Organometal halide perovskite solar cells (PSCs) are nowadays regarded as a rising star in photovoltaics. In particular, PSCs incorporating oriented TiO2 nanorod (NR) arrays as the electron transport layer (ETL) have attracted significant attention owing to TiO2 NR's superior electron transport abilities and its potential in long-term stable PSCs. In addition to improve the electron-transport ability of TiO2 NRs, the tuning of the band alignments between the TiO2 NR array and the perovskite layer is also crucial for achieving efficient solar cells. This work describes a facile, one-step, solvothermal method for the preparation of tantalum (Ta) doped TiO2 NR arrays for efficient PSCs. It is shown that the trace doping with Ta tunes the electronic structure of TiO2 NRs by a synergistic effect involving the lower 5d orbitals of the doped Ta5+ ions and the reduced oxygen vacancies. The synergistic tuning of the electronic structure improves the band alignment at the TiO2 NR/perovskite interface and boosts the short-circuit current and the fill factor. By using the optimized doped TiO2 NR array as the ETL, a record efficiency of 19.11% was achieved, which is the highest among one-dimensional-array based PSCs.

Perovskite solar cells (PSCs) with TiO2 materials have attracted much attention due to their high photovoltaic performance. Aligned TiO2 nanorods have long been used for potential application in highly efficient perovskite solar cells, but the previously reported efficiencies of perovskite solar cells based on TiO2 nanorod arrays were underrated. Here we show a solvothermal method based on a modified ketone–HCl system with the addition of organic acids suitable for modulation of the TiO2 nanorod array films to fabricate highly efficient perovskite solar cells. Photovoltaic measurements indicated that efficient nanorod-structured perovskite solar cells can be achieved with the length of the nanorods as long as approximately 200 nm. A record efficiency of 18.22% under the reverse scan direction has been optimized by avoiding direct contact between the TiO2 nanorods and the hole transport materials, eliminating the organic residues on the nanorod surfaces using UV–ozone treatment and tuning the nanorod array morphologies through addition of different organic acids in the solvothermal process.Keywords: nanorod array; one-dimensional material; organic lead halide perovskite; solar cell; TiO2

Although low-temperature, solution-processed zinc oxide (ZnO) has been widely adopted as the electron collection layer (ECL) in perovskite solar cells (PSCs) because of its simple synthesis and excellent electrical properties such as high charge mobility, the thermal stability of the perovskite films deposited atop ZnO layer remains as a major issue. Herein, we addressed this problem by employing aluminum-doped zinc oxide (AZO) as the ECL and obtained extraordinarily thermally stable perovskite layers. The improvement of the thermal stability was ascribed to diminish of the Lewis acid–base chemical reaction between perovskite and ECL. Notably, the outstanding transmittance and conductivity also render AZO layer as an ideal candidate for transparent conductive electrodes, which enables a simplified cell structure featuring glass/AZO/perovskite/Spiro-OMeTAD/Au. Optimization of the perovskite layer leads to an excellent and repeatable photovoltaic performance, with the champion cell exhibiting an open-circuit voltage (Voc) of 0.94 V, a short-circuit current (Jsc) of 20.2 mA cm–2, a fill factor (FF) of 0.67, and an overall power conversion efficiency (PCE) of 12.6% under standard 1 sun illumination. It was also revealed by steady-state and time-resolved photoluminescence that the AZO/perovskite interface resulted in less quenching than that between perovskite and hole transport material.Keywords: aluminum doping; perovskite; solar cell; thermally stable; zinc oxide

Microarray technology is a useful tool for nucleic acid detection and has been widely used in biology and related research fields. However, the procedure is labor intensive and time consuming. Microfluidic chip-based microarrays save time with better performance, but the low spot density and probe number limit its applications. To develop high performance microarrays with high spot density within a microchannel, a method is reported here for preparing microarrays in a capillary by generating probe droplet arrays. The probes in droplets are immobilized onto the inner wall of the capillary to form a one-dimensional probe array, and then a sample solution is introduced to hybridize with the probe array. The effect of the capillary's inner diameter was evaluated to realize a high-density probe array. The processes of array generation and probe immobilization were studied to avoid possible cross contamination. The background from probe immobilization during the array generation and incubation was quantified to assure sensitivity. Multiple sample detection was also demonstrated within one capillary. The capillary based microarray assay had high spot density, easy fabrication, fast detection, high sensitivity and multiple sample capacity.Highlights► High-density probe array containing different probes was prepared along the microchannel. ► Fast hybridization and sensitive detection were realized inside the capillary. ► The array developed here also provided the capacity for detection of multiple samples.

New electrolyte sheets based on porous polyethylene membranes for flexible dye-sensitized solar cells have been developed. Ionic liquid electrolytes are accommodated in commercial polyethylene membranes to form the electrolyte sheets. The morphology of membranes and iodine concentrations in ionic liquid are varied. The electrochemical measurement results show that the morphology, pore structure, and iodine concentration affect mass transport in electrolyte sheet, as well as charge transfer between platinum electrode and electrolyte sheet greatly. Based on these electrolyte sheets, lamination method instead of conventional vacuum injection of electrolyte is used to fabricate flexible dye-sensitized solar cells. Optimal device with an open-circuit voltage (Voc) of 0.63 V, a fill factor of 0.58, and a short-circuit current density (Jsc) of 6.17 mA cm−2 at an incident light intensity of 100 mW cm−2 is obtained, which yields a light-to-electricity conversion efficiency of 2.25%.Highlights► A new electrolyte sheet was developed for flexible dye-sensitized solar cells (DSCs). ► It is composed of a porous polyethylene membranes and ionic liquid electrolytes. ► The electrochemical properties of the electrolyte sheets were evaluated. ► High-performance flexible DSCs with the electrolyte sheets were facilely fabricated.