Efficiency enhancement of organic solar cells using hydrophobic antireflective inverted moth-eye nanopatterned PDMS films

Poly-dimethylsiloxane (PDMS) films with 2D periodic inverted moth-eye nanopatterns on one surface are implemented as antireflection (AR) layers on a glass substrate for efficient light capture in encapsulated organic solar cells (OSCs). The inverted moth-eye nanopatterned PDMS (IMN PDMS) films are fabricated by a soft imprint lithographic method using conical subwavelength grating patterns formed by laser interference lithography/dry etching. Their optical characteristics, together with theoretical analysis using rigorous coupled-wave analysis simulation, and wetting behaviors are investigated. For a period of 380 nm, IMN PDMS films laminated on glass substrates exhibit a hydrophobic surface with a water contact angle (θ_CA) of ≈120° and solar weighted transmittance (SWT) of ≈94.2%, both significantly higher than those (θ_CA≈ 36° and SWT ≈ 90.3%) of bare glass substrates. By employing IMN PDMS films with a period of 380 nm on glass substrates for OSCs, an enhanced power conversion efficiency (PCE) of 6.19% is obtained mainly due to the increased short-circuit current density (J_sc) of 19.74 mA cm^-2 compared to the OSCs with the bare glass substrates (PCE = 5.16% and J_sc = 17.25 mA cm^-2). For the OSCs, the device stability is also studied. Inverted moth-eye nanopatterned poly-dimethylsiloxane (IMN PDMS) films fabricated by soft imprint lithography serve as antireflection (AR) layers on glass substrates for encapsulated organic solar cells. The AR IMN PDMS film, which has a hydrophobic surface, increases the short-circuit current density and thus improves the power conversion efficiency.