We study the thermal stability in air of the mixed cation organic-inorganic lead halide perovskites CsFAPb(IBr) and Cs(MAFA)Pb(IBr). For the latter compound, containing both MA and FA ions, thermal decomposition of the perovskite phase was observed to occur in two stages. The first stage of decomposition occurs at a faster rate compared to the second stage and is only observed at relatively low temperatures (T < 150 °C). For the second stage, we find that both decomposition rate and the activation energy have similar values for Cs(MAFA)Pb(IBr) and CsFAPb(IBr), which suggests that the first stage mainly involves reaction of MA and the second stage mainly FA.
We demonstrate unassisted water splitting with >10% solar-to-hydrogen conversion efficiency using series-connected silicon heterojunction solar cells protected by ALD TiO2 in a novel, integrated device architecture.
The hole transport layer (HTL) is one of the key components in planar perovskite solar cells (PSCs). Here, we report a new kind of HTL fabricated using atomic layer deposition (ALD). By alloying TiO 2 with IrO x , we demonstrate that TiO 2 , a well-known electron-selective contact and electron transport layer (ETL) in photovoltaic devices, can behave as an HTL with an appropriately high work function. Perovskite Cs 0.17 FA 0.83 Pb(I 0.83 Br 0.17 ) 3 solar cells including this new hole transport material achieved a power conversion efficiency of 15.8% under AM 1.5G simulated solar irradiation compared to a 14.3% efficiency for otherwise-identical devices incorporating a more standard NiO HTL layer. These results suggest the promise of transition metal oxide alloys synthesized by ALD as hole contact materials for optoelectronic devices, including advanced photovoltaics.
elevated temperatures and UV light. To improve the stability of perovskite solar cells and LEDs, researchers have pursued numerous approaches including depositing hydrophobic coatings on top of perovskites absorbers, [23][24][25][26] device encapsulation [21,[27][28][29] and tuning the composition of perovskites. [30][31][32][33][34] Atomic layer deposited (ALD) metal oxides such as ZnO, Al 2 O 3 , and TiO 2 have been shown to be quite effective as a protection layer for perovskite optoelectronic devices. [35,36] Kim et al. [37] showed that ALD-TiO 2 could make the perovskite solar cells more resistant to elevated temperature and water vapor exposure. In reference, [36] low temperature ALD was utilized to deposit TiO 2 as an electron transport layer and Al 2 O 3 as a solar cell encapsulation layer. A final device including these protection layers was found to retain 97% of its original PCE after a thousand hours exposure to the ambient air. These results suggest that ALD-derived coatings provide a path to the device endurance required for commercial application of perovskite optoelectronic devices including perovskite solar cells, LEDs, and transistors.
In this paper, the hot carrier degradation mechanisms in lightly-doped drain (LDD) n-MOS devices with silicon nitride spacer have been investigated. A low temperature chemical vapor deposited (CVD) SiO2 oxide is used as a post-oxide between source/drain surface and the nitride spacer. The gated-diode measurement in combination with the gate-induced drain leakage (GIDL) current measurement techniques have been used to analyze the stress-induced interface state and oxide charges. For the first time, it was found that the oxide charge but not the interface state generation in the post oxide will dominate the device drain current degradation. Moreover, the CVD post oxide with N2 annealing has been proposed which is able to effectively suppress the generation of oxide charges and significantly improve the device hot carrier reliability. The scaling of gate oxide thickness and the optimization of source/drain junction to improve the device reliability are also demonstrated.
We synthesized inorganic halide perovskite films. We report the kinetics of light induced phase separation of halide perovskites by photoluminescnence characterization. Length scale of the phase separation is studied by X-ray diffraction and cryo-TEM.
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