Hisham Nasser

Effect of surface type on structural and optical properties of Ag nanoparticles formed by dewetting

Integration of an array of Ag nanoparticles in solar cells is expected to increase light trapping through field enhancement and plasmonic scattering. Requirement of Ag nanoparticle decoration of cell surfaces or interfaces at the macro-scale, calls for a self-organized fabrication method such as thermal dewetting. Optical properties of a 2D array of Ag nanoparticles are known to be very sensitive to their shape and size. We show that these parameters depend on the type of the substrate used. We observe that the average nanoparticle size decreases with increasing substrate thermal conductivity and nanoparticle size distribution broadens with increasing surface roughness.

Fabrication of Ag Nanoparticles Embedded in Al:ZnO as Potential Light-Trapping Plasmonic Interface for Thin Film Solar Cells

Incident photon conversion efficiency of the absorbing materials at either side of a thin film solar module can be enhanced by integrating a plasmonic interface. Silver nanoparticles represent a good candidate that can be integrated to a thin film solar cell for efficient light-trapping. The aim of this work is to fabricate plasmonically active interface consisting of Ag nanoparticles embedded in Al:ZnO that has the potential to be used at the front surface and at the back reflector of a thin film solar cell to enhance light-trapping and increase the photoconversion efficiency. We show that Ag can readily dewet the Al:ZnO surface when annealed at temperatures significantly lower than the melting temperature of Ag, which is beneficial for lowering the thermal budget and cost in solar cell fabrication. We find that such an interface fabricated by a simple dewetting technique leads to plasmonic resonance in the visible and near infrared regions of the solar spectrum, which is important in enhancing the conversion efficiency of thin film solar cells.

High haze nature of textured Al:ZnO with Ag nanoparticles for light management in thin film solar cells

We report on fabrication of plasmonic interfaces consisting of Ag nanoparticles on flat and textured Al:ZnO for use at the front surface of thin film solar cells to enhance light trapping and photo-conversion efficiencies. We show that outstandingly high transmittance haze is achieved from single step HCl surface textured Al:ZnO and demonstrate Ag dewetting on textured and flat Al:ZnO surfaces upon annealing at moderate temperatures. Optical response of these plasmonic interfaces clearly display plasmonic resonances in the visible and near infrared, which is crucial for enhancement of photovoltaic conversion efficiency in thin film solar cells.

Admittance analysis of thermally evaporated-hole selective MoO3 on crystalline silicon

Integration of stoichiometric molybdenum trioxide (MoO3−x) as an effective hole transport layer (HTL) in solar cells is expected to reduce fabrication cost by eliminating the high temperature processes while maintaining high conversion efficiency. In this work we performed a systematic study to extract the electronic properties of vapor-phase deposited MoO3−x thin film and MoO3−x/crystalline silicon interface through capacitance and conductance analysis. Effect of MoO3−x thickness as well as post deposition annealing on series resistance, electrical response, interface and bulk trapped oxide charges were profoundly examined and determined. Moreover, variation in series resistance, behavior of the interface and bulk trapped charges were revealed. Finally, frequency and bias voltage dependence of the series resistance and interface trapped charge were determined

Effect of laser parameters and post-texturing treatments on the optical and electrical properties of laser textured c-Si wafers

Surface plays a crucial role in the performance of crystalline silicon (cSi) based solar cells as it affects both electrical and optical properties. To minimize reflection from the flat surface and thus improve light trapping, the cSi wafers must be textured. For mono-cSi cells, anisotropic alkaline etchants are commonly utilized to create pyramids on the surface. However, this method is not viable for multi-crystalline silicon (mc-Si) wafers due to the presence of different and random crystallographic orientations. In this work, we employed laser texturing, which is an isotropic texturing process, as an alternative texturing method for mc-Si wafers. This approach utilizes a laser process to create pits on the cSi surface. The laser’s processing parameters were justified by performing a series of experiments. After texturing, physical (ultrasonic bath with deionized water) and chemical (in KOH with two different concentrations of 1 and 20%) cleanings with different durations were performed which were esse...