An Indium-Free Anode for Large-Area Flexible OLEDs: Defect-Free Transparent Conductive Zinc Tin Oxide

Flexible large-area organic light-emitting diodes (OLEDs) require highly conductive and transparent anodes for efficient and uniform light emission. Tin-doped indium oxide (ITO) is the standard anode in industry. However, due to the scarcity of indium, alternative anodes that eliminate its use are highly desired. Here an indium-free anode is developed by a combinatorial study of zinc oxide (ZnO) and tin oxide (SnO2), both composed of earth-abundant elements. The optimized Zn-Sn-O (ZTO) films have electron mobilities of up to 21 cm(2) V-1 s(-1), a conductivity of 245 S cm(-1), and <5% absorptance in the visible range of the spectrum. The high electron mobilities and low surface roughness (<0.2 nm) are achieved by producing dense and void-free amorphous layers as confirmed by transmission electron microscopy. These ZTO layers are evaluated for OLEDs in two anode configurations: i) 10 cm(2) devices with ZTO/Ag/ZTO and ii) 41 cm(2) devices with ZTO plus a metal grid. The ZTO layers are compatible with OLED processing steps and large-area white OLEDs fabricated with the ZTO/grid anode show better performance than those with ITO/grid anodes. These results confirm that ZTO has the potential as an In-free and Earth-abundant alternative to ITO for large-area flexible OLEDs

Towards large area stable perovskite solar cells and modules

In order to commercialize the perovskite solar cells (PSC) technology, efficient and industrial deposition methods over large areas have to be adopted, and the device architectures have to provide long term stability. In this work we combine several upscalable deposition methods to develop a stable semitransparent PSC. The control of the uniformity of perovskite crystallization by tailoring the ink formulation and the drying process was pursued in order to drastically reduce the efficiency losses over an area increase of 3 orders of magnitude (from 0.04 to 100 cm2). When adopting sputtered ITO as top electrode, the stack retains up to 90% of the initial performance after 1000hrs at 85 °C. The use of laser patterning to define P1 P2 and P3 scribes for series interconnected modules enables the fabrication of thermally stable minimodule (4cm2) and large module (100cm2). Finally an outlook on the use of the perovskite device as top cell in a 4T tandem architecture with commercial c-Si cells will be provided