Dan Wang,Shuang Gao,Chuang Li,Yinglin Wang,Hancheng Zhu,Yichun Liu,Xintong Zhang
Efficient activation of donor-type dopants is important for promoting the photoelectrochemical (PEC) performance of semiconductor photoanodes. High temperature annealing, the most often-adopted method, can active the dopants, but is accompanied by serious deterioration of the conductive substrate. Hence, it still remains a challenge to develop a new method to activate the dopants in semiconductor photoanodes deposited on a substrate that is not resistant to high temperature. Herein, we report a pulse laser annealing (PLA) strategy to activate titanium dopant in hematite photoanodes at room temperature to improve the PEC performance for water splitting. A short treatment with 450 nm nanosecond yttrium aluminum garnet (YAG) laser (20 pulses, 30 mJ cm −2 per pulse) causes crystallinity improvement and surface roughening of hematite photoanodes without destroying the fluorine doped SnO 2 (FTO) conductive glass substrate, and results in a 1.85-fold increased photocurrent density (0.484 mA cm −2 , 1.23 V vs. RHE) of Ti-doped hematite photoanodes (5% doping level, Ti:Fe 2 O 3 -PLA). The charge transfer efficiency at the surface of Ti:Fe 2 O 3 -PLA was approximately two-fold higher than Ti:Fe 2 O 3 , and a 10.1-fold increased donor density (1.29 × 10 19 cm −3 ) was achieved, demonstrating the potential of PLA treatment for activating doped semiconductor photoanodes at room temperature.
Solution processed metal oxide thin-film transistors (MO-TFTs) have gained momentum in recent years and opened new horizons for their extended applications in thin-film optoelectronics. Unfortunately, the relatively high processing temperature has become the main limitation for their commercial application in flexible electronics. In this work, ultrashort femtosecond (fs) laser pulses were used for the annealing of printed InGaZnO TFT arrays with low temperature and fast processing. The high transient intensity and negligible heat-affected zone is beneficial to the effective conversion of precursor to metal-oxide lattices, which was also verified by the x-ray photoelectron spectroscopy analysis. Moreover, for the first time, based on optical engineering method, dielectric mirrors (DMs) is proposed to realize reflection of photon irradiation and protect the underlying polymer substrate. TFTs on polyethylene naphthalate (PEN) substrate with polymer insulator exhibited a mobility of 4.24 cm2 V−1 s−1, along with good mechanical stability. The mechanism of DMs for the improvement of the device performance was systematically investigated based on laser-matter interaction, optical structure and photon transport. DMs can reduce laser-induced pressure and variation of dielectric properties in PEN substrate resulting from the impact ionization due to a strong nonlinear multi-photon absorption. Our work clearly demonstrated that flexible MO-TFTs can be simply fabricated with fs-laser annealing. More importantly, this novel method is applicable for a wide range of MO and polymer substrates, by solving the incompatibility of solution processed MO and polymer substrates due to high processing temperature. Therefore, the proposed method showed tremendous potential to be applicable in flexible electronics such as sensors, display and circuits.
Silin Han,Chongyang Li,Yuhang Chen,Yunwen Wu,Ming Li,Tao Hang
In this paper, the changes in microstructure and conductivity of the films before and after thermal and laser annealing are observed, which corresponds to various combinations of crystallite sizes and impurity densities. The results show that the impurities promote grain boundary migration at larger initial crystallite sizes, which contradicts previous reports. This is because the rate of grain growth is determined by the driving force and resistance to grain growth, the former provided by the energy of grain boundaries and the impurities outside the nanograin boundaries, and the latter by the impurities enriched within the boundaries. Additionally, laser annealing is more effective than thermal annealing in stimulating impurity diffusion, resulting in a reduced influence of impurities on grain growth.
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