ABSTRACT:We report for the first time on a hole conductor-free mesoscopic lead iodide CH3NH3PbI3(perovskite)/TiO2 heterojunction solar cell, produced by deposition of perovskite nanoparticles from a solution of CH3NH3I and PbI2 in -butyrolactone on a 400nm thick film of TiO2 (anatase) nanosheets exposing (001) facets. An Au film was evaporated on top of the CH3NH3PbI3 served as a back contact. Importantly, the CH3NH3PbI3 nanoparticles act assumes here simultaneously the role of light harvester and hole conductor rendering superfluous the use of an additional hole transporting material. The simple mesoscopic CH3NH3PbI3/TiO2 heterojunction solar cell shows impressive photovoltaic performance with short circuit photocurrent (Jsc) of 16.1 mA/cm 2 , an open circuit photovoltage (Voc) of 0.631 V and a fill factor (FF) of 0.57, corresponding to a light to electric power conversion efficiency (PCE) of 5.5% under standard AM 1.5 solar light of 1000 W/m 2 intensity. At a lower light intensity of 100W/m 2 a PCE of 7.3 % was measured. The advent of such simple solution processed mesoscopic heterojunction solar cells paves the way for new advances to realize low cost, high-efficiency solar cells.

Quasi type-II PbSe/PbS quantum dots (QDs) are employed in a solid state high effi ciency QD/TiO 2 heterojunction solar cell. The QDs are deposited using layer-by-layer deposition on a half-micrometer-thick anatase TiO 2 nanosheet fi lm with (001) exposed facets. Theoretical calculations show that the carriers in PbSe/PbS quasi type-II QDs are delocalized over the entire core/shell structure, which results in better QD fi lm conductivity compared to PbSe QDs. Moreover, PbS shell permits better stability and facile electron injection from the QDs to the TiO 2 nanosheets. To complete the electrical circuit of the solar cell, a Au fi lm is evaporated as a back contact on top of the QDs. This PbSe/PbS QD/TiO 2 heterojunction solar cell produces a light to electric power conversion effi ciency ( η ) of 4% with short circuit photocurrent ( J sc ) of 17.3 mA/cm 2 . This report demonstrates highly effi cient core/shell near infrared QDs in a QD/TiO 2 heterojunction solar cell.

Understanding specific protein-peptide interactions could offer a deep insight into the development of therapeutics for many human diseases. In this work, we designed and synthesized a far-red/near-infrared (FR/NIR) fluorescence light-up probe (DBT-2EEGWRESAI) by simply integrating two tax-interacting protein-1 (TIP-1)-specific peptide ligands (EEGWRESAI) with one 4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole (DBT) unit. We first demonstrated that DBT is an environment-sensitive fluorophore with FR/NIR fluorescence due to its strong charge transfer character in the excited state. Thanks to the environmental sensitivity of DBT, the probe DBT-2EEGWRESAI is very weakly fluorescent in aqueous solution but lights up its fluorescence when the probe specifically binds to TIP-1 protein or polyprotein (ULD-TIP-1 tetramer). It is found that the DBT-2EEGWRESAI/TIP-1 protein and the DBT-2EEGWRESAI/ULD-TIP-1 tetramer could self-assemble into spherical nanocomplexes and a nanofiber network, respectively, which lead to probe fluorescence turn-on through providing DBT with a hydrophobic microenvironment. By virtue of the self-assembly-induced FR/NIR fluorescence turn-on, DBT-2EEGWRESAI can detect and visualize specific protein/polyprotein-peptide interactions in both solution and live bacteria in a high contrast and selective manner.

Perovskite solar cells are one of the most promising alternatives to conventional photovoltaic devices, and extensive studies are focused on device optimization to further improve their performance. A compact layer of TiO 2 is generally used in perovskite solar cells to block holes from reaching the fluorine-doped tin oxide electrode. In this contribution, we engineered a TiO 2 compact layer using Nb doping, which resulted in solar cells with a power conversion efficiency (PCE) of 10.26%, which was higher than that of devices with the same configuration but containing a pristine TiO 2 compact layer (PCE = 9.22%). The device performance enhancement was attributed to the decreased selective contact resistance and increased charge recombination resistance resulting from Nb doping, which was revealed by the impedance spectroscopy measurements. The developed strategy highlights the importance of interface optimization for perovskite solar cells.As one of the most promising alternatives to conventional photovoltaic devices, perovskite solar cells have been intensively investigated in the past few years [1][2][3][4][5][6]. Great progress has been made in the device fabrication, and significant improvement of the device performance has been achieved, as demonstrated by the recently reported efficiency of 19.3%, compared with 3.81%, the efficiency of the first perovskite solar cell reported in 2009 [7, 8]. Moreover, perovskite solar cells with various configurations have also been demonstrated. A hole-blocking layer, in most cases, a compact layer of TiO 2 , is generally used between the FTO conducting substrate and the mesoscopic scaffold and/or perovskite layer to prevent the holes in the perovskite or hole-transporting layer from reaching the FTO substrate [8][9][10][11][12][13][14][15]. The importance of the Nano Research

No abstract