We report a significant enhancement of the electron injection from n-Si bottom cathodes to organics by using a thin layer
of Cs2CO3 as electron injection layer, leading to the reduction of the turn-on voltages and the improvement of the
efficiencies in Alq3 based inverted top-emitting OLEDs with n-Si directly as cathodes. With structure of n-Si/ Cs2CO3 (2
nm)/TPBi (10 nm)/ Alq3 (40 nm)/ NPB (40 nm)/ MoO3 (2 nm)/Ag (20 nm)/ Alq3 (40 nm), where the 10 nm TPBi is hole
blocking layer for improving charge balance in emission zone and the 40 nm Alq3 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/m2 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 p-Si anode by using an effective electron injection layer and a hole blocking layer to realize better charge balance and recombination. With structure of p-Si/SiO2/MoO3 (2 nm)/NPB (40 nm)/Alq (40 nm)/TPBI (10 nm)/Cs2CO3 (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/m2 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 × 1019 cm-3. Widening of bandgap energy by increasing Mg composition was observed by transmission spectrum.