Keywords : solar cells

Graphene micromesh for transparent conductive films application 

Ryousuke Ishikawa; Hiroki Nishida; Hiro Fukushima; Sho Watanabe; Sohei Yamazaki; Gilgu Oh; Nozomu Tsuboi

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 417-420
DOI: 10.5185/amlett.2019.2238

In order to improve the properties of the graphene transparent conductive film, we developed a process of O2 plasma patterning graphene using a metal mesh as an etching mask. The CVD growth conditions of high-quality multilayer graphene samples consisting of 400 layers or more were found using Ni foil, and the R sheet = 3.4 ± 0.6 Ω/sq. was achieved. The best performance of graphene micromesh based transparent conductive films so far was R sheet = 22.2 Ω/sq. at T = 47.1 ± 1.9 %. According to theoretical calculations based on the combined resistance of the two-dimensional resistance lattice circuit, a combined resistance of 46.8 Ω can be realized at T = 90%.

Low temperature processed efficient and stable perovskite solar cell

Ashraf Uddin; Md Arafat Mahmud; Naveen Kumar Elumalai; Mushfika Baishakhi Upama; Dian Wang; Faiazul Haque; Cheng Xu

Advanced Materials Letters, 2019, Volume 10, Issue 2, Pages 98-106
DOI: 10.5185/amlett.2019.2050

MA0.6FA0.4PbI3 material based efficient and stable perovskite solar cells (PSCs) are fabricated by electron transport layer (ETL) interfacial modification. The highest power conversion efficiency (PCE) of device was ~ 17%. Cesium acetate and cesium carbonate were used with low temperature processed sol-gel ZnO ETL for interface modifications. Low leakage current and enhanced dark injection current are observed from dark current-voltage measurement. From the electrochemical impedance spectroscopy (EIS) measurement higher recombination resistance and lower interfacial contact resistance are observed in the PSC devices. Mott-Schottky analysis also shows the higher flat-band potential and enhanced device performance with cesium acetate ETL. Cesium acetate related ZnO ETL has large grain size which leads to reduce the device series resistance and contact resistance in PSC compared to cesium carbonate ETL related device. Perovskite film on cesium acetate ETL has better surface morphology, topography and hydrophobicity characterization compared to perovskite film grown on cesium carbonate ETL film. The material work function and electron injection barrier are also investigated by X-Ray photoelectron spectroscopy (XPS) measurement and ultraviolet photoelectron spectroscopy (UPS). From electrochemical impedance spectroscopy measurements the charge transport behaviour and trap-assisted carrier recombination are estimated. Fabricated PSCs device stability has been measured for a month-long degradation study. The PSC device stability is observed four times higher with cesium acetate PSCs compared to cesium carbonate ETL related PSCs. The overall device PCE is around 82% higher with cesium acetate compared to cesium carbonate devices. 

Spectroscopic investigation of charge and energy transfer in P3HT/GO nanocomposite for solar cell applications

Fokotsa V. Molefe; Mohammed Khenfouch; Mokhotjwa S. Dhlamini; Bakang M. Mothudi

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 246-250
DOI: 10.5185/amlett.2017.1409

As the world demand for energy continue to increase, it is vital to improve renewable energy technologies that will replace conventional fossil fuels. Carbonaceous graphene oxide (GO) is a promising nanomaterial, easy to prepare and scale up to commensurate with industrial requirements. The nanocomposite was prepared in the form of layered structure of GO nanomaterials and poly (3-hexylthiophene) (P3HT) for photovoltaic applications. The X-ray diffraction (XRD) revealed the interaction of P3HT with GO through decrease in lattice spacing. It was evident from scanning electron microscopy (SEM) that the presence of P3HT in GO modified flower like structure to the flaky structures. The interaction of GO with P3HT is presented by various vibrational frequencies in Fourier Transform infrared spectroscopy (FTIR). The increased absorbance and broadening of absorption was observed in the UV-vis spectrum for nanocomposite due to ionic interaction between P3HT and GO. The tunable photoluminescence (PL) measurements showed quenching and shifting of emission spectrum due to charge and energy-transfer. The nanocomposite establish the formation and existence of energy levels upon interaction of GO with P3HT which enhances charge transport. This work provides the direction on coating of thin films for photovoltaic device fabrication. Copyright © 2017 VBRI Press.

Doping Sensitive Optical Scattering In Zinc Oxide Nanostructured films For Solar Cells

Ratheesh R. Thankalekshmi; Samwad Dixit; A. C. Rastogi

Advanced Materials Letters, 2013, Volume 4, Issue 1, Pages 9-14
DOI: 10.5185/amlett.2013.icnano.137

The nanostructured ZnO thin films are used in solar cells as heterojunction window layer as well as to enhance the junction area. Nanostructures also offer advantage of light scattering property to transmit more light into the absorber layer of solar cells. The optical and light scattering property of the nanostructured ZnO thin films doped with Al and Cu have been studied. The homogeneously doped ZnO nanostructured films were synthesized by a flux sublimation technique at ~ 300°C temperature. The structural studies show hexagonal nanocrystal growth in Al doped ZnO film and nanowire structure in Cu doped ZnO film. These doped ZnO films consistently showed two direct band gaps. The low energy band gap of Al and Cu- doped ZnO films originates from the macroscopic structural feature in the film, and the higher energy band gap due to the quantum confinement of nanostructure clusters in the film. Increased transmission in the lower wavelength region is caused by the forward light scattering by the nanostructure. Simulation of the optical absorption spectra of the Al and Cu- doped ZnO films using the modified Mie scattering theory shows consistent match with the experimental absorption spectra. The results show that increased forward scattering of light could be harvested by increasing the nanoparticle density which will enhance the photocurrent generation from the thin film solar cells by using doped ZnO nanostructured film as a window layer or as a transparent conducting electrode.