Solution‐processed, color‐selective organic photodetectors are uniquely positioned to deliver high‐performance, low‐cost, multicolor light sensors/imagers beyond the limitations of conventional, color‐filter‐based technologies. To realize such potential, however, a prominent challenge has been the solution‐based, monolithic integration of vertically stacked organic photodetectors, which would enable multicolor sensing with optimum light collection while benefiting from the scalability, cost, and sustainability edges of solution‐based manufacturing. To tackle this challenge, this paper demonstrates, for the first time, the monolithic integration of vertically stacked solution‐processed organic photodetectors for independent, multicolor light sensing within the same pixel area. The solvent orthogonality challenge is tackled by selecting polymer‐based photoactive layers and an insulating polymeric spacer—for independent biasing and photocurrent readout—with compatible processing conditions. Based on the suitable characteristics of blue‐ and green‐sensitive standalone devices, the vertically stacked, monolithic device architecture is optimized by also incorporating semitransparent electrodes for photons to reach deep into the stack. The resultant device architecture enables efficient blue‐ and green‐selective photodetection with state‐of‐the‐art linearity, alongside speed of response adequate for real‐world applications. Based on its solution‐processability and modularity, this approach paves the way for the facile, solution‐based fabrication of organic imagers covering multiple spectral regions with high sensitivity and resolution.
Ongoing developments in machine vision, wearables, and the Internet of Things have led to strong demand for easy-to-fabricate, color-selective photodetectors. Narrowband-absorption-type (NBA) printable organic photodetectors provide an attractive solution, given their spectral robustness and fabrication simplicity. However, a key remaining challenge to realizing their potential is to concurrently achieve high photoconversion efficiency and spectral selectivity. Herein, this challenge is tackled by investigating a non-fullerene-based route to green-selective, solution-based photodetectors. Soluble phthalocyanine acceptor PhO-Cl6BsubPc is considered due to its high absorption selectivity to green photons. Blends with soluble quinacridones are pursued to realize the ideal of a donor:acceptor layer selectively absorbing the target photons throughout its volume. Amongst quinacridones, a latent-pigment route to the solution-based deposition of trans-quinacridone (QA) enables well-intermixed QA:PhO-Cl6BsubPc layers. Green-selective photodetectors with cutting-edge performance are thus realized, achieving a 25 % increase in external quantum efficiency compared to all prior solution-based NBA implementations, as well as a nearly five-fold enhancement of the green-to-blue spectral rejection ratio. The merit of this approach is further illustrated by comparison with the corresponding fullerene-based photodetectors. By demonstrating an approach to solution-based NBA photodetectors with cutting-edge photoconversion efficiency and spectral selectivity, this study represents an important step toward printable, high-performance organic color sensors and imagers.
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