Lead-Free Halide Double Perovskites via Heterovalent Substitution of Noble Metals

(2016)

Authors:

George Volonakis, Marina R Filip, Amir Abbas Haghighirad, Nobuya Sakai, Bernard Wenger, Henry J Snaith, Feliciano Giustino

Hydrophobic Organic Hole Transporters for Improved Moisture Resistance in Metal Halide Perovskite Solar Cells.

ACS applied materials & interfaces 8:9 (2016) 5981-5989

Authors:

Tomas Leijtens, Tommaso Giovenzana, Severin N Habisreutinger, Jonathan S Tinkham, Nakita K Noel, Brett A Kamino, Golnaz Sadoughi, Alan Sellinger, Henry J Snaith

Abstract:

Solar cells based on organic-inorganic perovskite semiconductor materials have recently made rapid improvements in performance, with the best cells performing at over 20% efficiency. With such rapid progress, questions such as cost and solar cell stability are becoming increasingly important to address if this new technology is to reach commercial deployment. The moisture sensitivity of commonly used organic-inorganic metal halide perovskites has especially raised concerns. Here, we demonstrate that the hygroscopic lithium salt commonly used as a dopant for the hole transport material in perovskite solar cells makes the top layer of the devices hydrophilic and causes the solar cells to rapidly degrade in the presence of moisture. By using novel, low cost, and hydrophobic hole transporters in conjunction with a doping method incorporating a preoxidized salt of the respective hole transporters, we are able to prepare efficient perovskite solar cells with greatly enhanced water resistance.

Monodisperse Dual-Functional Upconversion Nanoparticles Enabled Near-Infrared Organolead Halide Perovskite Solar Cells.

Angewandte Chemie (International ed. in English) 55:13 (2016) 4280-4284

Authors:

Ming He, Xinchang Pang, Xueqin Liu, Beibei Jiang, Yanjie He, Henry Snaith, Zhiqun Lin

Abstract:

Extending the spectral absorption of organolead halide perovskite solar cells from visible into near-infrared (NIR) range renders the minimization of non-absorption loss of solar photons with improved energy alignment. Herein, we report on, for the first time, a viable strategy of capitalizing on judiciously synthesized monodisperse NaYF4 :Yb/Er upconversion nanoparticles (UCNPs) as the mesoporous electrode for CH3 NH3 PbI3 perovskite solar cells and more importantly confer perovskite solar cells to be operative under NIR light. Uniform NaYF4 :Yb/Er UCNPs are first crafted by employing rationally designed double hydrophilic star-like poly(acrylic acid)-block-poly(ethylene oxide) (PAA-b-PEO) diblock copolymer as nanoreactor, imparting the solubility of UCNPs and the tunability of film porosity during the manufacturing process. The subsequent incorporation of NaYF4 :Yb/Er UCNPs as the mesoporous electrode led to a high efficiency of 17.8 %, which was further increased to 18.1 % upon NIR irradiation. The in situ integration of upconversion materials as functional components of perovskite solar cells offers the expanded flexibility for engineering the device architecture and broadening the solar spectral use.

Photon recycling in lead iodide perovskite solar cells.

Science (New York, N.Y.) 351:6280 (2016) 1430-1433

Authors:

Luis M Pazos-Outón, Monika Szumilo, Robin Lamboll, Johannes M Richter, Micaela Crespo-Quesada, Mojtaba Abdi-Jalebi, Harry J Beeson, Milan Vrućinić, Mejd Alsari, Henry J Snaith, Bruno Ehrler, Richard H Friend, Felix Deschler

Abstract:

Lead-halide perovskites have emerged as high-performance photovoltaic materials. We mapped the propagation of photogenerated luminescence and charges from a local photoexcitation spot in thin films of lead tri-iodide perovskites. We observed light emission at distances of ≥50 micrometers and found that the peak of the internal photon spectrum red-shifts from 765 to ≥800 nanometers. We used a lateral-contact solar cell with selective electron- and hole-collecting contacts and observed that charge extraction for photoexcitation >50 micrometers away from the contacts arose from repeated recycling between photons and electron-hole pairs. Thus, energy transport is not limited by diffusive charge transport but can occur over long distances through multiple absorption-diffusion-emission events. This process creates high excitation densities within the perovskite layer and allows high open-circuit voltages.

Changes in mechanical and structural properties of Bi-2212 added MgB2 superconductors

Journal of Materials Science: Materials in Electronics Springer 27:6 (2016) 6060-6070

Authors:

E Taylan Koparan, B Savaskan, O Ozturk, S Kaya, C Aksoy, Junke Wang, Susannah C Speller, Christopher RM Grovenor, A Gencer, E Yanmaz

Abstract:

In the present study, we investigate the effects of Bi2Sr2Ca1Cu2O8+κ (Bi-2212) addition on structural and mechanical properties of bulk MgB2 obtained by hot-press method by means of X-ray diffraction, the Scanning Electron Microscopy and Vickers microhardness measurements. The amount of Bi-2212 was varied between 0 and 10 wt% (0, 2, 4, 6, 8 and 10 wt%) of the total MgB2. All samples were prepared by using elemental magnesium (Mg) powder, amorphous nano boron (B) powder and Bi-2212 powder which are produced by hot-press method. As a result of the hot-press process, the compact pellet samples were manufactured. The microhardness results were analyzed by Meyer’s law, Proportional Sample Resistance Model, Elastic–Plastic Deformation Model, Hays Kendall Approach, and Indentation Induced Cracking (IIC) Model. IIC model was identified as the most appropriate model for samples exhibiting the reverse indentation size effect behavior.