Front passivation of Cu(In,Ga)Se2 solar cells using Al2O3: culprits and benefits

• Autor(a) principal: Curado, M. A.
• Data de Publicação: 2020
• Outros Autores: Teixeira, J. P., Monteiro, M., Ribeiro, E. F. M., Vilão, R.C., Alberto, H. V., Cunha, J. M. V., Lopes, T.S., Oliveira, K., Donzel-Gargand, O., Hultqvist, A., Calderon, S., Barreiros, M. A., Chiappim, W., Leitão, J. P., Silva, A. G., Prokscha, T., Vinhais, C., Fernandes, P. A., Salomé, P. M. P.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/30460
• topic: Surface passivation; Al2O3; Thin film solar cells; Atomic layer deposition (ALD); Cu(In,Ga)Se2 (CIGS)

In recent years, the strategies used to break the Cu(In,Ga)Se2 (CIGS) world record of light to power conversion efficiency, were based on improvements of the absorber optoelectronic and crystalline properties, mainly using complex post-deposition treatments. To reach even higher efficiency values, advances in the solar cell architecture are needed focusing in the CIGS interfaces. In this study, we evaluate the structural, morphological and optoelectronic impact on the CIGS properties of using an Al2O3 layer as a potential front passivation layer. The impact of Al2O3 tunnelling layer between CIGS and CdS is also addressed in this study. Morphological and structural analyses reveal that the use of Al2O3 alone is not detrimental to CIGS, although it does not resist to the CdS chemical bath deposition. When CdS is deposited on top of Al2O3, the CIGS optoelectronic properties are heavily degraded. Nonetheless, when Al2O3 is used alone, optoelectronic measurements reveal a positive impact of its inclusion such as a very low concentration of interface defects and the CIGS keeping the same recombination channels. With the findings of this study the best use of Al2O3 front passivation layer could be with alternative buffer layers. The Al2O3 layer will keep the CIGS surface with a low density of defects while keeping its structural and optoelectronic properties as good as the ones when CdS is deposited. It can also be reported that a comparison between the different analyses allowed us to strongly suggest for the first time that low-energy muon spin spectroscopy (LE-μSR) is sensitive to both charge carrier separation and bulk recombination in complex semiconductors.