<p>Supplementary material</p><p>Insights into optoelectronic properties of anti-solvent treated perovskite films Asmat Nawaza,b,c, Ali Koray Erdincb, Burak Gultekinb, Muhammad Tayyiba, Ceylan Zafer*b, Kaiying Wanga, M.Nadeem Akrama</p><p>Ka Kan Wong,c Sajjad Hussain,c Lukas Schmidt-Mendec, Azhar Fakharuddin*c a Dept of Micro and Nano Systems Technology, University College South East Norway, Borre 3184 Norway b Ege University, Solar Energy Institute, 35100 Bornova, Izmir, Turkey c Department of Physics, University of Konstanz, D-78457, Konstanz, Germany</p><p>Corresponding authors: [email protected] (Ceylan Zafer), [email protected] (Azhar Fakharuddin)</p><p>1 Supplementary material</p><p>Figure SI-1: Steady-state photoluminiscence spectra of as-prepared and toluene washed perovskite films on glass. The films were excited using a pulsed laser exc 405 nm.</p><p>(a) (b) </p><p>Figure SI-2 (a): PbI2 coated films (w/toluene assisted) on glass (left), w/o toluene (right) (b) UV-VIS absorption spectra of PbI2 films with and without toluene treatment.</p><p>The toluene drenching effects was investigated on the inorganic PbI2 films. 40wt% PbI2 solution was prepared in gamma butyrolactone (GBL) and stirred for 1hour. PbI2 solution was spin coated on two substrates at 2000 rpm and during spinning; one sample was treated with 100 toluene. Both films were annealed at 110˚C for 20min. The toluene treated film was transparent, while the other film was rough and opaque as shown in Figure SI-21-a. Figure SI-2b shows the absorbance spectra of PbI2 films with and without toluene treatment. Both films are yellow. This</p><p>2 Supplementary material can be seen in UV-VIS spectra as well, especially the film, which is prepared with toluene. The curve between 550nm and 570nm wavelengths belong to the yellow color. The toluene treated film is very smooth and highly transparent; therefore, it has higher transmittance and lower absorbance than the one without toluene treatment, which scatters the light strongly leading to an increase in the observed absorbance. For the full MAPbI3 films, this case is exactly the opposite.</p><p>Annealing the MAPbI3 films leads to the typical color change to dark brown as body-centered tetragonal phase crystal structure transforms to cubic phase. </p><p>3 Supplementary material</p><p>(a)Without solvent washing (b) Washing with solvent (toluene)</p><p>4 Supplementary material</p><p>Fig SI-3: Optical micrograph of the perovskite film in GBL (a) washing without solvent (b) washing with solvent (toluene). </p><p>5</p>