RESUMEN
Electrical doping of semiconductors is a revolutionary development that enabled many electronic and optoelectronic technologies. While doping of many inorganic and organic semiconductors is well-established, controlled electrical doping of metal halide perovskites (MHPs) is yet to be demonstrated. In this work, efficient n- and p-type electrical doping of MHPs by co-evaporating the perovskite precursors alongside organic dopant molecules is achieved. It is demonstrated that the Fermi level can be shifted by up to 500 meV toward the conduction band and by up to 400 meV toward the valence band by n- and p-doping, respectively, which increases the conductivity of the films. The doped layers are employed in PN and NP diodes, showing opposing trends in rectification. Demonstrating controlled electrical doping by a scalable, industrially relevant deposition method opens the route to developing perovskite devices beyond solar cells, such as thermoelectrics or complementary logic.
RESUMEN
The roll-to-roll printing production process for hybrid organic-inorganic perovskite solar cells (PSCs) demands thick and high-performance solution-based diffusion blocking layers. Inverted (p-i-n) PSCs usually incorporate solution-processed PC70BM as the electron-transporting layer (ETL), which offers good electron charge extraction and passivation of the perovskite active layer grain boundaries. Thick fullerene diffusion blocking layers could benefit the long-term lifetime performance of inverted PSCs. However, the low conductivity of PC70BM significantly limits the thickness of the PC70BM buffer layer for optimized PSC performance. In this work, we show that by applying just enough N-DMBI doping principle, we can maintain the power conversion efficiency (PCE) of inverted PSCs with a thick (200 nm) PC70BM diffusion blocking layer. To better understand the origin of an optimal doping level, we combined the experimental results with simulations adapted to the PSCs reported here. Importantly, just enough 0.3% wt N-DMBI-doped 200 nm PC70BM diffusion blocking layer-based inverted PCSs retain a high thermal stability at 60 °C of up to 1000 h without sacrificing their PCE photovoltaic parameters.
RESUMEN
The mixed ionic-electronic nature of lead halide perovskites makes their performance in solar cells complex in nature. Ion migration is often associated with negative impacts-such as hysteresis or device degradation-leading to significant efforts to suppress ionic movement in perovskite solar cells. In this work, we demonstrate that ion trapping at the perovskite/electron transport layer interface induces band bending, thus increasing the built-in potential and open-circuit voltage of the device. Quantum chemical calculations reveal that iodine interstitials are stabilized at that interface, effectively trapping them at a remarkably high density of â¼1021 cm-3 which causes the band bending. Despite the presence of this high density of ionic defects, the electronic structure calculations show no sub-band-gap states (electronic traps) are formed due to a pronounced perovskite lattice reorganization. Our work demonstrates that ionic traps can have a positive impact on device performance of perovskite solar cells.
RESUMEN
OBJECTIVE: Gestational diabetes mellitus (GDM) was previously found to be an independent risk factor for long-term cardiovascular morbidity of parturients and their offspring. The objective of this study was to investigate the association between family history of diabetes mellitus (DM) in non-diabetic mothers and long-term pediatric cardiovascular hospitalizations of their offspring. STUDY DESIGN: In a hospital-based cohort study, the incidence of cardiovascular disorders was compared between offspring of non-diabetic mothers with and without a family history of DM. Cardiovascular hospitalizations were assessed up until 18years of age according to a predefined set of ICD-9 codes associated with hospitalization of offspring. Exclusion criteria included multiple gestations, mothers with pre-gestational or gestational diabetes, lack of prenatal care, and children with congenital malformations and chromosomal abnormalities. A Kaplan-Meier survival curve was used to compare cumulative hospitalizations incidence. A cox proportional hazards model was performed to control for confounders. RESULTS: A total of 208,728 deliveries were included in the study. Of them, 17,040 (8.2%) offspring were born to non-diabetic mothers with a family history of DM. Significant differences in the rates of IVF, induction of labor, obesity, hypertensive disorders of pregnancy, smoking and birth weight were found between the two study groups. Total cardiovascular hospitalizations were comparable between the study groups (0.6% vs. 0.7%, p=0.416). The Kaplan-Meier survival curve exhibited no difference in the cumulative incidence of total cardiovascular hospitalizations of the offspring (log-rank test, p=0.271). A Cox regression model found that a family history of DM in non-diabetic mothers was not independently associated with long-term cardiovascular hospitalizations of the offspring after controlling for the following confounders: maternal age, birth weight, caesarian section and maternal hypertensive disorders (aHR=1.130, 95% CI 0.930-1.374, p=0.220). CONCLUSION: A family history of DM in non-diabetic parturients, does not increase the risk for cardiovascular hospitalizations of their offspring.
