Shows the external quantum efficiency (EQE) of a solar cell...

Shows the external quantum efficiency (EQE) of a solar cell as a function of the wavelength under short circuit condition $(V=0 \mathrm{~V})$. (a) What is the bandgap (in $\mathrm{eV}$ ) of the absorber layer of the solar cell? (b) Calculate the short circuit current density $J_{\mathrm{sc}}$ of the solar cell for the wavelength range of $300-1300 \mathrm{~nm}$, if the incident (total) photon flux for this wavelength range is $\Phi_{\mathrm{ph}}=4.05 \times 10^{21} \mathrm{~m}^{-2} \mathrm{~s}^{-1}$.

Shows the external quantum efficiency (EQE) of a solar cell as a function of the wavelength under short circuit condition $(V=0 \mathrm{~V})$.
(a) What is the bandgap (in $\mathrm{eV}$ ) of the absorber layer of the solar cell?
(b) Calculate the short circuit current density $J_{\mathrm{sc}}$ of the solar cell for the wavelength range of $300-1300 \mathrm{~nm}$, if the incident (total) photon flux for this wavelength range is $\Phi_{\mathrm{ph}}=4.05 \times 10^{21} \mathrm{~m}^{-2} \mathrm{~s}^{-1}$.

Key Concepts

Short Circuit Current Density (Jsc)

Short circuit current density is the current produced per unit area when the solar cell’s output terminals are shorted (zero voltage condition). It is determined by integrating the product of the photon flux and the quantum efficiency over the range of wavelengths where absorption occurs, representing the maximal light-generated current the device can deliver.

Photon Flux

Photon flux refers to the number of photons incident on a surface per unit area per unit time. It is a critical parameter for calculating the photocurrent in a solar cell since the rate of photon arrival, in combination with the quantum efficiency, dictates the generation rate of electron–hole pairs.

Wavelength-Photon Energy Relationship

The relationship between the wavelength of light and the energy of its photons is given by the equation E = hc/?, where h is Planck’s constant and c is the speed of light. This fundamental concept is used to convert between the wavelength domain and the energy domain, which is crucial for identifying the bandgap from spectral absorption data.

External Quantum Efficiency (EQE)

EQE describes the fraction of incident photons that are converted into electrical charge carriers and collected by the solar cell. It is a key parameter in evaluating the performance of photovoltaic devices because it directly relates the optical input (photons of various wavelengths) to the electrical output (current).

Bandgap

The bandgap is the minimum energy required to excite an electron from the valence band to the conduction band in a semiconductor. It determines the spectral range of photons that can be absorbed by the material, with photons having energy equal to or greater than the bandgap contributing to charge carrier generation.

Transcript

00:01 Alright guys, let's focus on question 1 first.

00:04 Okay, so we know the intensity of such cell, solar cell, is 800 watts per meter square.

00:12 Okay, and the average is 0 .2 0 .20 times 0 .20, which is 0 .04 meters square.

00:21 The wavelength is 500 nanometer, okay? and we know the total energy of the photon is nhf.

00:29 And nhf can be equal to nh times c of landa, which will give us n equal to e times lambda divided by hc, okay? which will give us pt landa divide by hc, which is p, sorry, which is iat landa divide by hc.

01:06 Okay, so the p t here is the is equal to the energy because p is the power t is the time and powers the energy per time okay so it's p t and p t can be equal to i a which is intensity times the area okay so which can give us iat so leave the rest the same which landa and divide by hc so n equal to i a t londa divide by hc which will give us i is 800 watts per meter square times a which is 0 .04 meter square times t which is so usually we're talking about geo per second so let's say one second okay so t is equal to one second and the landa is 500 nanometer which is 500 times 10 to negative 9 meter because one nanometer is 10 to negative 9 meter h is 6 .63 times 10 to the power of negative 34, geo times second times the speed of light, which is 3 times 10 to the power of 8 meter per second.

02:32 This will give us the number of the h photons that will emit it is a .0 times 10 to the power of 19.

02:43 Okay.

02:45 Question b was asking us what is the, let me see, what is the, what is the, what what is the maximum possible currents that will be formed by this process.

02:59 Well, we know the current, which is a, sorry, which is i, that's for current, that it represents current, is equal to q, divided by t.

03:14 Okay, q is the total charge, t is the time.

03:19 Usually we're talking about one second here because it usually means the total amount of charge per second.

03:24 So now we know q, because we know the total number of photons is 8 .0 times 10 to the power of 19.

03:37 Okay.

03:41 And each photon, which means each electron has a charge of 1 .6 times 10 to the power of 19 cullons.

03:52 Okay.

03:54 That's the coolant.

03:55 That's the charge for each electron or each photon.

03:58 Time, okay, and times one second.

04:02 Okay, i'm sorry, it's 10 to negative 19, my bay.

04:05 So that will give us i equal to 12 .8 ampere...

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