ABSTRACT

Shortwave infrared (SWIR) optical sensing and imaging are essential to an increasing number of next-generation applications in communications, process control or medical imaging. An all-organic SWIR upconversion device (OUC) consists of an organic SWIR sensitive photodetector (PD) and an organic light-emitting diode (OLED), connected in series. OUCs directly convert SWIR to visible photons, which potentially provides a low-cost alternative to the current inorganic compound-based SWIR imaging technology. For OUC applications, only few organic materials have been reported with peak absorption past 1000 nm and simultaneous small absorption in the visible. Here, we synthesized a series of thermally stable high-extinction coefficient donor-substituted benz[cd]indole-capped SWIR squaraine dyes. First, we coupled the phenyl-, carbazole-, and thienyl-substituted benz[cd]indoles with squaric acid (to obtain the SQ dye family). We then combined these donors with the dicyanomethylene-substituted squaraine acceptor unit, to obtain the dicyanomethylene-functionalized squaraine DCSQ family. In the solid state, the absorbance of all dyes extended considerably beyond 1100 nm. For the carbazole- and thienyl-substituted DCSQ dyes, even the peak absorptions in solution were in the SWIR, at 1008 nm and 1014 nm. We fabricated DCSQ PDs with an external photon-to-current efficiency over 30%. We then combined the PD with a fluorescent OLED and fabricated long-term stable OUCs with peak sensitivity at 1020 nm, extending to beyond 1200 nm. Our OUCs are characterized by a very low dark luminance (<10⁻² cd m⁻² at below 6 V) in the absence of SWIR light, and a low turn-on voltage of 2 V when SWIR light is present.

摘要

短波红外（SWIR）光学传感和成像对于通信，过程控制或医学成像中越来越多的下一代应用至关重要。全有机SWIR上转换设备（OUC）由串联的有机SWIR敏感光电探测器（PD）和有机发光二极管（OLED）组成。OUC直接将SWIR转换为可见光子，这可能为当前基于无机化合物的SWIR成像技术提供低成本替代方案。对于OUC应用，只有极少数有机材料被报道，其峰值吸收超过1000 nm，同时可见光中的吸收也很小。在这里，我们合成了一系列热稳定的高消光系数供体取代的苯并[ cd吲哚加帽的SWIR方酸菁染料。首先，我们将苯基，咔唑和噻吩基取代的苯偶合[ cd]吲哚与方酸（获得SQ染料家族）。然后，我们将这些供体与双氰基亚甲基取代的方酸受体单元结合，以获得双氰基亚甲基官能化的方酸DCSQ家族。在固态状态下，所有染料的吸光度都大大超过了1100 nm。对于咔唑和噻吩基取代的DCSQ染料，即使溶液中的峰值吸收也位于SWIR中，分别为1008 nm和1014 nm。我们制造的DCSQ PD的外部光子电流效率超过30％。然后，我们将PD与荧光OLED结合在一起，制造出长期稳定的OUC，其峰值灵敏度在1020 nm处，延伸到1200 nm以上。我们的OUC具有非常低的暗亮度（<10 ^-2 cd m ^-2 在没有SWIR灯的情况下（低于6 V）;在存在SWIR灯的情况下为2 V的低开启电压。