Nicolas Loones

Towards a better understanding of the use of additives in Zn(S,O,OH) deposition bath for high efficiency Cu(In,Ga)Se2-based solar cells

CBD-Zn(S,O,OH) remains one the most studied and promising Cd-free buffer layer for Cu(In,Ga)Se2-based solar cells, and has already demonstrated its potential to lead to high-efficiency solar cells. However Zn(S,O,OH) deposition time and metastable behavior of the final devices remain critical to outperform CdS-based devices. The aim of this work is to study and understand the influence of additives such as H2O2 on the deposition bath and on the surface of the absorber. These results will be related with final performances of the devices. A new promising additive, persulfate S2O82-, will be presented and could be the key to go beyond CdS-based solar cell records.

Search for new bath formulations Of Zn(S, O, OH) buffer layer to outperform record performances Of CdS-based CIGSe solar cells

Zn(S, O, OH) represents the most studied Cd-free material for replacing chemical bath deposited (CBD)-CdS buffer layers in Cu(In, Ga)Se2-based solar cells. However, the record performances remain lower than the CdS. The aim of this work is to study new bath compositions for CBD-Zn(S, O, OH), by introducing new complexing and non-complexing reactants for higher efficiencies, and to analyze their effects on growth mechanisms. Promising bath compositions based on the combined used of H2O2 and tri-sodium citrate have been developed, and could be a new avenue to outperform the CdS-based solar cells.

Highly efficient MoOx-free semitransparent perovskite cell for 4 T tandem application improving the efficiency of commercially-available Al-BSF silicon

In this work, the fabrication of MoOx-free semitransparent perovskite solar cells (PSC) with Power Conversion Efficiencies (PCE) up to 15.7% is reported. Firstly, opaque PSCs up to 19.7% were fabricated. Then, the rear metal contact was replaced by a highly transparent and conductive indium tin oxide (ITO) film, directly sputtered onto the hole selective layer, without any protective layer between Spiro-OMeTAD and rear ITO. To the best of our knowledge, this corresponds to the most efficient buffer layer-free semitransparent PSC ever reported. Using time-resolved photoluminescence (TRPL) technique on both sides of the semitransparent PSC, Spiro-OMeTAD/perovskite and perovskite/TiO2 interfaces were compared, confirming the great quality of Spiro-OMeTAD/perovskite interface, even after damage-less ITO sputtering, where degradation phenomena result less important than for perovskite/TiO2 one. Finally, a 4-terminal tandem was built combining semitransparent PSC with a commercially-available Aluminium Back Surface Field (Al-BSF) silicon wafer. That silicon wafer presents PCEu2009=u200919.52% (18.53% after being reduced to cell size), and 5.75% once filtered, to generate an overall 4u2009T tandem efficiency of 21.18% in combination with our champion large semitransparent PSC of 15.43%. It means an absolute increase of 1.66% over the original silicon wafer efficiency and a 2.65% over the cut Si cell.

Photochemical deposition of ZnS buffer layers for Cu(In, Ga)Se 2 thin film solar cells via reusable solutions

A new bath composition for ZnS buffer layer deposition is presented allowing its photochemical growth on CIGSe absorbers. The main advantages of this solution compared to classical CBD-Zn(S, O) bath are: the deposition occurs at room temperature, the concentration of chemical precursors is 10 times lower than classical CBD-Zn(S, O), the use of a complexing agent such as ammonia is avoided and the same bath can be reused for several depositions. The same bath can be re-used for at least 4 times, leading to efficiencies between 13 and 14%, which is similar to what is obtained with CdS-buffered references.A new bath composition for ZnS buffer layer deposition is presented allowing its photochemical growth on CIGSe absorbers. The main advantages of this solution compared to classical CBD-Zn(S,O) bath are: the deposition occurs at room temperature, the concentration of chemical precursors is 10 times lower than classical CBD-Zn(S,O), the use of a complexing agent such as ammonia is avoided and the same bath can be reused for several depositions. The same bath can be re-used for at least 4 times, leading to efficiencies between 13 and 14%, which is similar to what is obtained with CdS-buffered references.