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GATE 2020 EC – Question 44

Electronic Devices · P-N Junction and Semiconductor Devices · 2 marks · Multiple choice

A $pn$ junction solar cell of area 1.0 cm$^2$, illuminated uniformly with 100 mW cm$^{-2}$, has the following parameters: Efficiency $=15\%$, open circuit voltage $=0.7$ V, fill factor $=0.8$, and thickness $=200\ \mu$m. The charge of an electron is $1.6\times10^{-19}$ C. The average optical generation rate (in cm$^{-3}$s$^{-1}$) is

  1. $0.84\times10^{19}$.
  2. $5.57\times10^{19}$.
  3. $1.04\times10^{19}$.
  4. $83.60\times10^{19}$.

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Show answer and explanation

Correct answer: (A) $0.84\times10^{19}$.

Explanation

The output power is $0.15\times100\text{ mW}=15$ mW $=V_{oc}I_{sc}\,FF$, so $I_{sc}=\frac{15\text{ mW}}{0.7\times0.8}=26.8$ mA. The generation rate is $G=\frac{I_{sc}}{q\,A\,t}=\frac{26.8\times10^{-3}}{1.6\times10^{-19}\times1\times200\times10^{-4}}=8.4\times10^{18}=0.84\times10^{19}\ \text{cm}^{-3}\text{s}^{-1}$.