Efficient methylammonium lead triiodide CH3NH3PbI3 perovskite solar cells with improved surface properties using PM6 (PBDB-T-2F) polymer

Polymer additives are extensively used and serve a crucial role in the advancement of CH3NH3PbI3 perovskite photovoltages. This work demonstrates the effect of Poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c']dithiophene-4,8-dione)PBDB-T-2F (PM6) at various concentrations on the crystallinity, surface structure, optical and electrical properties of CH3NH3PbI3 perovskite thin films. Polymer molecules are utilized to promote the growth of crystal particles in the active layer. The chemical reaction between their functional groups and the perovskite absorber and transportation layers leads to defect passivation and improved device efficiency. The results show that the absorption spectra of CH3NH3PbI3:PM6 perovskite thin films cover the extensive absorption spectra in the UV and visible light range between 500 and 800 nm, indicating that CH3NH3PbI3:PM6 perovskite is an effective visible light absorber. The PL intensity decreased as the polymer PM6 concentration increased up to 6 mg/ml, then increased when the concentration of PM6 was raised to 8 mg/ml. Quenching the sample with 6 mg/mL of PM6 caused rapid electron transfer to the substrate. According to surface morphology findings, the perovskite film's irregularity was reduced from 37.05 nm for pure thin film to 12.27 nm when added 6 mg/ml of PM6. The 6 mg/mL PM6 film exhibited the most uniformity and fluidity. The surface of the perovskite film was transformed into smooth, compacted pores with a particle size of 2 µm, which could facilitate charge transport for enhanced photovoltaic performance. The solar cell devices had a PCE of 14.68 %, a short-circuit current density of 19.32 mA/cm2, an open circuit voltage of 1.20 V, and a fill factor of 63.35 %.