In conventional crystalline silicon (Si) homojunction solar cells, a strategy of doping by transporting phosphorus or boron impurities into Si is commonly used to build Ohmic contacts at rear electrodes. However, this technique involves an energy intensive, high temperature (~ 800 ℃) process and toxic doping materials. Black phosphorus (BP) is a two-dimensional, narrow bandgap semiconductor with high carrier mobility that exhibits broad light harvesting properties. Here, we place BP: zinc oxide (ZnO) composite films between Si and aluminum (Al) to improve their contact. Once the BP harvests photons with energies below 1.1 eV from the crystalline Si, the ZnO carrier concentration increases dramatically due to charge injection. This photo-induced doping results in a high carrier concentration in the ZnO film, mimicking the modulated doping technique used in semiconductor heterojunctions. We show that photo-induced carriers dramatically increase the conductivities of the BP-modified ZnO films, thus reducing the contact resistance between Si and Al. A photovoltaic power conversion efficiency of 15.2% is achieved in organic-Si heterojunction solar cells that use a ZnO: BP layer. These findings demonstrate an effective way of improving Si/metal contact via a simple, low temperature process.

Solar energy is one of the most popular clean energy sources and is a promising alternative to fulfill the increasing energy demands of modern society. Solar cells have long been under intensive research attention for harvesting energy from sunlight with a high power-conversion efficiency and low cost. However, the power outputs of photovoltaic devices suffer from fluctuations due to the intermittent instinct of the solar radiation. Integrating solar cells and energy- storage devices as self-powering systems may solve this problem through the simultaneous storage of the electricity and manipulation of the energy output. This review summarizes the research progress in the integration of new-generation solar cells with supercapacitors, with emphasis on the structures, materials, performance, and new design features. The current challenges and future prospects are discussed with the aim of expanding research and development in this field.

We have carried out a comprehensive study on the formation mechanism of Au nanorods (AuNRs) in binary surfactant mixtures composed of quaternary ammonium halide and sodium oleate (NaOL). We identify the cetyltrimethyl ammonium (CTA)-Br-Ag⁺ complex as the key ingredient in directing the anisotropic growth of AuNRs. Based on the improved understanding of the cooperative interactions among CTA⁺, Br^– and Ag⁺, we further demonstrate that AgBr, which is readily solubilized by the cetyltrimethyl ammonium bromide (CTAB) or cetyltrimethyl ammonium chloride (CTAC) micelles, can be employed as the combined source of Ag⁺ and Br^– for the preparation of AuNRs. The growth of high-quality AuNRs can be completed within 15 min under extremely low bromide content (0.1 mM).

We demonstrate that charge carrier diffusion lengths of two classes of perovskites, CH₃NH₃PbI_3-xCl_x and CH₃NH₃PbI₃, are both highly sensitive to film processing conditions and optimal processing procedures are critical to preserving the long carrier diffusion lengths of the perovskite films. This understanding, together with the improved cathode interface using bilayer-structured electron transporting interlayers of [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM)/ZnO, leads to the successful fabrication of highly efficient, stable and reproducible planar heterojunction CH₃NH₃PbI_3-xCl_x solar cells with impressive power-conversion efficiencies (PCEs) up to 15.9%. A 1-square-centimeter device yielding a PCE of 12.3% has been realized, demonstrating that this simple planar structure is promising for large-area devices.