An inkjet printed, biocompatible, heterostructure photodetector is described that was constructed using inks of photo-active molybdenum disulfide (MoS 2 ) and electrically conducting graphene which facilitated charge collection of the photocarriers. The importance of such devices stems from their potential utility in age-related-macular degeneration, which is a condition where the photosensitive retinal tissue degrades with aging, eventually compromising vision. The absence of effective therapeutic remedies for patients with this disorder has motivated the development of such devices to restore some degree of visual function. Inkjet printed, flexible prosthetic devices offer design simplicity where additive manufacturing can enable large format, low-cost arrays. The biocompatible inkjet printed two-dimensional heterojunction devices were photoresponsive to broadband incoming radiation in the visible regime, and the photocurrent I ph scaled proportionally with the incident light intensity, exhibiting a photoresponsivity R~0.30 A/W. This is 10 3 times higher compared to prior reports, and detectivity D was calculated to be~3.6 × 10 10 Jones. Straindependent measurements were also conducted with bending, indicating the feasibility of such devices printed on flexible substrates. Drop cast and printed CT-MoS 2 inks were characterized using techniques, such as Raman spectroscopy, photoluminescence measurements and scanning electron microscopy. Both mouse embryonic fibroblast and human esophageal fibroblast were used for the biocompatibility analysis for inks drop cast on two types of flexible substrates, polyethylene terephthalate and polyimide. The biocompatibility of inks formed using two-dimensional graphene and MoS 2 on polyimide substrates was extremely high, in excess of 98% for mouse embryonic fibroblast.

The synthesis of solution-processed two-dimens i o n a l( 2 D ) l a y e r e d o r g a n o h a l i d e (CH 3 (CH 2 ) 3 NH 3 ) 2 (CH 3 NH 3 ) n−1 Pb n I 3n+1 (n = 2, 3, and 4) perovskites is presented, where inkjet printing was used to fabricate heterostructure flexible photodetector (PD) devices on polyimide (PI) substrates. Inks for the n = 4 formulation were developed to inkjet-print PD devices that were photoresponsive to broadband incoming radiation in the visible regime, where the peak photoresponsivity R was calculated to be ∼0.17 A/W, which is higher compared to prior reports, while the detectivity D was measured to be ∼3.7 × 10 12 Jones at a low light intensity F ≈ 0.6 mW/cm 2 . The ON/OFF ratio was also high (∼2.3 × 10 3 ), while the response time τ on the rising and falling edges was measured to be τ rise ≈ 24 ms and τ fall ≈ 65 ms, respectively. Our strain-dependent measurements, conducted here for the first time for inkjetprinted perovskite PDs, revealed that the I p decreased by only ∼27% with bending (radius of curvature of ∼0.262 cm −1 ). This work demonstrates the tremendous potential of the inkjet-printed, composition-tunable, organohalide 2D perovskite heterostructures for high-performance PDs, where the techniques are readily translatable toward flexible solar cell platforms as well.

Terpineol leads to effective exfoliation and excitonic enhancement in solution dispersions of MoS2 and WS2, which also yields enhancement in electronic transport properties. Such dispersions are amenable to high-performance electronic and opto-electronic devices using manufacturable routes.

Continuous miniaturization of devices, for example in consumer electronics, defense and aerospace applications, is largely driven by our desire for smaller, light-weight, ultra-thin devices, where such structures on fully flexible platforms can drive down costs even further [1,2]. For flexible electronics applications in particular, the substrates pose less restrictions compared to the Si-based semiconductor industry, where in the former, a wide variety of additive manufacturing techniques easily lend themselves for the production of functional structures on arbitrary substrates within the context of what is generally referred to as 'printed electronics.' Examples of functional printed structures include printed batteries, solar cells, light emitting diodes that have been formed using organic and inorganic materials [3,4]. One commonly used additive manufacturing technique for printed electronics is ink-jet printing, which allows for a fast and cheap approach for patterning electronic devices, circuits and systems using a range of inks [5], from metallic to semiconducting, to construct active or passive structures [6].With the advent of two-dimensional (2D) layered materials (LMs), which includes quintessential 2D graphene, solution dispersions of 2DLMs have been formulated recently for ink-jet printing [7][8][9][10]. Although great progress has been made to produce liquid dispersions of 2DLMs, challenges still lie in the reliable mass production of these materials for practical applications. Some of the techniques used for solution-based exfoliation include intercalant assisted exfoliation [11,12], thermal shock [13], or shear oxidation of graphite [14] although the oxidation process results in structural defects and dispersions that are often