We report a significant enhancement of the electron injection from <i>n</i>-Si bottom cathodes to organics by using a thin layer
of Cs<sub>2</sub>CO<sub>3</sub> as electron injection layer, leading to the reduction of the turn-on voltages and the improvement of the
efficiencies in Alq<sub>3</sub> based inverted top-emitting OLEDs with <i>n</i>-Si directly as cathodes. With structure of <i>n</i>-Si/ Cs<sub>2</sub>CO<sub>3</sub> (2
nm)/TPBi (10 nm)/ Alq<sub>3</sub> (40 nm)/ NPB (40 nm)/ MoO<sub>3</sub> (2 nm)/Ag (20 nm)/ Alq<sub>3</sub> (40 nm), where the 10 nm TPBi is hole
blocking layer for improving charge balance in emission zone and the 40 nm Alq<sub>3</sub> layer on Ag anode is the capping layer
for improving light out-coupling efficiency, the inverted top-emitting OLEDs show a turn on voltage of 6 V and a
driving voltage of 10 V for 100 cd/m<sup>2</sup> with a maximum efficiency of around 1.5 cd/A, which are superior compared to
the relevant results ever reported.
We report improved efficiency in Alq based top-emitting OLEDs with <i>p</i>-Si anode by using an effective electron injection layer and a hole blocking layer to realize better charge balance and recombination. With structure of <i>p</i>-Si/SiO<sub>2</sub>/MoO<sub>3</sub> (2 nm)/NPB (40 nm)/Alq (40 nm)/TPBI (10 nm)/Cs<sub>2</sub>CO<sub>3</sub> (2 nm)/Ag (20 nm)/Alq (40 nm), where the 40 nm Alq capping layer on top Ag cathode was used to improve out-coupling efficiency, the devices show a turn on voltage of 5.5 V and a driving voltage of 10 V for 100 cd/m<sup>2</sup> with a maximum efficiency of exceeding 1.2 cd/A and a maximum power efficiency of 0.4 lm/W, which are comparable with the conventional OLEDs and encouraging and promising for Si based OLEDs and optoelectronics.
Recently the growth techniques of single-crystalline ZnO film promote much attention to ZnO-related materials for electronic and optoelectronic applications. ZnO and ZnMgO films were grown by radical-source molecular beam epitaxy, and the epilays on a-plane sapphire substrates had a superior quality in crystallographic, optical and electrical properties. The surface during growth was monitored by a reflection high-energy electron diffraction (RHEED) system. After the growth, these films were characterized by Field emission scanning electronic miroscopy, transmission spectrum, photoluminescence (PL) using 325 nm line of a He-Cd laser, and electrical properties were measured by Hall measurement. The n-type doping with Al was successfully performed up to 5 × 10<sup>19</sup> cm<sup>-3</sup>. Widening of bandgap energy by increasing Mg composition was observed by transmission spectrum.