Crystalline silicon solar cell technology has dominated the photovoltaic technology market for years with a current market share of 90%, owing to its wide technological applications in semiconductor electronics. Light absorption for limited range of the spectrum and thermalization losses hinder further increase in silicon solar cell efficiency. This research endeavor is geared toward increasing efficiency beyond the thermodynamic limits imposed by the physics of single-junction silicon solar cells by incorporation of different bandgap semiconductors in tandem. This research will perform optical and electronic optimization schemes to improve absorption, photocurrent and efficiency in solar cells, light emitting diodes and other electronic devices. The research will address fundamental limitations of integration of perovskites with silicon and other semiconductors and will impact a diverse technical and societal community. The broader impacts of this research lies in 1) incorporating research findings into curriculum enhancement of courses such as Photovoltaic Engineering, Physical Electronics and Optoelectronic Engineering at Tennessee Tech University, 2) recruiting female, underrepresented groups and veterans in research and 3) organizing outreach activities to foster increased awareness of energy technologies at the high-school, middle-school and community levels. This will help increase longer-term enrollment in engineering and computing education, yielding many long-standing benefits to society at large.
The primary scholarship of the research plan lies in addressing the challenges facing perovskite/Si tandem technologies such as: 1) high sub-bandgap absorption in the perovskite absorber; 2) low photoconversion efficiency of perovskite/Si tandem; 3) relatively higher reflection and parasitic losses; and 4) compromising open-circuit voltage and fill factor. Transfer-matrix based optimization of optical absorption, reflection and internal quantum efficiency vs. wavelength of each layer will provide insights about maximum achievable absorption efficiency and photocurrent in each layer. Modeling of wavelength-dependent absorption by combining conventional pyramidal texture with wavelength-selective intermediate reflector will further increase the tandem efficiency. Doping concentration and thickness based current density vs. voltage simulations for each subcell layer in the tandem and optimizing those parameters to match the current will achieve the best possible photoconversion efficiency for tandem designs. This research will have significant contributions to solid-state lighting, lasing and thin-film electronic device applications.
