Cutaneous cryptococcosis erroneously diagnosed as histoplasma capsulatum infection

A 31-year-old patient with stage 4 HIV/AIDS presented with recurrent painful skin ulcers for more than 8 months. These would start as subcutaneous skin nodules, later becoming fluctuant and suppurating and then healing spontaneously (Fig. 1). The patient had lesions on the left wrist, left posterior thigh, right axilla, right posterior calf and right upper eyelid. He had also been diagnosed with extrapulmonary tuberculosis and had been on highly active antiretroviral therapy (HAART) for 8 months and antituberculosis medication (continuation phase). After initial poor adherence to both groups of drugs, compliance had improved. The CD4 count at baseline was 16 cells/µl and the latest result was 80 cells/µl. Histological analysis of a biopsy specimen taken from the right upper eyelid lesion showed granulation tissue with some acute inflammation. Fungal spores were seen in the exudates and stains revealed ‘capsule-deficient’ fungi that were first thought to be Histoplasma, and were reported as such

Reactions at Noble Metal Contacts with Methylammonium Lead Triiodide Perovskites: Role of Underpotential Deposition and Electrochemistry

Chemical reactivity of halide perovskites coupled with a low energy of formation makes it a challenge to characterize material properties and achieve long-term device stability. In this study, we elucidate electrochemical reactions occurring at the methylammonium lead triiodide (MAPbI3)/Au interface. X-ray photoemission spectroscopy is used to identify a type of reduction/oxidation reaction termed underpotential deposition (UPD) involving lead, iodine, and hydrogen occurring at interfaces with noble metals. Changes in surface compositions and oxidation states suggest that UPD derived adsorbates at MAPbI3/Au interfaces lower the energy barrier for release of volatile HI and/or I2catalyzing degradation at exposed contacts. Additionally, comparison to PbI2/Au interfaces demonstrates that the presence of methylammonium/methylamine accelerates the formation of a Pb0 adlayer on the Au. Reactions involving UPD Pb0 can transform the typically anodic (hole collecting) Au to a cathode in a photovoltaic measurement. Cyclic voltammetry reveals electrochemical reaction peaks in indium tin oxide (ITO)/MAPbI3/Au devices occurring within voltage ranges commonly used for perovskite characterization. The electrochemical stability window of this device architecture is measured to be between−0.5 V and 0.9 V. Voltage induced interfacial reactions contribute to reversible electrochemical peaks, hysteresis, switchable perovskite diode polarity, and permanent degradation at larger voltages. These types of surface reactions alter the interface/interphase composition beyond ion accumulation, provide a source for the diffusion of defects, and contribute to electrode material dependent current-voltage hysteresis. Moreover, the results imply fundamental limitations to achieving high device stability with noble metals and/or methylammonium containing perovskites

Curtailing Perovskite Processing Limitations via Lamination at the Perovskite/Perovskite Interface

Standard layer-by-layer solution processing methods constrain lead–halide perovskite device architectures. The layer below the perovskite must be robust to the strong organic solvents used to form the perovskite while the layer above has a limited thermal budget and must be processed in nonpolar solvents to prevent perovskite degradation. To circumvent these limitations, we developed a procedure where two transparent conductive oxide/transport material/perovskite half stacks are independently fabricated and then laminated together at the perovskite/perovskite interface. Using ultraviolet–visible absorption spectroscopy, external quantum efficiency, X-ray diffraction, and time-resolved photoluminesence spectroscopy, we show that this procedure improves photovoltaic properties of the perovskite layer. Applying this procedure, semitransparent devices employing two high-temperature oxide transport layers were fabricated, which realized an average efficiency of 9.6% (maximum: 10.6%) despite series resistance limitations from the substrate design. Overall, the developed lamination procedure curtails processing constraints, enables new device designs, and affords new opportunities for optimization

Degradation of Highly Alloyed Metal Halide Perovskite Precursor Inks: Mechanism and Storage Solutions

Whereas the promise of metal halide perovskite (MHP) photovoltaics (PV) is that they can combine high efficiency with solution-processability, the chemistry occurring in precursor inks is largely unexplored. Herein, we investigate the degradation of MHP solutions based on the most widely used solvents, dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). For the MHP inks studied, which contain formamidinium (FA⁺), methylammonium (MA⁺), cesium (Cs⁺), lead (Pb²⁺), bromide (Br^–), and iodide (I^–), dramatic compositional changes are observed following storage of the inks in nitrogen in the dark. We show that hydrolysis of DMF in the precursor solution forms dimethylammonium formate, which subsequently incorporates into the MHP film to compromise the ability of Cs⁺ and MA⁺ to stabilize FA⁺-based MHP. The changes in solution chemistry lead to a modification of the perovskite film stoichiometry, band gap, and structure. The solid precursor salts are stable when ball-milled into a powder, allowing for the storage of large quantities of stoichiometric precursor materials