Electroluminescent devices based on organic semiconductors have attracted significant attention owing to their promising applications in flat-panel displays. The conventional display pixel consisting of side-by-side arrayed red, green and blue subpixels represents the mature technology but bears an intrinsic deficiency of a low pixel density. Constructing an individual color-tunable pixel that comprises vertically stacked subpixels is considered an advanced technology. Although color-tunable organic light-emitting diodes (OLEDs) have been fabricated using the vacuum deposition of small molecules, the solution processing of conjugated polymers would enable a much simpler and inexpensive manufacturing process. Here we present the all-solution processing of color-tunable OLEDs comprising two vertically stacked polymer emitters. A thin layer of highly conducting and transparent silver nanowires is introduced as the intermediate charge injection contact, which allows the emission spectrum and intensity of the tandem devices to be seamlessly manipulated. To demonstrate a viable application of this technology, a 4-by-4 pixelated matrix color-tunable display was fabricated.

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Manufacturing commercially viable perovskite solar cells still requires appropriate low‐temperature and scalable deposition processes to be developed. While α‐phase FAPbI3 has higher thermal stability and broader absorption than MAPbI3, there still is no report of a pure α‐phase FAPbI3 perovskite film obtained by a scalable printing method. Moreover, spontaneous conversion of the α‐phase to non‐perovskite δ‐phase under ambient conditions poses a serious challenge for practical applications. Herein, a scalable and fully solution based printing method for the fabrication of pure α‐phase FAPbI3 perovskite solar cells is reported. Through adding N‐methyl pyrrolidone and methylammonium chloride to the dimethylformamide based precursor solution to control the crystallization, and vacuum or air‐flow assisted film drying, pure α‐FAPbI3 phase is obtained by doctor blading. The resulting α‐FAPbI3 film is highly stable, with no δ‐FAPbI3 phase being formed even after keeping it in an ambient atmosphere over a period of 200 days without encapsulation. In addition, a fully solution processed PSC with a PCE of 16.1% is processed by the vacuum assisted method, and 17.8% by the air‐flow assisted method. Replacing silver with a printed carbon electrode provides a stable PCE up to 15% for the vacuum assisted and 16.4% for the air‐flow assisted method, which is the highest performance of FAPbI3 solar cells to date. Compared with MAPbI3, the fully printed FAPbI3 perovskite devices exhibit a remarkable thermal stability in humid atmospheres which makes them a promising candidate for scalable production and commercialization.

and on the other hand do not cause a substantial loss of efficiency. [1] Besides high efficiency and longevity, cost competitive PSCs must meet two further essential requirements: they must not contain expensive materials and they must be processed by high-throughput sheet-to-sheet (S2S) or roll-to-roll (R2R) processes with low capex and low operating cost. [2] Reducing the bill of materials (BOM) is essential, as most efficient lab-size PSCs comprise noble metal electrodes (e.g., gold and silver) and expensive hole transport materials (e.g., spiro-OMeTAD), which dominate the material costs and are thus not acceptable for large-scale applications. [3] Furthermore, thermally evaporated gold and silver electrodes cause significant energy consumption and thus limit the energy payback time of the photovoltaic technology. Even worse, they deteriorate cell performance, due to migration of halogen atoms from the perovskite layer to form gold and silver halides. [4] Therefore, carbon has been employed as the counter electrode, reducing material cost, improving device stability, simplifying the device fabrication process, and thus, enabling large-scale processing of PSCs. [5] In addition to reducing the BOM, sheet-to-sheet and especially roll-to-roll printing processes are proven to reduce production costs compared to vacuum-based processes. Thus, up-scalable manufacturing technologies for PSCs must be fully compatible to Scalable deposition processes at low temperature are urgently needed for the commercialization of perovskite solar cells (PSCs) as they can decrease the energy payback time of PSCs technology. In this work, a processing protocol is presented for highly efficient and stable planar n-i-p structure PSCs with carbon as the top electrode (carbon-PSCs) fully printed at fairly low temperature by using cheap materials under ambient conditions, thus meeting the requirements for scalable production on an industrial level. High-quality perovskite layers are achieved by using a combinatorial engineering concept, including solvent engineering, additive engineering, and processing engineering. The optimized carbon-PSCs with all layers including electron transport layer, perovskite, hole transport layer, and carbon electrode which are printed under ambient conditions show efficiencies exceeding 18% with enhanced stability, retaining 100% of their initial efficiency after 5000 h in a humid atmosphere. Finally, large-area perovskite modules are successfully obtained and outstanding performance is shown with an efficiency of 15.3% by optimizing the femtosecond laser parameters for the P2 line patterning. These results represent important progress toward fully printed planar carbon electrode perovskite devices as a promising approach for the scaling up and worldwide application of PSCs.