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Concept: IBM


Morphology control of solution coated solar cell materials presents a key challenge limiting their device performance and commercial viability. Here we present a new concept for controlling phase separation during solution printing using an all-polymer bulk heterojunction solar cell as a model system. The key aspect of our method lies in the design of fluid flow using a microstructured printing blade, on the basis of the hypothesis of flow-induced polymer crystallization. Our flow design resulted in a ∼90% increase in the donor thin film crystallinity and reduced microphase separated donor and acceptor domain sizes. The improved morphology enhanced all metrics of solar cell device performance across various printing conditions, specifically leading to higher short-circuit current, fill factor, open circuit voltage and significantly reduced device-to-device variation. We expect our design concept to have broad applications beyond all-polymer solar cells because of its simplicity and versatility.

Concepts: Fluid dynamics, Solar cell, Photovoltaics, Direct current, Fill factor, IBM, P-n junction, Solar cells


This article critically examines the corporate production, archival politics, and socio-legal dimensions of Corporate Mortality Files (CMFs), the largest corporate archive developed by International Business Machine’s Corporation (IBM) to systematically document industrial exposures and occupational health outcomes for electronics workers. I first provide a history of IBM’s CMF project, which amounts to a comprehensive mortality record for IBM employees over the past 40 years. Next, I explore a recent case in Endicott, New York, birthplace of IBM, where the U.S. National Institute for Occupational Safety and Health (NIOSH) studied IBM’s CMFs for workers at IBM’s former Endicott plant. Tracking the production of the IBM CMF, the strategic avoidance of this source of Big Data as evidence for determining a recent legal settlement, alongside local critiques of the IBM CMF project, the article develops what I call “late industrial necropolitics.” This article is protected by copyright. All rights reserved.

Concepts: Law, All rights reserved, Occupational safety and health, IBM, Copyright, Endicott, New York, Computing Tabulating Recording Corporation, Binghamton, New York


Significant photocurrent enhancement has been demonstrated using plasmonic light-trapping structures comprising nanostructured metallic features at the rear of the cell. These structures have conversely been identified as suffering heightened parasitic absorption into the metal at certain resonant wavelengths severely mitigating benefits of light trapping. In this study, we undertook simulations exploring the relationship between enhanced absorption into the solar cell, and parasitic losses in the metal. These simulations reveal that resonant wavelengths associated with high parasitic losses in the metal could also be associated with high absorption enhancement in the solar cell. We identify mechanisms linking these parasitic losses and absorption enhancements, but found that by ensuring correct design, the light trapping structures will have a positive impact on the overall solar cell performance. Our results clearly show that the large angle scattering provided by the plasmonic nanostructures is the reason for the enhanced absorption observed in the solar cells.

Concepts: Light, Photoelectric effect, Cadmium, Solar cell, Absorption, Photovoltaics, IBM


Advances in computational materials have paved a way to design efficient solar cells by identifying the optimal properties of the device layers. Conventionally, the device optimization has been governed by single or double descriptors for an individual layer; mostly the absorbing layer. However, the performance of the device depends collectively on all the properties of the material and the geometry of each layer in the cell. To address this issue of multi-property optimization and to avoid the paradigm of reoccurring materials in the solar cell field, a full space material-independent optimization approach is developed and presented in this paper. The method is employed to obtain an optimized material data set for maximum efficiency and for targeted functionality for each layer. To ensure the robustness of the method, two cases are studied; namely perovskite solar cells device optimization and cadmium-free CIGS solar cell. The implementation determines the desirable optoelectronic properties of transport mediums and contacts that can maximize the efficiency for both cases. The resulted data sets of material properties can be matched with those in materials databases or by further microscopic material design. Moreover, the presented multi-property optimization framework can be extended to design any solid-state device.

