Surface Micro-/Nanotextured Hybrid PEDOT:PSS-Silicon Photovoltaic Cells Employing Kirigami Graphene.

Kirigami graphene allows a two-dimensional material to transform into a three-dimensional structure, which constitutes an effective transparent electrode candidate for photovoltaic (PV) cells having a surface texture. The surface texture of an inverted pyramid was fabricated on a Si substrate using photolithography and wet etching, followed by metal-assisted chemical etching to obtain silicon nanowires on the surface of the inverted pyramid. Kirigami graphene with a cross-pattern array was prepared using photolithography and plasma etching on a copper foil. Then, kirigami graphene was transferred onto hybrid heterojunction PV cells with a poly(ethylene terephthalate)/silicone film. These cells consisted of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as the p-type semiconductor, Si(100) as the inorganic n-type semiconductor, and a silver comb electrode on top of PEDOT:PSS. The conductivity of PEDOT:PSS was greatly improved. This improvement was significantly higher than that achieved by the continuous graphene sheet without a pattern. Transmission electron microscopy and Raman spectroscopy results revealed that the greater improvement with kirigami graphene was due to the larger contact area between PEDOT:PSS and graphene. By using two-layer graphene having a kirigami pattern, the power conversion efficiency, under simulated AM1.5G illumination conditions, was significantly augmented by up to 9.8% (from 10.03 to 11.01%).

Improving Efficiency of Multicrystalline Silicon and CIGS Solar Cells by Incorporating Metal Nanoparticles.

This work studies the use of gold (Au) and silver (Ag) nanoparticles in multicrystalline silicon (mc-Si) and copper-indium-gallium-diselenide (CIGS) solar cells. Au and Ag nanoparticles are deposited by spin-coating method, which is a simple and low cost process. The random distribution of nanoparticles by spin coating broadens the resonance wavelength of the transmittance. This broadening favors solar cell applications. Metal shadowing competes with light scattering in a manner that varies with nanoparticle concentration. Experimental results reveal that the mc-Si solar cells that incorporate Au nanoparticles outperform those with Ag nanoparticles. The incorporation of suitable concentration of Au and Ag nanoparticles into mc-Si solar cells increases their efficiency enhancement by 5.6% and 4.8%, respectively. Incorporating Au and Ag nanoparticles into CIGS solar cells improve their efficiency enhancement by 1.2% and 1.4%, respectively. The enhancement of the photocurrent in mc-Si solar cells is lower than that in CIGS solar cells, owing to their different light scattering behaviors and material absorption coefficients.