双栅PIN结构双极性有机光敏场效应晶体管和高效有机光探测器研制

The extended interest in organic photodetectors is the result of qualities of organic semicongductors, such as low cost, large-area processed at low temperature and high absorption coefficient. Organic photodetectors are typically photodiodes, which are ideal for very fast signals but with most challenging problem of the relatively fast annihilation of the excitons which restrict their dissociation efficiency into free charge carriers. Organic photoFETs show higher gains and signal-to-noise ratios compared to organic photodiodes and, thanks to their similar structure, more straightforwardly integrated with OFETs into a circuit. The shift of the threshod voltage in photoFETs becomes one of the main bottlenecks for proper operation. We present a new configuration device, named dual-gate PIN type ambipolar organic photoFETs, with merits of high gains and signal-to-noise ratios, fast signal-output and accurate control of the threshod voltage. The project focus on the preparation of the proposed device, the study of operation mechanism, the formation of matching criterion and fabrication of high efficiency specific organic photodetectors.

有机光探测器的优势源于有机材料，不仅材料成本低廉，低温大面积制备工艺简单，而且光吸收系数高。有机光敏二极管是目前常用的有机光探测器件，它响应速度快，但光生激子淬灭迅速。与有机光敏二极管相比，有机光敏晶体管具有高增益和信噪比，更适合光探测，但由于阈值电压漂移问题影响了器件的稳定性。我们提出了双栅PIN场效应晶体管结构双极性有机光敏晶体管，不仅继承了有机光敏二极管的快速响应特性以及有机光敏晶体管的高增益和信噪比，而且增加了双栅能够精确控制阈值电压提高了器件的稳定性。通过器件制备及参数优化，探索器件工作机制，形成实现双栅PIN场效应晶体管结构双极性有机光敏晶体管材料、结构以及上下栅压匹配的基本准则，并针对具体光探测要求制备性能稳定的高效有机光探测器。

有机光探测器具有宽光谱响应、可大面积检测和超薄轻便等诸多优势，近些年来备受关注。但是，目前有机光探测器的性能还达不到传统的无机半导体光探测器的水平。有机光敏晶体管具有高增益和信噪比，更适合光探测。本项目制备了基于并五苯材料的光敏晶体管，器件的开关比达到10-3，阈值电压在-2.66V，场效应迁移率为0.32 cm2/Vs，光照强度为1mW时阈值电压移动0.27V，场效应迁移率增加了0.16 cm2/Vs。当Vg=10V时，器件响应率R和光电灵敏度Rl/d分别为0.18A/W和1.5。本项目选用小分子材料Rubrene和C60分别作为给体材料和受体材料，制备了不同结构的有机光电探测器件，并在此基础上，研究了影响有机光探测器带宽的因素。结果表明，带宽与器件结构、入射光波长和所用的有机半导体材料有直接的关系。器件的磁效应研究结果表明，对于由Rubrene和 C60构成的光探测器，Rubrene吸光后产生的三线态激子慢漂移速度是阻碍器件带宽提高的主要因素。另外，本项目选用具有应用于聚合物太阳能电池和晶体管中的高迁移率窄带隙聚合物PDPP3T为给体材料，PC71BM为受体材料，制备出了响应范围在300-1000nm波段的高探测率的全聚合物光探测器，在-0.5V偏压下，波长为850nm处器件的外量子效率达到27.7%，并且器件的暗电流密度低至0.64nA cm-2，这是目前报道的宽光谱有机光电探测器件中最优的暗电流值。