Organometal halide perovskites are highly promising materials for photovoltaic applications, yet their rapid degradation remains a significant challenge. Here, the light-induced structural degradation mechanism of methylammonium lead iodide (MAPbI3) perovskite films and devices is studied in low humidity environment using X-Ray Diffraction, Ultraviolet-Visible (UV-Vis) absorption spectroscopy, Extended X-ray Absorption Fine Structure spectroscopy, Fourier Transform Infrared spectroscopy, and device measurements. Under dry conditions, the perovskite film degrades only in the presence of both light and oxygen, which together induce the formation of halide anions through donation of electrons to the surrounding oxygen. The halide anions generate free radicals that deprotonate the methylammonium cation and form the highly volatile CH3NH2 molecules that escape and leave pure PbI2 behind. The device findings show that changes in the local structure at the TiO2 mesoporous layer occur with light, even in the absence of oxygen, and yet such changes can be prevented by the application of UV blocking layer on the cells. Our results indicate that the stability of mp-TiO2-MAPbI3 photovoltaics can be dramatically improved with effective encapsulation that protects the device from UV light, oxygen, and moisture.

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A Luminescent Solar Concentrator (LSC) greenhouse and an identical control greenhouse were constructed with photovoltaic (PV) cells attached to the roof panels of both structures. The placement and types of PV cells used in the LSC panels were varied for performance comparisons. Solar power generation was monitored continuously for one year, with leading LSC panels exhibiting a 37% increase in power production compared to the reference. The 22.3 m2 greenhouse was projected to generate a total of 1342 kWh per year, or 57.4 kWh/m2 if it were composed solely of the leading panel of Criss Cross panel design. The LSC panels showed no signs of degradation throughout the trial demonstrating the material's robustness in field conditions.

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The numerous electronic and optoelectronic applications that rely on semiconductors require tuning their properties through doping. Germanium quantum dots (Ge QDs) were successfully doped with bismuth up to 1.5 mol %, which is not achievable in the bulk Ge system. The structures of oleylamine-and dodecanethiol-capped Ge QDs were probed with EXAFS, and the results are consistent with Bi dopants occupying surface lattice sites. Increasing the amount of Bi dopant from 0.50 to 1.5 mol % results in increasing disorder. In particular, the nearestneighbor Bi−Ge bond length is much longer than the Ge−Ge bond length in Ge QDs. Oleylamine to dodecanethiol ligand exchange was shown to partially restore order in doped QDs. Transport measurements of the Bidoped Ge QD thin films revealed that Bi doping leads to a significant increase in dark current and photocurrent. These results indicate that doping can provide a pathway for improving the performance of group IV quantum dots for energy conversion applications including photodiodes and photovoltaic cells.