Scalable Manufacturing of Perovskite Polymer Composites Towards Advanced Optoelectronics

• Other Authors: Shan, Xin (author)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Engineering
• Online Access: http://purl.flvc.org/fsu/fd/2018_Fall_Shan_fsu_0071E_14859

Halide perovskites bring an unprecedented opportunity for low-cost high performance optoelectronic devices due to their extraordinary optical and electrical properties along with their solution processible nature. The record power conversion efficiency (PCE) of perovskite solar cells (23.3%) has surpassed polycrystalline silicon, copper indium gallium selenide (CIGS), and cadmium telluride (CdTe). In addition, the record external quantum efficiency (EQE) of perovskite light-emitting diodes (20.3%) is on par with the organic light-emitting diodes (OLEDs) and quantum dot light-emitting diodes (QLEDs). Benefiting from the superb properties of perovskites, there is increasing interests in fabricating perovskite optoelectronics in a large scale as well as with low elastic modulus (high flexibility and stretchability). Although the efficiencies of perovskite optoelectronics increase dramatically in the past few years, there are still concerns that cause short lifespan in perovskite optoelectronics, such as ion migration induced intrinsic perovskite instability, oxygen, moisture, non-radiative recombination at the constituent layer interfaces. This dissertation explores the possibility of scalable manufacturing of optoelectronics with low elastic modulus using perovskite polymer composites. Besides, this dissertation also studies the ion migration induced in-situ junction formation in halide perovskite polymer composite films and perovskite single crystals. Device failure mechanism caused by ion migration is also investigated in this dissertation. Perovskite thin film processing is essential for perovskite optoelectronics scalable manufacturing. In this dissertation, firstly, a uniform and pin-hole free thin film was processed using perovskite polymer composites. Perovskite LEDs were fabricated using the composite emitters. It has been discovered that an in situ homogeneous p-i-n junction can be developed in the composite emitter when an external bias is applied. The junction formation enables very efficient charge carrier transportation in perovskite LEDs without using additional electron transport layers (ETLs) and hole transport layers (HTLs). While a typical LED usually adopts a multi-layer structure, including both ETLs and HTLs. The unique simplified perovskite LED structure without using ETLs and HTLs is called "single-layer" structure. Moreover, scalable manufacturing of fully printed perovskite LEDs and intrinsically stretchable LEDs with robust mechanical performance is demonstrated benefiting from the "single-layer" structure in this dissertation. A stable junction formation is the basis of a stable perovskite LED. In this dissertation, the in-situ p-i-n homojunction in the perovskite polymer composites and perovskite single crystals are studied. AC impedance spectroscopy is used to study the junction formation and propagation of the perovskite polymer composites under an external electric field. Discharge current-voltage (I-V) characteristics and temperature dependence study are also conducted to support the ion migration induced junction formation and relaxation. It is a potential pathway to obtain highly stable perovskite LEDs by immobilizing the ions and stabilizing the junction. === A Dissertation submitted to the Department of Industrial and Manufacturing Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. === Fall Semester 2018. === October 31, 2018. === composite, junction formation, LEDs, perovskite, polymer === Includes bibliographical references. === Zhibin Yu, Professor Directing Dissertation; Jianping Zheng, University Representative; Zhiyong Liang, Committee Member; Omer Arda Vanli, Committee Member.