes in excess of 50 kW/cm2, and heat fluxes, above 40 kW/cm2, achieved in Defense Advanced Research Projects Agency (DARPA)'s near-junction thermal transport (NJTT) program, are described. Raytheon's ICECool demonstration monolithic microwave integrated circuits (MMICs), which achieved 3.1× the CW RF power output and 4.8× the CW RF power density relative to a baseline design, are used to illustrate the efficacy of Gen3 embedded cooling.

Embedded Cooling for Wide Bandgap Power Amplifiers: A Review

We demonstrate the direct synthesis of CdS thin films by spin coating method with thiol-amine co-solvents system. Annealing of the films at various temperatures has been performed in the air using simple glass protector. The XRD patterns show a strong peak along (110) plane related to cubic lattice while two weak peaks at (002) and (100) planes indicate the hexagonal symmetry for the CdS thin films. The Raman peak at 305 cm−1 also confirms the formation of crystalline CdS thin films. The FTIR study also reveals the formation of CdS thin films. The SEM images reveal the surface uniformity and homogeneity of the CdS thin films. The EDX results indicate nearly stoichiometric CdS thin films. The optical band gap of CdS thin films is ~ 2.4 eV when coated at 2000 rpm and annealed at 300 °C for 5 min. These findings indicate that synthesized CdS films are potential candidates for solution-processed CdTe/CdS solar cells.

A novel synthesis and characterization of transparent CdS thin films for CdTe/CdS solar cells

Present study expounds how post-deposition annealing affects the various structural and optical properties of CdS thin films deposited by chemical bath deposition technique. The structural and morphological changes have been observed by X-ray diffraction (XRD), field emission scanning electron microscopy, Transmission electron microscopy and atomic force microscopy studies; however, the optical and electrical properties of the as deposited and annealed films were studied by UV–Vis spectroscopy and four probe method, respectively. The energy dispersive X-ray analysis confirmed that all as-deposited and annealed films showed almost stoichiometric composition. XRD pattern of the thin films clearly shows the transformation from the cubic structure to the hexagonal structure induced by annealing. The band gaps of the as deposited films were found in the range of 2.41–2.47 eV, while after annealing it decreases due to the decomposition of hydroxides. The electrical resistivity found to decrease approximately 10 times after annealing the as-deposited CdS thin films.

Effect of annealing treatment and deposition temperature on CdS thin films for CIGS solar cells applications

Hierarchical nanoflake-structured CdS thin films have been prepared using chemical bath deposition method at two deposition intervals with different complexing agents. As complexing agents, ammonia and ammonia with triethanolamine or ethylene-diamine-tetra-acetic acid were taken. Structural, optical and morphological studies of the as-deposited CdS films have been studied using X-ray diffraction, UV–Vis and Raman spectroscopy, atomic force and field emission scanning electron microscopy. Compositional analysis reveals that near stoichiometric thin films of CdS were deposited at higher deposition time. X-ray diffraction patterns confirmed the cubic phase of the deposited films and the calculated crystallite sizes increased with higher deposition time while both dislocation densities and micro-strains were found to decrease with increase in deposition time. Field emission scanning electron microscopy shows the formation of hierarchical nanoflakes having small voids at lower deposition time, however, the density of the nanoflakes increases with increase in deposition duration. UV–Vis–NIR spectroscopy was performed in the spectral range 350–1100 nm which confirmed that the synthesized films contain good optical transparency in the range of 85–95% and the calculated bandgaps were found in the range of 2.20–2.42 eV. Raman spectroscopy indicated a strong electron–phonon coupling for films deposited for longer duration as the particle size increased.

Effect of deposition time and complexing agents on hierarchical nanoflake-structured CdS thin films

Effect of thermal annealing on the properties of cadmium sulfide deposited via chemical bath deposition

This paper describes a convection-based alternative to conduction heat spreaders that uses liquid microchannels to remove heat directly from the transistors. The concept connects microchannels etched directly into the die with a hydraulic circuit that includes a piezo-diaphragm pump, thermally-regulated autonomous flow control valves, and a high-efficiency heat exchanger to create a stand-alone, hermetically-sealed cooling module. The first part of the paper reviews the experiments performed to develop the key components in the cooling package. It describes the flow tests that measured the pressure drop characteristics of different microchannel designs, reviews the bench tests used to design the piezo-diaphragm pump, and discusses the process followed to train the shape-memory alloy used for the autonomous flow control valves. The second part presents micro Raman spectroscopy experiments that measured gate temperatures in energized GaN-on-SiC dies cooled by different microchannel designs. These measurements show that the microchannels enable up to a 50% increase in device input power over conventional conduction cooling with no increase in gate temperature. They also quantify how cooling effectiveness varies with channel geometry and show how thermal performance plateaus with increasing coolant flow rate.

Robert Davis

Papers

Effect of thermal annealing on the properties of cadmium sulfide deposited via chemical bath deposition

Experimental development of a near junction microchannel heat spreader

Carrier density in p-type ZnTe with nitrogen and copper doping