NENG 421 Solar Cells and Nanotechnology

HW#5 Spring 2015

First Name: Miguel Last Name: Ramirez

Answer the following questions, justify your answer. All questions are of equivalent points. Total HW points: 100. Due in May 1 st , 2015

Exercise 7.1

(a) Provide a schematic representation of the chalcopyrite CIS structure (drawn with In), and CZTS kesterite and stannite structures (drawn with Zn, andSn).

(b) Identify the unit cell boundaries and the space group for each structural type (Reference your source)

For the Chalcopyrite unit cell boundaries:1. a = 5.289 Å2. c = 10.423 Å3. Z = 4

For the Kesterite unit cell boundaries:1. a = 5.427 Å2. c = 10.871 Å3. Z = 2

For the Stannite unit cell boundaries:1. a = 5.4432 Å2. c = 10.7299 Å3. Z=2

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Exercise 7.2

Describe a non-vacuum deposition method of CZTS and any deposition (vacuum or non vacuum) method of SnS.

For CZTS:

(i) solution-based precursor fabrication followed by a short annealing, (ii) annealing of nano-crystalline precursors, (iii) low-temperature co-evaporation followed by a short annealing, (iv) sputter deposition followed by long annealing in H2S, and (v) fast co-evaporation (Redinger et al., 2011; Riha et al., 2009). One interesting fact regarding the processing of CZTS is that a non-vacuum based processing scheme is still leading to highest efficiencies, even though very recently Repins and co-workers published a 9.15% efficient CZTS based solar cell fabricated by vacuum-based 4- source co-evaporation, stating that the ease of composition and phase control is responsible for the success of the solution based processes (Katagiri et al., 1997).

This comes from this source:

http://ac.els-cdn.com/S0038092X1300159X/1-s2.0-S0038092X1300159X-main.pdf?_tid=7c4aab36-f021-11e4-91e4-00000aacb35f&acdnat=1430498913_044caa5878f8a5c2dd069be3685dd166

For SnS:

1. Metallic tin precursor layers of 300 nm were deposited on ultrasonically cleaned Mo-coated soda lime glass substrate by DC magnetron sputtering process using VRSU048 sputtering system (4N Tin target Kurt J. Lesker).

2. Tin precursors were sulphurized by a sulphurization system3. The tin layers were kept inside a graphite box together with 99.998% pure sulphur flakes

(Sigma Aldrich) and then placed onto the heater in the closed chamber.4. Sulphurization was performed in the temperature range of 150-450o C for a fixed time

period of 120 min and then the films were allowed to cool down naturally to room temperature

5. Thickness is then varied as you change the temperature, higher temperatures yield thicker material

This information came from this source:

http://ac.els-cdn.com/S1567173915000310/1-s2.0-S1567173915000310-main.pdf?_tid=4b1c3eac-f022-11e4-86e5-00000aacb35e&acdnat=1430499260_7d5a842416e9b035271b8a819ed6f1de

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