DETERMINATION OF METALLIZATION-INDUCED RECOMBINATION CURRENT DENSITY FOR SILICON SOLAR CELLS

Date

2023-9-08

Author

ASLAN, Sercan

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The power conversion efficiency (PCE) of silicon (Si) solar cells decreases dramatically due to electron-hole recombinations. Recombination current density (J0) needs to be determined to elucidate electron-hole recombinations related to various fabrication steps (i.e., passivation and metallization). While the passivation quality of Si solar cells can be readily assessed by quasi-steady state photoconductance (QSSPC), the measurement of the recombination current density due to metallization (J0, m) is more challenging. In this thesis, J0, m values for Silver (Ag) together with Aluminium (Al) paste and J0, m values for Ag/Al paste and Ag paste of respective screen-print fabricated PERC and n-PERT solar cells were investigated. J0, m values were obtained for Ag paste using both photoconductivity decay (PCD) and Suns-Voc measurements using a metallization mask – designed in this work – that allows various metal fractions. Although both methods resulted in similar J0, m values, we utilized Suns-Voc measurements to measure the J0, m values for the other two pastes since the metallization paste must be etched using acid for PCD measurements. This is because, for the Suns-Voc measurements, it is sufficient if the ideal diode factor of the prepared cells is close to 1 with the appropriate firing method. In addition, based on the determined J0, m value of the Ag paste, the J0, m value of the Al paste was calculated for the same fabricated solar cell. Additionally, n- PERT Si solar cells were fabricated with three different boron doped emitters (peak concentration and junction depth) to investigate the J0, m value of the metal contact between the emitter and the Ag/Al paste by Suns-Voc measurements. Subsequently, all J0, m values (calculated and extracted from Suns-Voc measurements) of fabricated PERC and n- PERT cell types were confirmed by simulations to show the obtained J0, m values are reliable. Minimum J0, m values of 636, 1126, and 2123 fA/cm2 were obtained for Ag, Al, and Ag/Al pastes, respectively. This study shows that the J0, m value, which is crucial for improving the PCE of solar cells, can be reliably determined for three different metallization pastes and that the important influence of the doping profile on the recombination under metal contacts can be observed for n-PERT solar cells.

Subject Keywords

Metallization, Recombination, Metallization-Induced Recombination

URI

https://hdl.handle.net/11511/105509

Collections

Graduate School of Natural and Applied Sciences, Thesis