Enhancement of light harvesting efficiency of perovskite solar cells by using one-dimensional photonic crystals.

We present methyl-ammonium lead iodide perovskite solar cells coupled with one-dimensional photonic crystals (PCs) to achieve enhancement in light harvesting and photocurrent efficiencies. The introduction of PCs as a light reflection layer in the solar cells attributes to the increase in light harvesting efficiency and photocurrent density, which can be tuned by controlling the PC parameters such as the number of layers and layer thickness. Another important feature of the design is the introduction of a thin Au/Ag layer on top, which lets through more than 70% sunlight incident on it into the device, protects the hole transporting layer, and also helps in containing the light reflected from the PC layer into the device for further harvesting. The effects of layer thickness of the perovskite, hole transporting, and metallic contact layers on solar absorption enhancement and photocurrent density are also studied to achieve high power conversion efficiencies. We propose the optimum structural parameters of the considered solar cell structures, which provide the required guidance and also give further opportunities in the design of organo-metal halide perovskite solar cells coupled with PC structures.

Gold-aluminum-based surface plasmon resonance sensor with a high quality factor and figure of merit for the detection of hemoglobin.

A gold (Au) and aluminum (Al)-based surface plasmon resonance (SPR) sensor, with a high-quality factor and figure of merit, for the detection of hemoglobin concentration in human blood is proposed. The sensing performance of a bimetallic Au grating over an Al film-based sensor depends on the thickness of the Al film. The sensor's performance is closely analyzed in terms of well-defined performance parameters: sensitivity, FWHM, and depth of SPR dips in order to optimize the thickness of Al film. With optimized thickness, we could achieve quality factor and figure of merit values of 286.2 RIU-1 and 0.97 deg-1, respectively. Al is chemically unstable, and, to address the oxidation problem, we analyzed the sensor with an ultrathin protective Au layer between the Au grating and Al film. We show that the introduction of an ultrathin Au layer gives stability to the sensor without much affecting the performance of the sensor. The obtained values of quality factor and figure of merit of the proposed sensor are 245.2 RIU-1 and 0.86 deg-1, respectively. We also discuss the potential of hemoglobin detection of the proposed sensor in the near-infrared region. Reported sensitivity of the sensor is 0.62°/dgL-1.

Sensitivity enhancement of a conventional gold grating assisted surface plasmon resonance sensor by using a bimetallic configuration.

A surface plasmon resonance (SPR)-based refractive index sensor using a silver grating fabricated over the gold film is proposed. The performance of the sensor has been evaluated on the basis of sensitivity, full width half maximum (FWHM), and dip strength of the reflection spectrum. Rigorous coupled wave analysis has been utilized to study the effect of grating parameters on sensing performance. Our systematic analysis exhibits that inappropriate grating parameters may lead to poor performance of the sensor. Sensitivity of the conventional gold grating (grating engraved in gold) assisted SPR sensor is obtained to be 321°/RIU. Further, we have shown that sensitivity and FWHM could be improved by using a bimetallic structure that consists of a silver grating on a thin gold film and thereby increases the quality factor. Sensitivity of the proposed structure is 346°/RIU with a quality factor more than 97.46 RIU-1.