Solar cells are instrumental to efforts to develop environmentally friendly power sources. Solar cells based on hybrid organic/inorganic materials have achieved performance levels comparable to commercial devices. Properties such as low-cost processing and flexibility make them an attractive alternative to silicon. However, improving the performance of hybrid solar cells has been limited by current fabrication and characterization strategies. The PIs have shown that these materials can be electrochemically doped by a liquid without dissolving them. This liquid approach yields a toolkit that can be used to measure and enhance intrinsic electrical properties. This liquid toolkit will be used to modify and enhance hybrid solar cells. The PIs will identify promising materials combinations for hybrid solar cells by computer modeling. Thin films will be prepared, characterized, and optimized for solar cells. Hybrid solar cells will be fabricated and characterized for solar power conversion and stability. Additional studies will identify causes of degradation. These efforts will further the potential of hybrid solar cells to transform the solar energy landscape. The proposed effort will involve education and outreach activities to broaden participation of underrepresented groups, engage the public, and train the next generation of scientists and engineers in renewable energy. Texas State University is a Hispanic Serving Institution. The proposed project will leverage this talent pool to increase diversity in research and STEM education.
The PIs will electrically dope and characterize hybrid perovskite (HP) thin films and solar cell devices using a recently-developed solvent toolkit. This solvent toolkit is based on a hydrofluoroether (HFE) solvent system that is nondestructive to HPs and permits electrochemical characterization and modification of HP thin films. To produce p and n doped devices of favorable electrical and optical performance, the project team will utilize three approaches to identify optimal device compositions from the wide range of possible devices afforded by the solvent toolkit technique. To characterize the broad potential experimental landscape, numerical modeling with density functional theory (DFT) will be performed, identifying favorable doping mixtures. Subsequently, electrochemical study of thin HP films in HFE electrolytes will be performed to experimentally achieve doping effects such as improved conductivity and new energy levels. Finally, HP solar cells will be fabricated from doping strategies motivated by electrochemical study, and carefully characterized for efficiency, structure and stability. More specifically, we will utilize DFT with Hubbard correction and spin-orbital coupling to investigate the effects of different ionic dopants on the band structure, bandgap, doping energy levels, loss of inversion symmetry, Rashba effect, spin texture, electron-phonon coupling, and quantum confinement of HP materials. Electrochemical (EC) doping will be accomplished in HFE solvents with chronopotentiometry and chronoamperometry and characterized with cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy with custom multiplexed chips. HP solar cell devices will be fabricated from films doped by HFE processing and tested for efficiency and lifetime metrics. We will subsequently investigate how the EC doping of HP films affects device performance and stability while the device is being stressed with light and temperature cycles. We will correlate changes in HP-PV device parameters (power conversion efficiency, short-circuit current, open-circuit voltage, filling factor, hysteresis, etc.) with structural, chemical, and optical properties as the device undergoes controlled aging in the air-free atmosphere.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
