BiI3 is an n-type semiconductor synthesized in thin layers. Although the material has favorable optoelectronic properties, its efficiency (PCE) does not contend with silicon. To address this, we optimized the layers. The BiI3 cell contained the following layers, in order: Glass/FTO/TiO2/BiI3/ P3HT/Gold, where we optimized the BiI3 and TiO2 layers. We optimized the TiO2 layer through an additional mesoporous layer and optimized the overall interlayer contact through a 10 minute 100°C post-anneal, improving the JSC and VOC, respectively. We oxidized the BiI3 layer and increased the grain size via solvent vapor annealing in DMF, improving VOC, and supported this finding through computational modeling. Achieving a PCE of 0.23%, we affirm that BiI3 is a promising material
