CH3NH3PbI3 planar perovskite solar cells with antireflection and self-cleaning function layers

Abstract

We report CH₃NH₃PbI₃ planar perovskite solar cells with multifunctional inverted micro-pyramidal structured (IMPS) polydimethylsiloxane (PDMS) antireflection (AR) layers for enhancing the device efficiency. These IMPS-PDMS films were fabricated via a facile and cost-effective soft lithography using micro-pyramidal structured silicon (Si) master molds formed by alkaline anisotropic wet-etching treatment of (100)-oriented monocrystalline Si substrates. The IMPS-PDMS laminated on the bare glass (i.e., IMPS-PDMS/glass) exhibited a higher solar weighted transmittance (T_SW) value of ∼95.2% (or the lowest solar weighted reflectance (R_SW) of ∼4.7%) than those of the bare glass and flat-PDMS/glass, i.e., T_SW/R_SW ∼ 90.7/9.1 and 91.5/8.2%, respectively. Additionally, it showed a much higher average haze ratio (H_A) value of ∼93.1% compared to the bare glass and flat-PDMS/glass (i.e., H_A ∼ 1.6 and 2.8%, respectively). By employing the IMPS-PDMS onto the outer surface of CH₃NH₃PbI₃ planar perovskite solar cells as an AR layer, an improved short-circuit current density (J_sc) value of 21.25 mA cm⁻² was obtained, as compared to the reference device and the device with flat-PDMS (i.e., J_sc = 20.57 and 20.87 mA cm⁻², respectively), while showing the almost same V_oc and FF values as those of the reference device. As a result, the power conversion efficiency was improved from 17.17 and 17.42% for the reference and flat-PDMS devices, respectively, to 17.74% for the IMPS-PDMS device. Also, the fluorooctyltrichlorosilane-treated IMPS-PDMS surface revealed a superhydrophobic behavior with a water contact angle of ∼150° which is useful for self-cleaning applications in outdoor environments.