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We present detailed studies on exciton-photon coupling and polariton emission based on a poly(1,4-phenylenevinylene) copolymer, Super Yellow (SY), in a series of optical microcavities and optoelectronic devices, including light-emitting diode (LED) and light-emitting transistor (LET). We show that sufficiently thick SY microcavities can generate ultrastrong coupling with Rabi splitting energies exceeding 1 eV and exhibit spectrally narrow, nearly angle-independent photoluminescence following lower polariton (LP) mode dispersion. When the microcavity is designed with matched LP low-energy state and exciton emission peak for radiative pumping, the conversion efficiency from exciton to polariton emission can reach up to 80%. By introducing appropriate injection layers in a SY microcavity and optimizing the cavity design, we further demonstrate a high-performance ultrastrongly coupled SY LED with weakly dispersive electroluminescence along LP mode and a maximum external quantum efficiency (EQE) of 2.8%. Finally, we realize an ultrastrongly coupled LET based on vertical integration of a high-mobility ZnO transistor and a SY LED in a microcavity, which enables a large switching ratio, uniform emission in the ZnO pattern, and LP mode emission with a maximum EQE of 2.4%. This vertical LET addresses the difficulties of achieving high emission performance and precisely defining the emission area in typical planar LETs, and opens up the possibility of applying various strongly coupled emitters for advanced polariton devices and high-resolution applications.

SiO x C y thin films were deposited by plasma polymerization. The stress of the deposited SiO x C y thin films can be modified by adjusting the beam current, the anode voltage, and the flow rate of hexamethyldisiloxane (HMDSO) gas and oxygen. Reducing the beam current or increasing the flow rate of HMDSO gas increased the linear/cage structure ratio and turned the stress of the SiO x C y thin films from compressive to tensile. The linear/cage structure ratio can be adjusted by changing the composite parameter, W[FM] c /[FM] m , to control the stress of the deposited plasma polymer films. Multilayers of TiO 2 /SiO 2 /TiO 2 were coated on a SiO x C y plasma polymer film herein, reducing their stress by 70% from 0.06 to 0.018 GPa. The refractive index is 1.55, and the absorption coefficient is less than 10 -4 at 550 nm of the SiO x C y films. Superior optical performances of SiO x C y thin films make their use in optical thin films.