A comprehensive analysis of recombination at grain boundaries in high-efficiency kesterite-type solar cells
The present work reports on microscopic analyses of recombination at grain boundaries (GBs) in polycrystalline Li-doped (Ag,Cu)2ZnSn(S,Se)4 (Li-ACZTSSe) and Cu2ZnSnS4 (CZTS) absorber layers in high-efficiency solar cells (conversion efficiencies of 14.4% and 10.8%). Recombination velocities sGB were...
| Autores: | , , , , , , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/443527 |
| Acceso en línea: | https://hdl.handle.net/2117/443527 https://dx.doi.org/10.1002/eem2.70048 |
| Access Level: | acceso abierto |
| Palabra clave: | Cathodoluminescence Grain boundaries Kesterite Recombination velocity Solar cells Àrees temàtiques de la UPC::Energies::Energia solar fotovoltaica::Cèl·lules solars |
| Sumario: | The present work reports on microscopic analyses of recombination at grain boundaries (GBs) in polycrystalline Li-doped (Ag,Cu)2ZnSn(S,Se)4 (Li-ACZTSSe) and Cu2ZnSnS4 (CZTS) absorber layers in high-efficiency solar cells (conversion efficiencies of 14.4% and 10.8%). Recombination velocities sGB were determined at a large number of GBs by evaluating profiles extracted from cathodoluminescence intensity distributions across GBs in these polycrystalline layers. In both Li-ACZTSSe and CZTS absorber layers, the sGB values exhibited wide ranges over several orders of magnitude with a median values of 680 and 1100¿cm¿s-1 for the Li-ACZTSSe and CZTS absorbers. A model that provides a comprehensive explanation for this finding is presented and discussed in detail. Correspondingly, wide ranges for sGB can be explained by different positive or negative excess charge densities present at different GBs, leading to different downward or upward band bending on the order of several ±10¿meV, provided that the net-doping density of the absorber layers is sufficiently large. As a result of the evaluation of the sGB, input parameters for multidimensional device simulations are obtained. It is revealed that the grain boundary lifetime closely matches the overall effective lifetime, indicating that grain boundary recombination is a key factor limiting the effective carrier lifetime of both Li-ACZTSSe and CZTS absorbers. The estimated VOC losses due to GBs reach up to 126¿mV for Li-ACZTSSe and 88¿mV for CZTS. This work highlights that reducing grain boundary recombination via improved passivation and increasing grain size is an effective strategy for achieving further efficiency improvements. |
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