Li-Doped ZnO Electron Transport Layer for Improved Performance and Photostability of Organic Solar Cells

In-Doped ZnO Electron Transport Layer for High-Efficiency Ultrathin Flexible Organic Solar Cells

Sol-gel processed zinc oxide (ZnO) is one of the most widely used electron transport layers (ETLs) in inverted organic solar cells (OSCs). The high annealing temperature (≈200 °C) required for sintering to ensure a high electron mobility however results in severe damage to flexible substrates. Thus, flexible organic solar cells based on sol-gel processed ZnO exhibit significantly lower efficiency than rigid devices. In this paper, an indium-doping approach is developed to improve the optoelectronic properties of ZnO layers and reduce the required annealing temperature. Inverted OSCs based on In-doped ZnO (IZO) exhibit a higher efficiency than those based on ZnO for a range of different active layer systems. For the PM6:L8-BO system, the efficiency increases from 17.0% for the pristine ZnO-based device to 17.8% for the IZO-based device. The IZO-based device with an active layer of PM6:L8-BO:BTP-eC9 exhibits an even higher efficiency of up to 18.1%. In addition, a 1.2-micrometer-thick inverted ultrathin flexible organic solar cell is fabricated based on the IZO ETL that achieves an efficiency of 17.0% with a power-per-weight ratio of 40.4 W g-1, which is one of the highest efficiency for ultrathin (less than 10 micrometers) flexible organic solar cells.

Polymer-Doped SnO2 as an Electron Transport Layer for Highly Efficient and Stable Perovskite Solar Cells

To produce highly efficient and repeatable perovskite solar cells (PSCs), comprehending interfacial loss and developing approaches to ameliorate interfacial features is essential. Nonradiative recombination at the SnO2-perovskite interface in SnO2-based perovskite solar cells (PSCs) leads to significant potential loss and variability in device performance. To improve the quality of the SnO2 electron transport layer, a novel polymer-doped SnO2 matrix, specifically using polyacrylic acid, was developed. This matrix is formed by spin-coating a SnO2 colloidal solution that includes polymers. The polymer aids in dispersing nanoparticles within the substrate and is evenly distributed in the SnO2 solution. As a result of the polymer addition, the density and wetting properties of the SnO2 layer substantially improved. Subsequently, perovskite-based photovoltaic devices comprising SnO2 and Spiro-OMeTAD layers and using (FAPbI3)0.97(MAPbBr3)0.03 perovskite are constructed. These optimized devices exhibited an increased efficiency of 17.2% when compared to the 15.7% power conversion efficiency of the control device. The incorporation of polymers in the electron transport layer potentially enables even better performance in planar perovskite solar cells.

Effect of ZnCl2 assisted chemical bath deposition on preferred orientations and optical properties of ZnO films

Using zinc chloride as an additive assisted with conventional solutions of zinc acetate dihydrate and hexamethylenetetramine, the synthesis of ZnO films by chemical bath deposition was investigated and characterized by x-ray diffraction, field emission scanning electron microscopy, atomic force microscope, photoluminescence (PL) and UV-Vis spectrophotometry. ZnO films with (0002), (101̄2), (112̄2), (112̄0), and (101̄0) preferential growth orientation were prepared by changing the concentration of the introduced zinc chloride. The results of UV-Vis spectrophotometry show that the ZnO films with different preferential growth orientations have optical transmittance of more than 80% in the visible light region. Results from PL show that compared to the typical polar (0002) preferential growth orientation of ZnO, other films with different preferential growth orientations have different visible emissions. It was also confirmed that the concentration of Cl- can affect the defects and preferred orientations of ZnO films. This work enriches the fabrication of ZnO films with different preferential growth orientations and also provides new ideas for the fabrication of ZnO-based transparent nanodevices.

Recent Advances of Doped SnO2 as Electron Transport Layer for High-Performance Perovskite Solar Cells

Perovskite solar cells (PSCs) have garnered considerable attention over the past decade owing to their low cost and proven high power conversion efficiency of over 25%. In the planar heterojunction PSC structure, tin oxide was utilized as a substitute material for the TiO2 electron transport layer (ETL) owing to its similar physical properties and high mobility, which is suitable for electron mining. Nevertheless, the defects and morphology significantly changed the performance of SnO2 according to the different deposition techniques, resulting in the poor performance of PSCs. In this review, we provide a comprehensive insight into the factors that specifically influence the ETL in PSC. The properties of the SnO2 materials are briefly introduced. In particular, the general operating principles, as well as the suitability level of doping in SnO2, are elucidated along with the details of the obtained results. Subsequently, the potential for doping is evaluated from the obtained results to achieve better results in PSCs. This review aims to provide a systematic and comprehensive understanding of the effects of different types of doping on the performance of ETL SnO2 and potentially instigate further development of PSCs with an extension to SnO2-based PSCs.