122-123 The working principle of solar cells
Author: Source: Datetime: 2017-01-23 18:01:11
220.127.116.11 The working principle of solar cells
5-4 solar spectral wavelength / μm
(Dotted line is 5762K blackbody radiation spectrum, dotted line is the spectrum of atmospheric mass 0, solid line is the spectrum of atmospheric mass 2)
Figure 5-5 single-crystal silicon at room temperature and a light absorption coefficient of the depth of light XL
Since light is absorbed in the material, F (λ, x) becomes smaller as x increases. That is, there are the following relations:
According to Eqs. (5-1) and (5-2), the formula for G (λ, x) is:
In the formula, F0 (λ) is the luminous flux of the incident surface.
As shown in Figure 5-4, when the incident light flux is continuous spectrum, the formula (5-3) is the carrier generation rate G (λ)
In the formula, F0(λ) is the luminous flux of the incident surface.
As shown in Figure 5-4, when the incident light flux is continuous spectrum, the formula (5-3) is the carrier generation rate G(λ)
Here, for the sake of simplicity, it is assumed that a (λ) Does not change in the depth direction of the material, nor is the absorption of free carriers.
If the excess carriers due to the light absorption can be taken out from the outside of the battery, it is preferable, but in the actual recombination process, the excess carriers are lost. For example, in a P-type semiconductor bulk body, the carrier recombination ratio R is affected by a change in the state of thermal balance of the number of carriers. Consider the following three items can be drawn from the following formula:
R=A(n 一n0)+B(Pn-P0n0)+Cp(p2n—p20n0)+Cn(Pn2—p0n20) (5-5)
P0、n0 are the concentrations of holes and electrons, respectively, which can be denoted as p = p0 + Δp, n = n0 + Δn (Δp, Δ), where p0 and n0 are the concentration of holes and electrons, respectively. N are the concentrations of excess holes and excess electrons, respectively, Δp = Δn) when the carriers are not captured. Substituting this relationship into equation (5-5), taking into account that it is a p-type semiconductor (p0≫N0)
R=A∆n + B(p0+n0+∆n)∆n+Cp(P20+2p0∆n+∆n2 )∆n+Cn(n20+2n0△n+∆n2)∆n (5-6)
The first term in the formula (5-6) is the recombination of the defect, the second is the radiative recombination, the third and the fourth terms show that the sample with higher concentration (1018cm-3) (Fig. 5-6) in the form of excitation heat (phonon), light, and second carrier, respectively, when the number of carriers is large. In addition, with the recombination, the third term of Equations (5-5) and (5-6) corresponds to the excitation of holes in the valence band, and the fourth term corresponds to the excitation of electrons in the conduction band. Working at room temperature above the crystalline silicon solar cell composite process is the first through the defects between the composite and the third, the fourth of the Auger recombination. The composite life is defined as τr
τ= 1/A = [τp (n0+ n1+∆n) +τn (p0+p1+ ∆n)]/(p0+n0+ ∆n) (5-8)
Here are given τp, τn, p1, p2 formula:
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