Antisolvent Additive Spraying of Solar Cells

By Surbhi JainReviewed by Susha Cheriyedath, M.Sc.Mar 21 2022

In an article recently published in the journal ACS Applied Energy Materials, researchers discussed the synergetic effect of antisolvent additive spraying treatment and additive doping on the enhanced photovoltaic characteristics of spray-coated perovskite solar cells.

Study: Synergetic Effect on Enhanced Photovoltaic Performance of Spray-Coated Perovskite Solar Cells Enabled by Additive Doping and Antisolvent Additive Spraying Treatment. Image Credit: BELL KA PANG/Shutterstock.com

Background

The crystalline semiconductor known as organic-inorganic hybrid perovskite has sparked a lot of interest as a possible solar cell building material. Researchers are focused on developing effective manufacturing procedures for intensive production under ambient conditions in order to make the perovskite suitable for broad use.

The spray technique has been actively used to deposit active layers in perovskite solar cells, allowing for high-scale production. To improve the perovskite's photovoltaic performance and stability, charge recombination, thin-film morphologies, and defect densities must all be controlled. Additive engineering can effectively change film generation, perovskite crystal growth, and perovskite defect passivation.

Antisolvent dripping can be used to introduce non-fullerene organic semiconductors with functional cyano and carbonyl groups into perovskite films to decorate grain boundaries within the bulk film and passivate the trap states, resulting in improved stability and photovoltaic performance of the perovskite device. The spray-coated perovskite layer that passivates faults and improves performance is created by combining these two additive engineering processes.

About the Study

In this study, the authors investigated the antisolvent spraying treatment of methylammonium acetate (MAAc) additive doping in a perovskite precursor solution and a mixed non-fullerene small-molecule semiconductor additive (DCDTT) in chlorobenzene for the preparation of an ultrasonic spray-coated perovskite film. Through additive engineering, this spray-coating approach was used to create densely packed crystals and to passivate the defect states found around the surface grain boundaries.

The team illustrated the addition of MAAc to perovskite films, together with the antisolvent DCDTT treatment, to improve crystallinity and minimize trap states and grain boundaries. These findings suggest that adding additives to a scalable spraying approach for producing perovskite films has a passivating impact.

The researchers described the incorporation of a MAAc additive in the perovskite precursor solution and a non-fullerene fused ring dicyclopentadithienothiophene-derived small molecule DCDTT as an additive in the anti-solvent step for the ambient preparation of a perovskite film by using an ultrasonic spray-coating method.

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The additions were used to increase crystallinity, make charge transport more efficient, lower defect density, and charge recombination. At the start of the spray coating process, MAAc was added to the precursor solution to create the methylammonium lead iodide (MAPbI₃) perovskite. Second, during the post-spraying treatment, the semiconducting DCDTT small molecule was introduced to the antisolvent step.

The authors used Vilsmeier-Haack conditions to treat the fused thiophene core with POCl₃ for the production of an intermediate aldehyde. Knoevenagel condensation of the resultant aldehyde with 2-(5,6-dichloro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile yielded DCDTT. The chemical characteristics of the target DCDTT and its corresponding intermediate were studied using ¹³C NMR, ¹H NMR, and mass spectroscopy. Surface morphologies and device performance were investigated in relation to organic ammonium non-halide salts such as MAAc-containing precursors. Top-view scanning electron microscopy (SEM) was used to examine the surface topographies of the MAAc-doped and control MAPbI₃ perovskite films.

Observations

The equivalent inverted perovskite solar cell had a significantly greater power conversion efficiency (PCE) of 17.18% than the control device, which had a PCE of 10.04%. After seven days in ambient circumstances, the synergetic additive-modified perovskite devices retained 85% of their initial PCE.

After exposure to 30-40% relative humidity at ambient temperature for seven days, the inverted structured perovskite solar cell treated with MAAc and DCDTT additives obtained a substantially better power conversion efficiency (PCE) than the control device and lost 15% PCE. The proposed device's acquired PCE was found to be one of the highest among spray-coated MAPbI₃-based planar perovskite solar cells.

The additions increased the film quality of the MAPbI₃ perovskite by forming a MAAc-based intermediate and a DCDTT coordination interaction with Pb²⁺. The optimized device had a PCE of 17.18% when MAAc and DCDTT of 2 mg ml^-1 concentration were used in chlorobenzene. Furthermore, after seven days of storage in ambient settings, the environmental stability of the unsealed optimized device remained 85% of its original PCE. The proposed two-step additive-treated technique increased device performance in inverted planar perovskite solar cells. These two methods worked together to create a homogeneous perovskite layer with larger grain size, increased crystallinity, and defect passivation.

Conclusions

In conclusion, this study elucidated the importance of the synergistic additive effect provided by precursor stoichiometry and anti-solvent treatment on perovskite film spray deposition for developing an efficient and stable solar system.

The authors observed that the combined actions of the two compounds had a positive impact on perovskite solar cells' photovoltaic performance and stability. They also believe that when adopting a scalable spray coating manufacturing method, this work can be used as a reference for additive engineering to produce a high PCE and stability.

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