Scalable Precursor Solution for Stable Perovskite Solar Cells: From Solutions to High-quality Films
Manuel Vasquez-Montoya a, Daniel Ramirez a, Juan F Montoya a, Franklin Jaramillo a
a Centro de Investigación, Innovación y Desarrollo de Materiales – CIDEMAT, Universidad de Antioquia UdeA, Calle 70 No 52-21, Medellín, Zip Code 1226
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Poster, Manuel Vasquez-Montoya, 245
Publication date: 11th February 2019

Hybrid halide perovskites processed from methylamine and acetonitrile solvents have attracted great attention due to their capacity to achieve uniform and crystalline films leading to highly efficient devices in a single-step deposition method [1]. Its inherent fast film crystallization facilitates its application to continuous printing methods compatible with roll-to-roll processing[2]. Moreover, this precursor have also demonstrated a remarkable stability, achieving over 2000 h of operation under real outdoor exposure conditions in 17cm2 modules [3]. Despite this excellent properties, this method uses MAPbI3 perovskite, which suffers a premature degradation associated to heat and moisture, hindering their long-term stability.

On the look for other compositions, it has been proved that methylamine gas forms a liquid state phase in other perovskite structures like FAPbI3 [4] , CsPbI3 [5] , BA2PbI3 [6], among others. A swelling in the structure is observed. Such fact is attributed to the slicing of 3D structure on low dimensional layers[7]. However, it remains still unclear what happens on mixed compositions. In addition, no attention has been paid in the acetonitrile role in the solution, and their implementation has been limited to empirically approach. This lack of understanding limits its application to more complex compositions potentially leading to higher device stability and efficiency. 

In this work, we explore the role of the low boiling point solvent in the solubility of the perovskite and how to apply this understanding to achieve solutions and films of mixed composition perovskites. We found that acetonitrile solvent is not mandatory to solubilize methylamine liquid phase, instead, good quality MAPbI3 could be obtained using protic solvents like ethanol. Nonetheless, these solutions are unstable, forming precipitates after an hour. To avoid this problem, a mixture of acetonitrile-ethanol was implemented, successfully diluting the liquid phase of MAPbI3 and MAPbBr3 without forming a precipitate. Motivated with those results, more complex structures like (MA0.2FA0.8)Pb(I0.85Br0.2)3 and Cs0.05FA0.83MA0.12PbI3 were explored. By using a mixture of ethanol-acetonitrile, we obtained uniform films with a one-step deposition method, presenting a mixture of α- FAPbI3 and δ- FAPbI3 phases. Those results provide a roadmap to achieve scalable precursors for highly stable and efficient perovskite solar cells.

 

The authors gratefully acknowledge the financial support provided by the committee for the development of research (CODI) of the Universidad de Antioquia, in the framework of the project 2017-16000.

© Fundació Scito
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