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Ryan Stoddard

Mixed-halide perovskites with composition APb(I,Br)3 (where A+ = methylammonium, formamidinium, or Cs) are interesting for tandem photovoltaics party because the bandgap can be precisely tuned with the halide composition. However, mixed-halide perovskites with the ideal bandgap (~1.75 eV) for the top cell in a 2-terminal tandem with c-Si or CIGS have shown considerable phase segregation into bromine rich and iodine rich phases under illumination. I hypothesize that phase segregation can be reduced with control of hydrogen bonding and electrostatic interactions within the APb(I,Br)3 structure by using A+ mixtures along with interstitial dopants such as H+, I-, Br-, O2, and Li+. By using high throughput spray coating methods with photoluminescence mapping, phase segregation can be easily identified, and the effect of A+ composition and interstitial dopants can be mechanistically studied. Further benefits of a structure stabilized with interstitial doping would be reduced hysteresis and resistance to degradation.

Advisor Hugh Hillhouse -Chemical Engineering