The development of polymer semiconductors has become an important topic due to its advantages oflow cost, easy fabrication, light weight, and capability to fabricate flexible large-area devices. Forexample, as the need for new clean energy sources is increasing, polymer solar cells (PSCs) are beingdeveloped rapidly and becoming a promising alternative to silicon solar cells. This thesis focuses onthe applications of polymer semiconductors in two active fields of polymeric optoelectronics: PSCs andpolymer photodetectors (PPDs). Heretofore, PSCs and PPDs were fabricated commonly using a blendof a conjugated polymer and a fullerene derivative as the active layer. Despite the wide use of fullerenederivatives, their limitations such as low absorption, morphological instability, and high costs, createda strong need to develop new acceptor materials. Therefore, all-polymer solar cells (all-PSCs) and allpolymerphotodetectors (all-PPDs) based on a blend of conjugated polymers acting as both electrondonor and acceptor are being actively pursued.We have made concerted efforts to prepare high-performance all-PSCs and all-PPDs, by specificallymodifying the acceptor molecular structure, and rationally choosing suitable donor and acceptorcombinations. This aspect of our work had two main facets:\ua0* Material synthesis: the design, synthesis and characterization of novel acceptor polymers.\ua0* Device engineering: the fabrication, optimization and characterization of all-PSCs and all-PPDs.Our efforts in the design of novel acceptor polymers focused on crystallinity and energy levelengineering via structural modifications like backbone and sidechain modulation. Also, acomprehensive comparison of the characteristic functional properties of acceptor polymers wasundertaken. Binary devices using donor and acceptor polymers with complementary absorption orsuitable energy level offset, and ternary devices were studied to further improve the performance of all-PSCs. High efficiencies of 8.0% and 9.0% are achieved for binary all-PSCs and ternary all-PSCs,respectively. Additionally, high-performance all-PPDs exhibiting low dark current density (Jd) and highresponsivity (R) under -5 V bias were demonstrated. Based on the results presented herein, we are nowmoving closer to understanding the correlation between the polymer structure, blend morphology, anddevice performance. This thesis also provides a guideline for developing all-PSCs and all-PPDs withimproved performance
