Tungsten oxide $\left({\text{WO}}_3\right)$ was inserted as an anode interfacial layer between the photoactive layer and top electrode in inverted polymer solar cells (PSCs) with nanocrystalline titanium dioxide as an electron selective layer. The device with ${\text{WO}}_3$ exhibited a remarkable improvement in power conversion efficiency compared with that without ${\text{WO}}_3$ , which indicated that ${\text{WO}}_3$ efficiently prevented the recombination of charge carriers at the organic/top electrode interface. The dependence of the device performances on ${\text{WO}}_3$ film thickness and different top metal electrodes was investigated. Transparent inverted PSCs with thermally evaporable $\text{Ag}/{\text{WO}}_3$ as a transparent anode were also investigated when introducing a ${\text{WO}}_3$ buffer layer.

Molybdenum trioxide (MoO3) was inserted between the active layer and top electrode in inverted polymer solar cells (PSCs) with nanocrystalline titanium dioxide as an electron selective layer. The performances of structurally identical PSCs with different top electrodes (Au, Ag, and Al) were investigated and compared. The interface between MoO3 and different metals was studied by x-ray photoelectron spectroscopy. The results showed that the performances of devices with different metals are greatly improved due to the incorporation of MoO3 and the open-circuit voltage of devices is relatively insensitive to the choice of the anode metal when MoO3 is introduced.

Nanocrystalline $\mathrm{Ti}{\mathrm{O}}_2$ thin films were prepared by sol-gel method and were then used to fabricate metal-semiconductor-metal ultraviolet photodetectors with Au Schottky contact. It was found that dark current of the fabricated devices was only $1.9\mathrm{nA}$ at $5\mathrm{V}$ applied bias. High responsivity of $199\mathrm{A}∕\mathrm{W}$ was achieved when it was irradiated by the ultraviolet light $(\lambda =260\mathrm{nm})$ . The low dark current and high responsivity maybe attributed to the effect of Schottky barrier in company with neutral semiconductor owing to the wide finger gap of $20\mu \mathrm{m}$ . The devices show a slow time response with a rise time of $6\mathrm{s}$ and a decay time of $15\mathrm{s}$ . The authors deduced that the slow time response was caused by defect traps which were widely distributed in nanocrysal.

In this letter, metal-semiconductor-metal (MSM) ${\text{TiO}}_2$ ultraviolet (UV) detectors with Ni electrodes have been fabricated. ${\text{TiO}}_2$ thin films were prepared by sol-gel method. At 5 V bias, the dark current of the detector with Ni electrode was 1.83 nA. High photoresponse of 889.6 A/W was found under irradiation of 260 nm UV light, which was much higher than those of other wide bandgap UV detectors with MSM structure. The high photoresponse was due to the great internal gain caused by the hole trapping at interface. The rise time of the device was 13.34 ms and the fall time was 11.43 s.