Here we re-evaluate previously assigned carrier lifetimes as being severely influenced by the decay rate of spatially separated charge carriers.

In x Ga 1−x As 1−y N y / GaAs single quantum wells emitting at room temperature in the wavelength range λ=(1.3–1.55) μm have been studied by photoluminescence (PL). By increasing temperature, we find that samples containing nitrogen have a luminescence thermal stability and a room temperature emission efficiency higher than that of the corresponding N-free heterostructures. The temperature dependence of the PL line shape shows a progressive carrier detrapping from localized to extended states as T is increased. Finally, the extent of the thermal shift of the free exciton energy for different y indicates that the electron band edge has a localized character which increases with nitrogen content.

The role of ions in organo-metal halide perovskites and its impact on optoelectronic device performance remains one of the most intriguing issues in the field. The current−voltage hysteresis often observed in hybrid perovskite solar cells has been assigned to the presence of mobile ions inside the perovskite layer. The difficulty in studying electronic properties of solar cells results from the screening effects as well as slow dynamics of mobile ions, particularly if they are located at the interfaces. In this work, we addressed the distribution of charged species in planar-type methylammonium lead iodine (MAPI) as well as formamidinium lead iodine (FAPI) solar cells by using a modified capacitance−voltage (CV) method without illumination in combination with a Mott−Schottky (MS) analysis of experimental data. The characteristic Mott−Schottky behavior with a linear dependence of C −2 (V), distinctive for a pn-junction, is not visible in pristine devices. Surprisingly, biasing the device in the forward direction results in MS behavior, which is due to the field-driven redistribution of mobile ions from the interface toward the absorber bulk. From the MS analysis, we deduced space charge concentrations of 2.5 × 10 16 and 2.8 × 10 16 cm −3 for the FAPI and the MAPI devices, respectively. However, the junction formation effect is not sustainable, since mobile ions relax to their initial location at ambient conditions. However, if the prebiasing is done at temperatures slightly below room temperature, the pnjunction can be stabilized for the FAPI device. In contrast, the MAPI device shows a rapid redistribution of mobile ions back to the transport layers during the measurement even at lower temperatures. This can be observed in the quite different doping profiles for the two perovskite devices.

Atomic hydrogen irradiation leads to striking effects on the electronic properties of In x Ga 1Ϫx As 1Ϫy N y /GaAs single quantum wells as measured by photoluminescence spectroscopy. The In x Ga 1Ϫx As 1Ϫy N y band-gap energy blueshifts with increasing hydrogen dose and finally saturates at the value of a corresponding reference sample without nitrogen. The luminescence intensity decreases upon hydrogen irradiation with a strong dependence on nitrogen content. The above results have been found in a large set of samples differing for nitrogen and indium content, and are related to the formation of bonds between hydrogen and one or more nitrogen atoms.

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