Traditional transparent conducting oxides (TCOs) have been widely used for various optoelectronic applications, but have the trade-off between conductivity and transmittance. Recently, perovskite oxides, with structural and chemical stability, have exhibited excellent physical properties as new TCOs. We focus on SrVO3-based perovskites with a high carrier concentration and BaSnO3-based perovskites with a high mobility for n-type TCOs. In addition, p-type perovskites are discussed, which can serve as potential future options to couple with n-type perovskites to design full perovskite based devices.
Reliable characterization techniques to accurately quantify the metallization-induced recombination losses as well as contact resistivity losses of screen-printed cells are crucial for successful optimization of the contact grid design. Previously, the dark saturation current density at the contact ( ${J}_{\rm 0c}$ ) is often assumed to be constant for different finger width. Similarly, impact of finger width on contact resistivity ( ${\rho }_{\rm c}$ ) is rarely reported. Therefore, we performed a comprehensive evaluation of ${J}_{\rm 0c}$ and ${\rho }_{\rm c}$ as a function of finger width, spacing as well as firing temperature. We found out that ${J}_{\rm 0c}$ increases from $\approx$ 2000 to $\approx$ 8100 $\text{fA/cm}^{2}$ , when the finger width increases from 60 to 400 $\mu$ m; and ${\rho }_{\rm c}$ decrease from 7.2 to 2.2 $\text{m}{\Omega }\cdot \text{cm}^{2}$ when using a wide-TLM rather than a narrow-TLM structure, for samples fired at 840 $^{\circ }$ C. Based on our cross-sectional and top-down scanning electron microscopy images, we believe that the physical root cause can be explained by the difference in the microstructure formed at the metal–silicon interface during the firing process for the screen-printed contacts.
Novel, high-throughput metrology methods are used in this paper for detailed performance loss analysis of approximately 400 industrial crystalline silicon solar cells, all coming from the same production line. The characterization sequence combines traditional global cell measurements (e.g., current–voltage, Suns- ${V}_{\text{OC}}$ ) with camera-based cell imaging of voltage distribution and power dissipation from photoluminescence and lock-in thermography, respectively. Spatial variations in current collection are visualized using a high-speed external quantum efficiency and reflectance measurement technique. A nondestructive transfer length method (TLM) measurement technique is also implemented, featuring circular TLM structures hidden within the busbars of the cells. The variance of individual loss parameters and their impact on cell performance are quantified for this large group of cells. Based on correlations performed across parameters, recombination losses in the bulk and rear surface of the cell are shown to be the primary limiting factor for the cell efficiency. The nature of these distributions and correlations provide important insights about loss mechanisms in industrial solar cells, helping to prioritize efforts for optimizing the performance of the production line. Additionally, many of the parameters extracted from these techniques can be tied back to incoming material quality issues (e.g., poor bulk carrier lifetime, nonuniform wafer doping) and to individual unit processes (e.g., texturing, phosphorus diffusion, silicon nitride deposition, metallization), allowing the data to be used directly for process control in manufacturing. All of the datasets are made available for download.
We have investigated a novel hybrid nanocomposite thermal interface material (TIM) that consists of silver nanoparticles (AgNPs), silver nanoflakes (AgNFs), and copper microparticles (CuMPs). Continuous metallic network form while AgNPs and AgNFs fuse to join bigger CuMPs upon hot compression, resulting in superior thermal and mechanical performances. The assembly temperature is as low as 125 °C due to the size effect of silver nanoparticulates. The thermal conductivity, k, of the hybrid nanocomposite TIMs is found to be in the range of 15–140 W/mK, exceeding best-performing commercial thermal greases, while comparable to high-end solder TIMs. The dependence of k on the solid packing density and the volume fraction of voids is discussed through comparing to model predictions.