Improved performance of ternary blend polymer solar cells via work function tuning and suppressed interface recombination using hybrid PEDOT:PSS-graphene oxide hole transport layer

Abstract

In this work, we present a solution-processed poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate)-graphene oxide (PEDOT:PSS-GO) composite as a novel hole transporting material with excellent hole extraction properties which boost the performance of ternary blend polymer solar cells (TPSCs). TPSCs employing ternary blend active layer composed of two conjugated polymer donors i.e., poly(3-hexyl)thiophene):poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2–6-diyl)] (P3HT:PTB7-th) blended with organic acceptor [6,6]-phenyl C71-butyric-acid-methyl-ester (PC71BM) have shown high performance when PEDOT:PSS-GO is used as hole transport layer (HTL). The best TPSC, ITO/PEDOT:PSS-GO(1:1)/P3HT:PTB7-th:PC71BM(0.3:0.7:1)/LiF/Al, has showed improved performance with power conversion efficiency (PCE) as high as 7.1% and external quantum efficiency of 70–80% in a broad wavelength range of 350–800 nm. There is an increment of 55% in PCE compared to TPSCs with PEDOT:PSS-only HTL. The improvement in performance of TPSCs with PEDOT:PSS-GO HTLs is predominantly attributed to the better charge extraction and carrier collection owing to significantly reduced photo-generated exciton lifetime, tuned work function, reduced potential barrier at HTL/active layer interface, remarkably improved film morphology, and increased conductivity of PEDOT:PSS-GO films. PEDOT:PSS-GO HTLs significantly boost the performance and lifetime stability of (P3HT:PTB7-th:PC71BM) ternary blend-based TPSCs. Our work demonstrate the superior hole transport properties of PEDOT:PSS-GO over conventional PEDOT:PSS HTLs for the accelerating development of TPSCs.