Tsuchime-like Aluminum Film to Enhance Absorption in Ultra-Thin Photovoltaic Cells.

Ultra-thin solar cells enable materials to be saved, reduce deposition time, and promote carrier collection from materials with short diffusion lengths. However, light absorption efficiency in ultra-thin solar panels remains a limiting factor. Most methods to increase light absorption in ultra-thin solar cells are either technically challenging or costly, given the thinness of the functional layers involved. We propose a cost-efficient and lithography-free solution to enhance light absorption in ultra-thin solar cells-a Tsuchime-like self-forming nanocrater (T-NC) aluminum (Al) film. T-NC Al film can be produced by the electrochemical anodization of Al, followed by etching the nanoporous alumina. Theoretical studies show that T-NC film can increase the average absorbance by 80.3%, depending on the active layer's thickness. The wavelength range of increased absorption varies with the active layer thickness, with the peak of absolute absorbance increase moving from 620 nm to 950 nm as the active layer thickness increases from 500 nm to 10 µm. We have also shown that the absorbance increase is retained regardless of the active layer material. Therefore, T-NC Al film significantly boosts absorbance in ultra-thin solar cells without requiring expensive lithography, and regardless of the active layer material.

Solution-Processed Red, Green, and Blue Quantum Rod Light-Emitting Diodes.

Solution-processed semiconductor nanocrystals are evolving as potential candidates for future display and lighting applications owing to their size-tunable emission, ultrasaturated colors, and compatibility with large-area flexible substrates. Among them, quantum rods (QRs) are emerging materials for optoelectronic applications, offering polarized emission, high light outcoupling efficiency, color purity, and better stability in solid films. However, synthesizing QRs covering the full visible wavelength region has been a big challenge, particularly in the blue range. Herein, we report for the first time the synthesis of red CdSe/CdS, green CdSe/ZnxCd1-xS/ZnS, and blue CdSe/ZnxCd1-xS/ZnS QRs and their application in red, green, and blue QR-based light-emitting diodes (QR-LEDs). We have improved the charge injection balance into the QRs through embedding a poly(methyl methacrylate) (PMMA) layer between the emissive and electron transport layers. The thin PMMA electron-blocking layer (EBL) suppresses the excessive electron flux and thus promotes charge injection balance and pushes the recombination zone back to the QR layer, resulting in 1.35×, 1.2×, and 1.7× peak external quantum efficiency improvement for red, green, and blue QR-LEDs, respectively. The efficiency roll-off of green and blue QR-LEDs with an EBL is less than 50% at maximum current density. The proposed red, green, and blue QR-LEDs open up an avenue toward further improving the light source efficiency and stability focusing on real device applications.

Comparative analysis of opto-electronic performance of aluminium and silver nano-porous and nano-wired layers.

The comparison of optical and electronic properties between squarely and hexagonally arranged nano-porous layers and uniformly arranged nano-wired layers of aluminium and silver was presented. The nano-wired configuration exhibit 20 and 10% higher average transmittance in visible wavelength range in comparison to square and hexagonal nano-porous designs, respectively. The insignificant difference of the transmittance for aluminium and silver nano-porous and nano-wired layers is observed, when interpore/interwire distance is larger than wavelengths of incoming light. This difference becomes considerable at the interpore/interwire distance less than wavelengths of incoming light: silver nano-porous and nano-wired layers possess up to 27% higher transmittance in comparison to aluminium layers.

Theoretical comparison of optical and electronic properties of uniformly and randomly arranged nano-porous ultra-thin layers.

The theoretical comparison of optical and electronic properties of aluminum and silver nano-porous ultra-thin layers in terms of the arrangement and size of the pores was presented. The uniform nano-porous layers exhibit a slightly higher average transmittance (up to 10%) in the wavelength range of the plasmonic response in comparison to the randomly arranged ones. Compared to uniform nano-porous layers, a much larger sheet resistance (up to 12 times) for random nano-porous layers is observed. The uniform and random Ag nano-porous layers possessing the strong plasmonic response over whole visible range can reach an average transmittance of 90 and 80% at the sheet resistance of 10 and 20 Ohm/sq, respectively, which is comparable to widely used ITO electrodes.

Optoelectronic performance optimization for transparent conductive layers based on randomly arranged silver nanorods.

Optoelectronic performance of transparent conductive layers (TCLs) based on randomly arranged silver (Ag) nanorods (NRs) is simulated. Models for calculation of optical and electronic properties were proposed founded on finite-difference time-domain method and percolation theory respectively. Obtained simulation results are well conformed to experimental data. The influence of angle deviation of NR crossings on the transmittance and sheet resistance are demonstrated. The balance between transmittance and sheet resistance which can be easily set by varying the combinations of NR radius and NR number is shown. Our results demonstrate that randomly arranged Ag layers are promising candidates for flexible TCLs.