Soft colloidal quantum Wells IMage Sensing (SWIMS)

软图像传感器有望在我们未来的日常生活中发挥重要作用。它们可以监测我们身体的生理信息，以提供实时、非侵入性的医疗诊断，以及通过无线通信捕获和分享照片、视频。然而，目前的图像传感电子设备不容易集成到人体中，因为它们由刚性半导体光电探测器组成，并与用于颜色识别的光学滤光片集成在一起。此外，滤光片的使用对光程差产生了额外的要求，这限制了可折叠性并限制了探测器阵列的分辨率。为了克服这些技术限制，只检测特定波长内的光的无滤光片可折叠光电探测器已经成为构建软图像传感器的关键元件。胶体量子点、金属卤化物钙钛矿和有机光电探测器表现出了良好的柔韧性和探测性。然而，它们广泛的光吸收意味着需要添加滤光片，以使它们特定于某种颜色的光。到目前为止，最成功的无滤光片模式是基于电荷收集窄化(CCN)光电二极管，这是一种将特定颜色的光转换为电流的半导体设备。然而，由于窄带响应是通过控制光生电荷收集效率来提供的，因此通常需要微米厚的结，这导致阵列具有更大的像素间串扰和频率带宽限制的可能性。已经证明，使用高反射率腔可以减小结的厚度，但仍然存在一些挑战。在这项研究中，我们的目标是解决这些挑战，以帮助找到合适的半导体，这些半导体使用无毒元素，并且能够有效地探测到厚度仅为几百纳米的特定波长内的光。如果成功，我们将朝着环保型软图像传感器更近一步，具有许多应用的潜力。在溶液处理半导体的所有形式中，最近发现的二维(2D)胶体量子阱(CQW)在软图像测量应用中非常有希望，它们不仅具有高颜色纯度和超箭全宽半高宽(FWHM)，而且还表现出与柔性电子设备的良好兼容性，例如独特的拉伸增强光学偏振。与胶体量子点不同，由于对短轴的原子精确定义，CQW系综没有不均匀的展宽，这也是CQW表现出迄今报道的任何溶液处理材料中最窄的系综吸收和发射光谱的原因。然而，这一成功的隐约可见的事实是，所有报告的CQW都包括有毒的重金属(例如，镉和铅)，而无毒的CQW或CQW窄带光电探测器的制造进展甚微。因此，这项提议旨在通过使用无毒的、机械可拉伸的2D溶液处理的CQW来制造软图像传感器来实质性地解决这一挑战。这一建议首先从无毒CQW的生长和表面功能化开始，然后预测FAST CCN的新的空腔和电荷传输层。这项拟议的工作将考虑限制频率带宽的关键因素，并将演示软图像测量场景中基于CCN的多色光电二极管的喷墨打印。该项目的高影响力目标是展示一种可拉伸和机械整合的CQWs图像传感器。这项提议将以加的夫大学现有的化合物半导体研究专业知识为基础，与牛津大学、剑桥大学和布里斯托尔大学、TCL企业研究公司、华为英国公司、Glaia公司、99P回收公司和Hamamatsu英国公司密切合作。

Soft image sensors are expected to take vital roles in our future daily life. They can monitor the physiological information of our body to provide real-time, noninvasive medical diagnostics, as well as capture and share photos, videos via wireless communications. However, current image sensing electronics cannot be integrated easily into humans, because they are made of rigid semiconductor photodetectors and integrated with optical filters for colour discrimination. In addition, the use of filter creates additional requirements on the optical path difference, which confines the foldability and limits the resolution of the detector array. To overcome these technological limitations, filterless foldable photodetectors which only detect light within a specific wavelength have emerged as critical elements for building soft image sensors. Colloidal quantum dots, metal halide perovskite and organic photodetectors have shown excellent flexibility and detectivity. However, their broad light absorption means filters need to be added to make them specific to a certain colour of light. So far, the most successful filterless model is based on charge collection narrowing (CCN) photodiodes, which are semiconductor devices that convert the specific colour of light into an electrical current. However, since the narrowband response is delivered by controlling photogenerated charge collection efficiency, micrometres thickness junction is often required, which results in an array with a greater likelihood of interpixel cross-talk and frequency bandwidth limitations. It has been demonstrated that the junction thickness can be reduced by using high reflectivity cavities, but a number of challenges still remain. In this research, we aim to tackle these challenges to help find suitable semiconductors that use non-toxic elements and are able to efficiently detect light within a specific wavelength of interest at thicknesses as little as few hundred nanometres. If successful, we would be moving a step closer to an eco-friendly soft image sensor with the potential for many applications. Among all incarnations of solution-processed semiconductors, the recently discovered two-dimensionally (2D) Colloidal Quantum Wells (CQWs) are highly promising for soft image sensor applications, not only do they offer high colour purity with ultranarrow full-width at half-maximum (FWHM) but they also exhibit excellent compatibility with flexible electronics, such as unique stretching enhanced optical polarisation. Unlike colloidal quantum dots, CQW ensembles have no inhomogeneous broadening due to an atomically-precise definition of the short axis and is the reason why CQWs exhibit the narrowest ensemble absorption and emission spectrum of any solution-processed material reported to date. However, looming over much of this success is the fact that all the reported CQWs include toxic heavy metals (e.g., cadmium and lead), and little progress has been made on the fabrication of non-toxic CQWs or CQW narrowband photodetectors. This proposal is therefore designed to substantially address this challenge by using non-toxic mechanically stretchable 2D solution-processed CQWs for the fabrication of soft image sensors. This proposal starts from the growth and surface functionalisation of non-toxic CQWs followed by predictions of the new cavity and charge transport layers for fast CCN. The proposed work will consider the key factors limiting frequency bandwidth, and will demonstrate the inkjet printing of multi-coloured CCN-based photodiodes in a soft image sensor scenario. The high impact objective of this project is the demonstration of a CQWs image sensor which is stretchable and mechanically conformable. This proposal will be underpinned from the established compound semiconductor research expertise at Cardiff University, in close collaboration with Oxford, Cambridge and Bristol University, TCL Corporate Research, Huawei UK, Glaia, 99P Recycling and Hamamatsu UK.