Solution-processed Hybrid Materials for Light Detection

Inorganic semiconductors form the foundation of modern electronics and optoelectronics. These materials benefit from excellent optoelectronic properties, but applications are generally limited due to high cost of fabrication. More recently, organic semiconductors have emerged as a low-cost alternative for light emitting devices. Organic materials benefit from facile, low temperature fabrication and offer attractive features such as flexibility and transparency. However, these materials are inherently limited by poor electronic transport. In recent years, new materials have been developed to overcome the di- chotomy between performance and the cost. Hybrid organic–inorganic semiconductors combine the superior electronic properties of inorganic materials with the facile assembly of organic systems to yield high-performance, low- cost electronics. This dissertation focuses on the development of solution-processed light detectors using hybrid material systems, particularly colloidal quantum dots (CQDs) and hybrid perovskites. First, advanced architectures for colloidal quantum dot light detectors are presented. These devices overcome the responsivity–speed–dark current trade-off that has limited past reports of CQD-based devices. The photo-junction field effect transistors presented in this work decrease the dark current of CQD detectors by two orders of magnitude, ultimately reducing power consumption (100×) and noise current (10×). The detector simultaneously benefits from high gain (∼10 electrons/photon) and fast time response (∼10 μs). This represents the first CQD-based three-terminal-junction device reported in the literature. Building on this success, hybrid perovskite devices are then presented. This material system has become a focal point of the semiconductor research community due to its relatively unexplored nature and attractive optoelectronic properties. Herein we present the first extensive electronic characterization of single crystal organolead hybrid perovskites for the first time. High mobility and long diffusion length (μ > 100 cm2 /V s, D > 10 μm), supported by an exceptionally low density of trap states in the bandgap (ntrap ∼ 10^10 cm−3 ), were found. This material was then implemented to produce a high-performance visible-light detector with high gain (> 10^4 electrons/photon superior to previously reported perovskite detectors) and high gain–bandwidth product (> 10^8 Hz).Ph.D