Solar cell characteristics determination

Patent metadata

Field	Value
Publication number	US-9389273-B2
Application number	US-201213675928-A
Country	US
Kind code	B2
Filing date	Nov 13, 2012
Priority date	Nov 13, 2012
Publication date	Jul 12, 2016
Grant date	Jul 12, 2016

Abstract

An apparatus for determining solar cell characteristics includes a quantum efficiency measurement tool configured to measure an external quantum efficiency of the solar cell and a reflectivity measurement tool configured to measure the reflectivity of the solar cell. The apparatus also includes a capacitance measurement tool configured to measure the capacitance of the solar cell and a processor configured to calculate a diffusion length of the solar cell based on the measured quantum efficiency, reflectivity and capacitance of the solar cell.

First claim

What is claimed is:

1. An apparatus for determining solar cell characteristics, comprising:
a light generator and sensor disposed to shine light on and detect light reflected from a solar cell;
a current meter disposed to detect current applied to the solar cell;
a power supply disposed to apply a bias voltage to the solar cell;
a quantum efficiency measurement tool configured to measure an external quantum efficiency (EQE) of the solar cell based on an intensity of light shined onto the solar cell and the detected applied current;
a reflectivity measurement tool configured to measure a reflectivity (R) of the solar cell based on an intensity of light shined onto and reflected from the solar cell;
a capacitance measurement tool comprising a capacitance meter configured to measure the capacitance (C) of the solar cell based on the voltage bias; and
a processor configured to:
calculate an internal quantum efficiency (IQE) of the solar cell based on the measured external quantum efficiency and the measured reflectivity using the following equation:

IQE
⁡

(
λ
)

=

EQE

1
-
R

,

wherein λ represents a wavelength at which the EQE and reflectivity are measured,
calculate a depletion width (x d ) of the solar cell using the measured capacitance using the following equation:
x d =∈A/C,

wherein ∈ represents a dielectric constant of an absorber layer of the solar cell and A represents an area of the solar cell,
determine a diffusion length (L d ) of the solar cell based on the calculated IQE and the calculated depletion width of the solar cell by curve-fitting IQE data using the following equation:

IQE
⁡

[

α
⁡

(
λ
)

,

x
d

⁡

(
V
)

,

L
d

]

=

1
-

1

1
+

α
⁡

(
λ
)

⁢

L
d

⁢

exp
⁡

[

-

α
⁡

(
λ
)

⁢

x
d

⁡

(
V
)

]

,

wherein α represents an absorption coefficient of the absorber layer of the solar cell and V represents a voltage bias applied to the solar cell.

2. The apparatus of claim 1 , wherein the processor is configured to control the quantum efficiency measurement tool to measure a plurality of external quantum efficiency values as a function of wavelengths and as a function of voltage biases, and to measure a plurality of reflectivity values as a function of wavelengths, to control the capacitance measurement tool to measure a plurality of capacitance values of the solar cell as a function of a plurality of voltage bias levels, to calculate a plurality of internal quantum efficiency values based on the plurality of external quantum efficiency values and reflectivity values, to calculate a plurality of depletion width values of the solar cell based on the plurality of capacitance values, and to calculate the diffusion length of the solar cell based on the plurality of internal quantum efficiency values and the plurality of depletion width values.

3. The apparatus of claim 2 , wherein the processor is further configured calculate the diffusion length of the solar cell by curve-fitting the plurality of internal quantum efficiency values and the plurality of depletion width values to calculate a single diffusion length value for the solar cell.

4. The apparatus of claim 2 , wherein the processor is further configured to calculate an absorption coefficient value of an absorber layer of the solar cell as a function of wavelength by curve-fitting the plurality of internal quantum efficiency values and the plurality of depletion width values.

5. The apparatus of claim 1 , wherein the apparatus is configured to maintain the solar cell in a same position and in connection with the EQE measurement tool, the reflectivity measurement tool, the light generator and sensor, the current meter, the power supply and the capacitance meter, and
wherein the apparatus further comprises a measurement tool controller configured to switch between measurements of the external quantum efficiency and reflectivity and the capacitance of the solar cell.

6. A non-transitory computer program product, comprising:
a tangible computer readable storage medium having stored therein a computer program including computer code which, when executed by a processor, controls a computer including the processor to perform a method, the method comprising:
shining light on and detecting light reflected from the solar cell at a light generator and sensor, detecting current applied to the solar cell at a current meter and applying a bias voltage to the solar cell by a power supply;
measuring an external quantum efficiency (EQE) of a solar cell based on

Assignees

• IBM

Inventors

• Gokmen Tayfun
• Gunawan Oki

Classifications

• H10F10/142

  comprising multiple PN homojunctions, e.g. tandem cells · CPC title

• H01L31/0687

  Electricity · mapped topic

• G01R31/2605 Primary

  Physics · mapped topic

• Y02E10/544

  Solar cells from Group III-V materials · CPC title

• Y02E10/50

  Photovoltaic [PV] energy · CPC title