English: Cloze Test for Upcoming Exams – Set 163

Directions(1-10): In the passage given below there are 10 blanks. Every blank has four alternative words given in options (A),(B),(C), and (D). You have to tell which word is APPROPRIATE according to the context. If all are appropriate then mark your answer as “E”.

On the desk of Chris Case, chief technology officer of Oxford Photovoltaics, there sits a small but heavy vial filled with a canary-yellow liquid. “That’s enough for a kilowatt,” he says. The material in the ___1___ is called methylammonium lead iodide, and enthusiasts such as Dr Case believe it, and materials like it—known collectively as perovskites—could lead to a dramatic increase in the world’s use of power from the sun.
Oxford Photovoltaics is one of many firms, both small and large, that see ___2___ in perovskites. These are compounds that share a crystal structure and are named, collectively, after the mineral that was the first substance found to have this ___3___. Often, they are semiconductors. This means that, like the most famous semiconductor of all, silicon, they can be used in solar cells.
The first perovskite solar cells were made in 2009. They converted 3.8% of the light falling on them into electricity. Now, the best ___4___ around 20%. This rate of conversion is similar to the performance of commercial silicon cells, and researchers are confident they can push it to 25% in the next few years.
Moreover, unlike silicon, perovskites are cheap to turn into cells. To make a silicon cell, you have to slice a 200-micron-thick wafer from a solid block of the element. A perovskite cell can be made by mixing some chemical solutions and ___5___ the result onto a suitable backing, or by vaporising precursor molecules and letting them condense onto such a ___6___. If these processes can be commercialised, silicon solar cells will have a serious rival.
Solar cells, perovskite ones included, all function in broadly the same way. When light hits a crystal of the material they are made from, it frees electrons (which are negatively charged) and leaves behind what are, in effect, positively charged holes in the crystal lattice. This formation of electron-hole pairs is ___7___ of semiconductors exposed to light. Neighbouring materials then capture the positive and negative charges and ___8___ them to electrode layers on the cell’s outer faces, where they generate a current.
This general theme, though, is capable of variation. Last year, for example, Michael Grätzel of the Swiss Federal Institute of Technology, in Lausanne, devised a cell in which the perovskites were ___9___ into the electron-capturing material, rather than being a separate layer. That design, he thinks, will make cells cheaper to manufacture, and more stable. Dyesol, an Australian firm with which Dr Grätzel is collaborating, agrees. It is building a factory in Turkey, ___10___ to open in 2017, to manufacture solar cells that are based on the Grätzel infusion principle.

  1. beaker
    vessel
    vial
    ampule
    All are Correct
    Option E

     

  2. implore
    promise
    bloat
    appal
    All are Correct
    Option B

     

  3. structure
    chaos
    shambles
    bungle
    All are Correct
    Option A

     

  4. consumed
    tie up
    stuck up
    hoover up
    All are Correct
    Option E

     

  5. dripping
    drizzling
    pouring
    dribbling
    All are Correct
    Option C

     

  6. advancing
    backing
    aggression
    contrariety
    All are Correct
    Option B

     

  7. characteristic
    deviant
    cluster
    special
    All are Correct
    Option A

     

  8. bring
    convey
    transfer
    transport
    All are Correct
    Option D

     

  9. lordotic
    delves
    infused
    soused
    All are Correct
    Option C

     

  10. extemporized
    planned
    offhand
    fortuitous
    All are Correct
    Option B

     

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