This study reports the development of copper(I) thiocyanate (CuSCN) hole-transport layers (HTLs) processed from aqueous ammonia as a novel alternative to conventional n-alkyl sulfide solvents. Wide bandgap (3.4–3.9 eV) and ultrathin (3–5 nm) layers of CuSCN are formed when the aqueous CuSCN–ammine complex solution is spin-cast in air and annealed at 100 °C. X-ray photoelectron spectroscopy confirms the high compositional purity of the formed CuSCN layers, while the high-resolution valence band spectra agree with first-principles calculations. Study of the hole-transport properties using field-effect transistor measurements reveals that the aqueous-processed CuSCN layers exhibit a fivefold higher hole mobility than films processed from diethyl sulfide solutions with the maximum values approaching 0.1 cm2 V−1 s−1. A further interesting characteristic is the low surface roughness of the resulting CuSCN layers, which in the case of solar cells helps to planarize the indium tin oxide anode. Organic bulk heterojunction and planar organometal halide perovskite solar cells based on aqueous-processed CuSCN HTLs yield power conversion efficiency of 10.7% and 17.5%, respectively. Importantly, aqueous-processed CuSCN-based cells consistently outperform devices based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate HTLs. This is the first report on CuSCN films and devices processed via an aqueous-based synthetic route that is compatible with high-throughput manufacturing and paves the way for further developments

The ability to tune the electronic properties of soluble wide bandgap semiconductors is crucial for their successful implementation as carrier-selective interlayers in large area opto/electronics. Herein the simple, economical, and effective p-doping of one of the most promising transparent semiconductors, copper(I) thiocyanate (CuSCN), using C 60 F 48 is reported. Theoretical calculations combined with experimental measurements are used to elucidate the electronic band structure and density of states of the constituent materials and their blends. Obtained results reveal that although the bandgap (3.85 eV) and valence band maximum (−5.4 eV) of CuSCN remain unaffected, its Fermi energy shifts toward the valence band edge upon C 60 F 48 addition-an observation consistent with p-type doping. Transistor measurements confirm the p-doping effect while revealing a tenfold increase in the channel's hole mobility (up to 0.18 cm 2 V −1 s −1 ), accompanied by a dramatic improvement in the transistor's bias-stress stability. Application of CuSCN:C 60 F 48 as the hole-transport layer (HTL) in organic photovoltaics yields devices with higher power conversion efficiency, improved fill factor, higher shunt resistance, and lower series resistance and dark current, as compared to control devices based on pristine CuSCN or commercially available HTLs.

Recent advances in large-area optoelectronics research have demonstrated the tremendous potential of copper(I) thiocyanate (CuSCN) as a universal hole-transport interlayer material for numerous applications, including, transparent thin-film transistors, high-efficiency organic and hybrid organicinorganic photovoltaic cells, and organic light-emitting diodes (OLEDs). CuSCN combines intrinsic hole-transport (p-type) characteristics with a large bandgap (>3.5 eV) which facilitates optical transparency across the visible to near infrared part of the electromagnetic spectrum. Furthermore, CuSCN is readily available from commercial sources while it is inexpensive and can be processed at low-temperatures using solution-based techniques. This unique combination of desirable characteristics makes CuSCN a promising material for application in emerging large-area optoelectronics. In this review article, we outline some important properties of CuSCN and examine its use in the fabrication of potentially low-cost optoelectronic devices. The merits of using CuSCN in numerous emerging applications as an alternative to conventional hole-transport materials are also discussed.

Herein we present the synthesis and characterization of four conjugated polymers containing a novel chromophore for organic electronics based on an indigoid structure. These polymers exhibit extremely small band gaps of ~1.2 eV, impressive crystallinity, and extremely high n-type mobility exceeding 3 cm 2 Vs-1. The n-type charge carrier mobility can be correlated with the remarkably high crystallinity along the polymer backbone having a correlation length in excess of 20 nm. Theoretical analysis reveals that the novel polymers have highly rigid non-planar geometries demonstrating that backbone planarity is not a prerequisite for either narrow band-gap materials or ultra-high mobilities. Furthermore the variation in backbone crystallinity is dependent on the choice of co-monomer. OPV device efficiencies up to 4.1% and charge photo-generation up to 1000 nm are demonstrated, highlighting the potential of this novel chromophore class in high-performance organic electronics.

A novel, highly soluble chromophore for use in organic electronics based on an indigoid structure is reported. Copolymerization with thiophene affords an extremely narrow band gap polymer with a maximum absorption at ∼800 nm. The novel polymer exhibits high crystallinity and high ambipolar transport in OFET devices of 0.23 cm 2 V −1 s −1 for holes and 0.48 cm 2 V −1 s −1 for electrons. OPV device efficiencies up to 2.35% with light absorbance up to 950 nm demonstrate the potential for this novel chromophore in near-IR photovoltaics. ■ INTRODUCTIONThe development of novel organic conjugated polymers has gained momentum in recent times due to their possible applications in organic photovoltaic (OPV) and organic fieldeffect transistor (OFET) devices where their lower cost, light weight, and mechanical flexibility are all attractive properties. Current high performance polymers have enabled OFET devices with mobilities in excess of 2 cm 2 V −1 s −1 and OPV devices with power conversion efficiencies (PCEs) of over 8%. 1−3 Ultra-narrow band gap conjugated polymers are of great interest due to the ease of charge injection when incorporated into ambipolar OFETs and also their near-IR optical absorption for use in both tandem and transparent OPV devices. 4 Considerable interest has focused on planar bis-lactam containing polymers such as diketopyrrolopyrrole (DPP, 1) 5 and isoindigo (2). 6 The electron withdrawing nature of the lactam core alongside its planarity has enabled DPP and isoindigo containing conjugated polymers to reach both OPV PCEs and OFET mobilities.Indigo (3) is the most produced natural dye worldwide and has a highly planar structure arising from intramolecular hydrogen bonding between the oxygen and the amide protons of the indol-3-one units. 7 Upon photoexcitation, rotation about the central carbon−carbon bond can effect trans−cis isomerization 8 as well as either single or double proton transfer, resulting in rapid energy loss through internal conversion, thereby negating any potential for OPV devices. 9 As a semiconductor in OFET devices, indigo has shown hole mobilities up to 1 × 10 −2 cm 2 V −1 s −1 . 10 More recently, functionalized indigoids have been investigated, and the mobility can be slightly enhanced to 1.3 × 10 −2 cm 2 V −1 s −1 using 5,5′-dichloroindigo. 11 Crucially, the use of naturally occurring compounds as building blocks for materials in organic electronics can begin to address the issues of sustainability associated with them. As an example, Cibalackrot (7,14-diphenyldiindolo[3,2,1-de:3′,2′,1′-ij][1,5]naphthyridine-6,13-dione, INDP) is an indigo derivative first synthesized in Figure 1. Bis-lactam containing compounds and polymer building blocks. Article pubs.acs.org/Macromolecules