Abstract
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 C61-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.
Highlights
Buffer layer ((ABL) or hole transporting layer), which transports holes to the anode, or a cathode buffer layer, which transports electrons to the cathode[6]
For the pristine PEDOT:PSS and PEDOT:PSS@DOH(1.0 wt%) films, the root mean square roughness values were 0.757 and 0.579 nm, respectively[32]. These results indicate that the incorporation of DOH into the PEDOT:PSS rearranged the PEDOT and PSS chains, while the smoother buffer layer on top of the indium tin oxide (ITO) improved the connection between the PEDOT-rich regions in both the parallel and vertical directions[33]
We demonstrated an efficient and new approach for improving the performance and stability of the polymer solar cells (PSCs) by using an ABL included with a multifunctional organic additive (2, 3 dihydroxypyridine, DOH) in the PEDOT:PSS film
Summary
PEDOT:PSS as an anode buffer layer for enhanced photovoltaic performance and stability in received:27October2016 accepted: 17 February 2017 polymer solar cells Published: 24 March 2017. To evaluate the device performance, the most actively studied photoactive blend system (P3HT:PC61BM) was utilized to fabricate the BHJ PSCs. Subsequently, we examined the influence of DOH on the important properties of the PEDOT:PSS film, such as the electrical conductivity, WF tuning at the ITO/PEDOT:PSS@DOH interface, surface morphology, topography, hole mobility across the ITO/PEDOT:PSS@DOH interface, optical transparency, PV performances and device stability. Our results clearly revealed the multiple roles of DOH and informed that the blending of mild basic DOH concurrently tunes the energy level alignment and surface texture, enhances the electrical conductivity and hole mobility, yields adequate optical transparency and improves PV performances. The inclusion of mild basic DOH in PEDOT:PSS film improved both the photovoltaic performances and the stability of the BHJ PSC
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