Unveiling the impact of Cu content on the physical properties and photovoltaic performance of solution‐processed Cu(In,Ga)Se2 solar cell absorber

• Published in: International journal of energy research Vol. 45; no. 5; pp. 6966 - 6984
• Main Authors: Marasamy, Latha, Rasu Chettiar, Aruna‐Devi, Moure‐Flores, Francisco, Subramaniam, Velumani
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Inc 01.04.2021; Hindawi Limited
• Subjects: Absorbers; Carrier density; Cell size; chalcogenide semiconductor; chalcopyrite absorber; Copper; Copper indium gallium selenides; Cost analysis; Crystal growth; Crystals; Cu(In,Ga)Se2 solar cell; Diameters; Electrical properties; Energy conversion; Energy conversion efficiency; Nucleation; Photoelectric effect; Photoelectric emission; Photovoltaic cells; Photovoltaics; Physical properties; Shape; Solar cells; Solar energy; Solar energy conversion; Solar power; solution process; Structural analysis; Thickness; Unit cell
• ISSN: 0363-907X; 1099-114X
• DOI: 10.1002/er.6285

Summary Cu/Ga + In (CGI) ratio in Cu(In,Ga)Se2 (CIGSe) semiconductor plays a decisive role in solar energy conversion. Investigations published so far relevant to CIGSe at different CGI values are solely based on the expensive vacuum process and as a result, there is a strong urge to explore a low‐cost process. In this regard, we herein report the preparation of CIGSe at diverse CGI value from 0.70 to 0.97 by a facile and cost‐effective solution process for the first time. From structural analysis, the blue shift is perceived by decreasing CGI value, which is related to shrinkage in the unit cell volume because of the reduction in the Cu content. As CGI value increases, crystal diameter of CIGSe vastly changed from nano to micro (50‐1300 nm), whereas crystal shape reformed from irregular to hexagonal flake‐like shape, which could be due to excessive influence of Cu content that alters nucleation and growth of crystals. Diverse CGI value modified Se/(Cu + In + Ga) ratio while Ga/(Ga + In) ratio remains unchanged. Bandgap energy is increased from 1.22 to 1.41 eV as Cu‐deficiency increases. The morphological analysis showed a uniform, smooth and crack‐free CIGSe films with a thickness of ~1 μm. The electrical properties of CIGSe are greatly changed. For instance, at higher CGI value (0.97), the carrier concentration is increased by five‐order magnitude, whereas mobility improved by 109 times and resistivity decreased by 87 times as compared to lower CGI value (0.70). Moreover, photocurrent is markedly enhanced by six‐order magnitude explicitly from nA to mA. As a proof of concept, solar cells are fabricated and power conversion efficiency significantly enhanced from 0.16% to 3.38% by altering CGI value. Hence, this work eminently evidences the importance of tuning CGI value by low‐cost solution process and provides new perceptions into properties of CIGSe solar cell absorber as a function of CGI value. We demonstrate the effective synthesis of CIGSe absorber at diverse CGI value via a simple and low‐cost solution process for the first time. Besides, we explored various properties of CIGSe as a function of CGI value. As a concluding remark, the power conversion efficiency of CIGSe thin film solar cells was significantly improved from 0.16 to 3.38% by altering CGI value.