Thermomechanical Lift-Off and Recontacting of CdTe Solar Cells.

Controlled delamination of thin-film photovoltaics (PV) post-growth can reveal interfaces that are critical to device performance yet are poorly understood because of their inaccessibility within the device stack. In this work, we demonstrate a technique to lift off thin-film solar cells from their glass substrates in a clean, reproducible manner by first laminating a polymeric backsheet to the device and then thermally shocking the system at low temperatures ( T ≤ -30 °C). To enable clean delamination of diverse thin-film architectures, a theoretical framework is developed and key process control parameters are identified.

Internal sensor compensation for increased Ca test sensitivity.

The development of state-of-the-art barrier films and encapsulation schema for displays and photovoltaics requires precise measurement of water vapor permeation as quickly as possible. We have demonstrated improvements to our electrical, Ca-trace-based water vapor transmission rate measurement technique without introducing any additional cost or sample handling concerns. Most importantly, the contacting scheme was changed so that the effective length of the sensor traces can be more precisely determined making the contact resistance between the Ca and Au/Ti films far less likely to affect the results.

Evaluation of the sensitivity limits of water vapor transmission rate measurements using electrical calcium test.

The development of flexible organic light emitting diode displays and flexible thin film photovoltaic devices is dependent on the use of flexible, low-cost, optically transparent and durable barriers to moisture and∕or oxygen. It is estimated that this will require high barriers with water vapor transmission rates (WVTR) between 10(-4) and 10(-6) g∕m(2)∕day. Thus, there is a need to develop a relatively fast, low cost, and quantitative method to evaluate such low permeation rates.

Quantitative calcium resistivity based method for accurate and scalable water vapor transmission rate measurement.

The development of flexible organic light emitting diode displays and flexible thin film photovoltaic devices is dependent on the use of flexible, low-cost, optically transparent and durable barriers to moisture and/or oxygen. It is estimated that this will require high moisture barriers with water vapor transmission rates (WVTR) between 10(-4) and 10(-6) g/m(2)/day. Thus there is a need to develop a relatively fast, low-cost, and quantitative method to evaluate such low permeation rates.

Rheological study of structural transitions in triblock copolymers in a liquid crystal solvent.

Rheological properties of triblock copolymers dissolved in a nematic liquid crystal (LC) solvent demonstrate that their microphase separated structure is heavily influenced by changes in LC order. Nematic gels were created by swelling a well-defined, high molecular weight ABA block copolymer with the small-molecule nematic LC solvent 4-pentyl-4'-cyanobiphenyl (5CB). The "B" midblock is a side-group liquid crystal polymer (SGLCP) designed to be soluble in 5CB and the "A" endblocks are polystyrene, which is LC-phobic and microphase separates to produce a physically cross-linked, thermoreversible, macroscopic polymer network.

Self-assembled liquid-crystalline gels designed from the bottom up.

Liquid crystals are often combined with polymers to influence the liquid crystals' orientation and mechanical properties, but at the expense of reorientation speed or uniformity of alignment. We introduce a new method to create self-assembled nematic liquid-crystal gels using an ABA triblock copolymer with a side-group liquid-crystalline midblock and liquid-crystal-phobic endblocks. In contrast to in situ polymerized networks, these physical gels are homogeneous systems with a solubilized polymer network giving them exceptional optical uniformity and well-defined crosslink density.