Interfacial engineering of perovskite solar cells (PSCs) is attracting intensive attention owing to the charge transfer efficiency at an interface, which greatly influences the photovoltaic performance. This study demonstrates the modification of a TiO electron-transporting layer with various amino acids, which affects charge transfer efficiency at the TiO /CH NH PbI interface in PSC, among which the l-alanine-modified cell exhibits the best power conversion efficiency with 30% enhancement. This study also shows that the (110) plane of perovskite crystallites tends to align in the direction perpendicular to the amino-acid-modified TiO as observed in grazing-incidence wide-angle X-ray scattering of thin CH NH PbI perovskite film. Electrochemical impedance spectroscopy reveals less charge transfer resistance at the TiO /CH NH PbI interface after being modified with amino acids, which is also supported by the lower intensity of steady-state photoluminescence (PL) and the reduced PL lifetime of perovskite. In addition, based on the PL measurement with excitation from different side of the sample, amino-acid-modified samples show less surface trapping effect compared to the sample without modification, which may also facilitate charge transfer efficiency at the interface. The results suggest that appropriate orientation of perovskite crystallites at the interface and trap-passivation are the niche for better photovoltaic performance.

Novel modification of the TiO2/CH3NH3PbI3interface using glycine as a coupling agent induced higher coverage of perovskite through a two-step solution process.

To elucidate the biologic significance of hepatocyte HBsAg, its expression patterns were correlated with virus replication and liver pathology in 578 liver biopsies taken from chronic HBsAg carriers aged 1 to 80 years. Five major patterns of hepatocyte HBsAg were identified: homogeneous [intense and discrete, (Pattern A), faint and discrete, (Pattern B) and faint and grouped (Pattern C)]; globular or spotty (Pattern D), and marginal (Pattern E). Pattern A was always associated with viremia and also very frequently with membrane HBsAg expression, but rarely with active liver disease. It occurred most commonly in HBeAg-positive carrier children and young adults, reflecting an early immune tolerance phase with active virus replication. Pattern B was also usually associated with viremia, but very commonly associated with active disease (70%), reflecting active virus replication with enhanced immune response. Pattern E (marginal HBsAg), which was always in group distribution resembling a clonal expansion, predominated the HBeAg-negative phase and was associated with absence of viremia and occurred mostly in older adults with inactive bipolar disease spectrum (normal liver/mild disease or cirrhosis/hepatocellular carcinoma); this reflects a late phase of inactive virus replication or integration. Patterns C and D did not correlate well with viremia, but also tended to have inactive diseases as did Pattern E. These findings suggest that hepatocyte HBsAg expression is closely related to the natural course of chronic hepatitis B virus infection.

Ion accumulation of organometal halide perovskites (OHPs) induced by electrode polarization of perovskite solar cells (PSCs) under illumination has been intensely studied and associated with a widely observed current-voltage hysteresis behavior. This work is dedicated to the investigation of the behavior of charged species at the compact TiO/OHP interface with respect to electrode polarization in PSC devices. By providing a comprehensive discussion of open-circuit voltage ( V) buildup and V decay under illumination and in the dark for the PSCs modified with [6,6]-phenyl-C butyric acid methyl ester (PCBM) at the TiO/OHP interface and their corresponding electrochemical impedance spectroscopies (EISs), a justified mechanism is proposed attempting to elucidate the dynamics of interfacial species with respect to the time and frequency domains. Our results demonstrate that the retarded V buildup and decay observed in PSC devices are related to the formation of bound charges in TiO, which is essential to neutralize the oppositely charged ions accumulating at the OHP side. Besides, inserting a thicker PCBM at the TiO/OHP interface as a passivation layer can alleviate the electrode polarization more efficiently as verified by the low dielectric constant measured from EIS. Moreover, photoluminescence measurements indicate that PCBM at the TiO/OHP interface is capable of passivating a trap state and improving charge transfer. However, with respect to the time scale investigated in this work, the reduction of the hysteresis behavior on a millisecond scale is more likely due to less bound charge formation at the interface rather than shallow trap-state passivation by PCBM. After all, this work comprehensively demonstrates the interfacial properties of PSCs associated with PCBM passivation and helps to further understand its impact on charging/discharging as well as device performance.