Concepts: Solar cell, Germanium, Photodiode, Maxima and minima, Copper indium gallium selenide, IBM, Solid state


We present here a symmetrically structured bifacial solar cell tailored by two fluorescent photoanodes and a platinum/titanium/platinum counter electrode, yielding extra-high short-circuit current densities as high as 28.59 mA cm(-2) and 119.9 μA cm(-2) in simulated sunlight irradiation (100 mW cm(-2), AM1.5) and dark-light conditions, respectively.

Concepts: Cadmium, Solar cell, Photovoltaics, Battery, Electrode, Diode, IBM


We found that elemental Si-doped Cu(In,Ga)Se2 (CIGS) polycrystalline thin films exhibit a distinctive morphology due to the formation of grain boundary layers several tens of nanometers thick. The use of Si-doped CIGS films as the photoabsorber layer in simplified structure buffer-free solar cell devices is found to be effective in enhancing energy conversion efficiency. The grain boundary layers formed in Si-doped CIGS films are expected to play an important role in passivating CIGS grain interfaces and improving carrier transport. The simplified structure solar cells, which nominally consist of only a CIGS photoabsorber layer and a front transparent and a back metal electrode layer, demonstrate practical application level solar cell efficiencies exceeding 15%. To date, the cell efficiencies demonstrated from this type of device have remained relatively low, with values of about 10%. Also, Si-doped CIGS solar cell devices exhibit similar properties to those of CIGS devices fabricated with post deposition alkali halide treatments such as KF or RbF, techniques known to boost CIGS device performance. The results obtained offer a new approach based on a new concept to control grain boundaries in polycrystalline CIGS and other polycrystalline chalcogenide materials for better device performance.

Concepts: Solar cell, Photovoltaics, Energy conversion, Energy conversion efficiency, Diode, Copper indium gallium selenide, IBM


The aim of this study was to compare the accuracy of the oscillating tip saw system (Precision Saw=PS) with the more conventional fully oscillating blade system (Sagittal Saw=SS) during computer-assisted total knee arthroplasty (CAS-TKA).

Concepts: Clinical trial,, Accuracy and precision, Knee replacement, Flexion, IBM


We utilise spray-coating under ambient conditions to sequentially deposit compact-TiO2, mesoporous-TiO2, CH3NH3PbI(3-x)Clx perovskite and doped spiro-OMeTAD layers, creating a mesoporous standard architecture perovskite solar cell (PSC). The devices created had an average power conversion efficiency (PCE) of 9.2% and a peak PCE of 10.2%; values that compare favourably with control-devices fabricated by spin-casting that had an average efficiency of 11.4%. We show that our process can be used to create devices having an active-area of 1.5 cm(2) having an independently verified efficiency of 6.6%. This work demonstrates the versatility of spray-coating as well as its potential as a method of manufacturing low-cost, large-area, efficient perovskite devices.

Concepts: Energy, Solar cell, Photovoltaics, Energy conversion, Energy conversion efficiency, 2006 albums, IBM, P-n junction


Two arylamine-based hole transporting materials with an anthracene π-linker have been synthesized and tested for perovskite solar cells. Improved power conversion efficiency and stability were achieved by employing A102 compared with that of spiro-OMeTAD.

Concepts: Solar cell, Energy conversion, Energy conversion efficiency, IBM


Organo metal halide perovskites have emerged as highly promising replacements for thin film solar cells. However, their poor stability under ambient conditions remains problematic, hindering commercial exploitation. Here, we describe our investigation on the incorporation of a fluorous-functionalized imidazolium cation in a highly stable cesium based mixed perovskite material (Cs0.05(MA0.15FA0.85)0.95Pb(I0.85Br0.15)3 and how it influnce enhances stability. The resulting materials, which vary according to the content of the fluorous-functionalized imidazolium cation, display a prolonged tolerance to atmospheric humidity (>100 days) along with power conversion efficiencies exceeding 16%. This work provides a general route which can be implemented in variety of perovskites and highlights a promising way to increase perovskite solar cell stability.

Concepts: Solar cell, Photovoltaics, Energy conversion, Energy conversion efficiency, Thin film solar cell, IBM