In situ synthesis of gold/silver nanoparticles and polyaniline as buffer layer in polymer solar cells

A new class of hole transport layer (HTL), which is composed of gold (Au) and silver (Ag) nanoparticles (NPs), in situ synthesized with polyaniline (PANI), has been used in polymer solar cells (PSCs). Optimum metal NPs addition showed sheet resistance and transparency of 6 x 10(5)-4.9 x 10(5) (Omega/sq) and 76-81%, for Au and Ag nanoparticles respectively. The effect of simultaneous addition of Au and Ag NPs (Au(10)Ag(10)PANI) were also verified and showed sheet resistance and transparency of 4.6 x 105(Omega/sq) and 77%, respectively. Impedance spectroscopy (IS) revealed charge transport improvement in Au(10)Ag(10)PANI-based PSCs and power conversion efficiency (PCE) was enhanced 74% in comparison with PEDOT:PSS-based devices. Incident Photon-to-electron Conversion Efficiency (IPCE) analysis was performed and calculated J(sc) from IPCE was almost the same as J(sc) calculated from current-voltage analysis. The improvement is mainly related to enhancing exciton generation, improved extraction, higher conductivity and broader light absorption compared with device containing single nanoparticles, which leads to an increase in short-circuit current. High conductivity, transparency and facile method of synthesis can make the proposed materials as a qualified alternative for PEDOT:PSS in the future.