Engineering of modular organic photovoltaic devices with dye sensitized architecture†
Abstract
In the last two decades, organic photovoltaic devices, primarily bulk heterojunction solar cells, have progressed much in device performances but the requirement of a crystalline nanoscale phase separated domain has limited the modular characteristic of the approach and very specific donor : acceptor blends are preferred. Here, we show an alternative organic photovoltaic platform with dye sensitized architecture with excellent modular characteristics. Aniline in situ polymerized in the presence of different amounts (10, 12, 16, and 20 mg) of N,N-di((S)-1-carboxylphenylalanine)-3,4:9,10-perylenetetracarboxyldiimide (PPA) in citric acid medium results in composites designated as PP10, PP12, PP16 and PP20, respectively. Dye-sensitized organic solar cells fabricated with PP16 and N719 dye exhibit the highest power conversion efficiency (PCE) of 4.32%. SEM study reveals dense rod-like nanosphere morphology; FTIR, UV-vis, and photoluminescence spectra suggest the presence of a π-stacking interaction between PPA and polyaniline (PANI). Incident photon to current conversion efficiency (IPCE) results exhibit a maximum of 62% conversion of incident photons absorbing in the range of 360–680 nm. The lifetime of photo-injected electrons measured from impedance spectra confirms that the PP16 device has the highest lifetime (7.7 ms) accounting for the highest PCE. Comparison with the PCE of a reference device clearly indicates the influence of dopant acid of PANI and influence of interfacial interactions through a π-stacking process towards photovoltaic performance.