Electrode buffer layers via networks of polythiophene/polyaniline bottlebrushes and carbon nanotubes in organic solar cells

A new p-type electrode buffer layer (EBL) material was developed by the networks composed of multi-walled CNTs (MWCNTs) and poly(3-thiophene ethanol) (P3ThEt)-g-polyaniline (PANI) bottlebrush copolymers. The nanocomposites of CNT:P3ThEt-g-PANI were prepared in three different thicknesses (5, 15, and 25 nm) and employed as hole transport layer (HTL) in poly(3-hexylthiophene) (P3HT):phenyl-C71-butyric acid methyl ester (PC71BM) solar cells. A trade-off was detected between the sheet resistance and transmittance by elevating the HTL thickness for both pure CNT and CNT:P3ThEt-g-PANI nanocomposites. The CNT:P3ThEt-g-PANI thin films, in particular with an optimal thickness of 15 nm, were the turning points for equilibrating the film thickness, transmittance, surface roughness, and sheet resistance values. The smoothest thin films of CNT:P3ThEt-g-PANI with the thickness of 15 nm, the transmittance of 85-89%, and the sheet resistance of 5.6x10(4) Omega/sq reflected the best results of 12.85 mA/cm(2), 60.7%, and 0.68 V. Hence, a maximum power conversion efficiency (PCE) of 5.30% was acquired among all solar cells fabricated in current work. After peaking at 15 nm, the second group of proper results was recognized in CNT:P3ThEt-g-PANI (25 nm)/P3HT:PC71BM photovoltaics (10.37 mA/cm(2), 49.0%, and 0.62 V). The PCE of 3.15% for this system was even greater than the ideal performance (=2.94%) detected in the pure CNT (15 nm)/P3HT:PC71BM solar cells.