Effect of Fullerene Passivation on the Charging and Discharging Behavior of Perovskite Solar Cells: Reduction of Bound Charges and Ion Accumulation.

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.

Amino-Acid-Induced Preferential Orientation of Perovskite Crystals for Enhancing Interfacial Charge Transfer and Photovoltaic Performance.

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.

Near-Infrared-Absorbing and Dopant-Free Heterocyclic Quinoid-Based Hole-Transporting Materials for Efficient Perovskite Solar Cells.

New heterocyclic quinoid-based hole transporting materials (HTMs) with a rigid quinoid core [3,6-di(2H-imidazol-2-ylidene)cyclohexa-1,4-diene] have been synthesized. The new HTMs have good hole mobility (>10  cm  V  s ) and very intense absorption in the near-infrared region extending to >800 nm. High performance perovskite solar cells can be fabricated using these HTMs without dopant.

Hierarchical structured TiO2 photoanodes for dye-sensitized solar cells.

A novel approach has been developed to fabricate hills-like hierarchical structured TiO2 photoanodes for dye-sensitized solar cells (DSSCs). The appropriately aggregated TiO2 clusters in the photoanode layer could cause stronger light scattering and higher dye loading that increases the efficiency of photovoltaic device. For detailed light-harvesting study, different molecular weights of polyvinyl alcohol (PVA) were used as binders for TiO2 nanoparticles (P-25 Degussa) aggregation.