Functional solid additive modified PEDOT: PSS as an anode buffer layer for enhanced photovoltaic performance and stability in polymer solar cells

Poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) is most commonly used as an anode buffer layer in bulk-heterojunction (BHJ) polymer solar cells (PSCs). However, its hygroscopic and acidic nature contributes to the insufficient electrical conductivity, air stability and restricted photovoltaic (PV) performance for the fabricated PSCs. In this study, a new multifunctional additive, 2,3-dihydroxypyridine (DOH), has been used in the PEDOT: PSS buffer layer to obtain modified properties for PEDOT: PSS@DOH and achieve high PV performances. The electrical conductivity of PEDOT: PSS@DOH films was markedly improved compared with that of PEDOT: PSS. The PEDOT: PSS@ DOH film exhibited excellent optical characteristics, appropriate work function alignment, and good surface properties in BHJ-PSCs. When a poly(3-hexylthiohpene):[6,6]-phenyl C-61-butyric acid methyl ester blend system was applied as the photoactive layer, the power conversion efficiency of the resulting PSCs with PEDOT: PSS@DOH(1.0%) reached 3.49%, outperforming pristine PEDOT: PSS, exhibiting a power conversion enhancement of 20%. The device fabricated using PEDOT: PSS@DOH (1.0 wt%) also exhibited improved thermal and air stability. Our results also confirm that DOH, a basic pyridine derivative, facilitates adequate hydrogen bonding interactions with the sulfonic acid groups of PSS, induces the conformational transformation of PEDOT chains and contributes to the phase separation between PEDOT and PSS chains.