Improvement of both efficiency and stability in organic photovoltaics by using water-soluble anionic conjugated polyelectrolyte interlayer

Although the prominent progress of the conjugated polyelectrolytes (CPEs) in organic photovoltaics (OPVs), the reliability of the device with CPEs was not mainly focused up to date and furthermore the principle of interfacial dipole moment μID and corresponding energy level alignment in the device with a CPE interlayer were not clearly understood to explain the improved power conversion efficiency PCE. We report a water-soluble CPE, poly(2,5-bis(3-sulfonatopropoxy)-1,4-phenylene, disodium salt-alt-1,4-phenylene) (PPP-OPSO3) interlayer that increases both the device lifetime under continuous irradiation and PCE of OPVs. The μID of a PPP-OPSO3 interlayer that is in intimate contact with adjacent layers can be increased by nano-morphological control; as a result, the built-in potential and device characteristics are significantly enhanced. We investigated the mechanism by which the PPP-OPSO3 morphology affected of energetic alignment and enhanced characteristics. The PPP-OPSO3 interlayer greatly increased the PCE to 6.7%, which is significantly greater than in the device with Al (5.0%) and increased half-life time LT50 under continuous simulated solar irradiation by 2.7 times despite the solution processing of water-dissolved PPP-OPSO3.