In Situ LID and Regeneration of PERC Solar Cells from Different Positions of a B-Doped Cz-Si Ingot

<jats:p>In order to investigate the light-induced-degradation (LID) and regeneration of industrial PERC solar cells made from different positions of silicon wafers in a silicon ingot, five groups of silicon wafers were cut from a commercial solar-grade boron-doped Czochralski silicon (Cz-Si) ingot from top to bottom with a certain distance and made into PERC solar cells by using the standard industrial process after measuring lifetimes of minority carriers and concentrations of boron, oxygen, carbon, and transition metal impurities. Then, the changes of their <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M1"> <mi>I</mi> </math> </jats:inline-formula>-<jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M2"> <mi>V</mi> </math> </jats:inline-formula> characteristic parameters (efficiency <jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M3"> <mi>η</mi> </math> </jats:inline-formula>, open-circuit voltage <jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M4"> <msub> <mrow> <mi>V</mi> </mrow> <mrow> <mtext>oc</mtext> </mrow> </msub> </math> </jats:inline-formula>, short-circuit current <jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M5"> <msub> <mrow> <mi>I</mi> </mrow> <mrow> <mtext>sc</mtext> </mrow> </msub> </math> </jats:inline-formula>, and fill factor <jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M6"> <mtext>FF</mtext> </math> </jats:inline-formula>) with time were in situ measured by using a solar cell <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M7"> <mi>I</mi> </math> </jats:inline-formula>-<jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M8"> <mi>V</mi> </math> </jats:inline-formula> tester during the 1st LID (45°C, 1 sun, 12 h), regeneration (100°C, 1 sun, 24 h), and 2nd LID (45°C, 1 sun, 12 h). The results show that the LID and regeneration of the PERC solar cells are caused by the transition of B-O defects playing a dominant role together with the dissociation of Fe-B pairs playing a secondary role. The decay of <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M9"> <mi>η</mi> </math> </jats:inline-formula> during the 1st LID is caused by the degradation of <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M10"> <msub> <mrow> <mi>V</mi> </mrow> <mrow> <mtext>oc</mtext> </mrow> </msub> </math> </jats:inline-formula>, <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M11"> <msub> <mrow> <mi>I</mi> </mrow> <mrow> <mtext>sc</mtext> </mrow> </msub> </math> </jats:inline-formula>, and <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M12"> <mtext>FF</mtext> </math> </jats:inline-formula>, while the increase of <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M13"> <mi>η</mi> </math> </jats:inline-formula> during the regeneration is mainly contributed by <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M14"> <msub> <mrow> <mi>V</mi> </mrow> <mrow> <mtext>oc</mtext> </mrow> </msub> </math> </jats:inline-formula> and <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M15"> <mtext>FF</mtext> </math> </jats:inline-formula>, and the decay of <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M16"> <mi>η</mi> </math> </jats:inline-formula> during the 2nd LID is mainly induced by the degradation of <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M17"> <msub> <mrow> <mi>I</mi> </mrow> <mrow> <mtext>sc</mtext> </mrow> </msub> </math> </jats:inline-formula>. After regeneration, the decay rate of <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M18"> <mi>η</mi> </math> </jats:inline-formula> reduces from 4.43%–5.56% (relative) during the 1st LID to 0.33%–1.75% (relative) during the 2nd LID. </jats:p>