Control of the Morphology and Crystallinity of a PbI2 Layer for Large-Area Perovskite Films Prepared by Close Space Sublimation

• Published in: ACS applied energy materials 2018-08, Vol.1 (8), p.3843-3849
• Main Authors: Pérez-Gutiérrez, Enrique, Percino, M. Judith, Montoya, Diana Marcela, Solis-Ibarra, Diego, Cerón, Margarita, Barbosa-García, Oracio
• Format: Article
• Language: English
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.8b00610

In this work, homogeneous PbI2 films were prepared by the spin-coating technique from PbI2-DMF solutions heated at temperatures ranging from room temperature to 120 °C. The homogeneity and morphology of the films change according to the used temperature of solution and are related to the size and distribution of PbI2 grains; the best crystallinity was observed when PbI2 solution was preheated at 100 °C. Lead halide perovskite films were prepared by close space sublimation of CH3NH3I over the prepared PbI2 films, and the area of the deposited films was 5 cm2. The transformation of PbI2 into perovskite was carried out at 100 °C under a pressure of −0.8 bar. A remarkable issue reported here is that, by controlling the morphology of the PbI2 layer with the temperature of PbI2-DMF solutions, the final features of MAPbI3 films can be controlled without requiring extra treatment. Therefore, the device with the best performance, out of a set fabricated with architecture ITO/PEDOT:PSS/perovskite/PC71BM/cathode, corresponded to the PbI2 film deposited at 100 °C. This device reached an efficiency of 8.7%. As a cathode, an eutectic alloy of Bi:In:Sn with a melting point of 65 °C was easily deposited without the use of high vacuum. Thus, this work describes a practical way to fabricate perovskite solar cells with efficiencies up to 8.7%.