Phenanthrenone-based hole transport material for efficient dopant-free perovskite solar cells

Spiro-OMeTAD is the most popular hole transport material (HTM) for perovskite solar cells. The insertion of one carbonyl group into the spirobifluorene framework in spiro-OMeTAD gave a novel phenanthrenone-based hole transport material (spiro-PT-OMeTAD). It is found that the introduction of one carbonyl group into spiro-PTOMeTAD led to a big difference in the absorption behaviors, frontier molecular orbital energy levels and hole mobilities. The steady-state photoluminescence characterization and the space-charge-limited-current measurement indicate that this phenanthrenone-based material plays an important role in hole collection and transportation in perovskite solar cells. As a result, the dopant-free perovskite solar cells based on spiro-PTOMeTAD showed highly improved performance by exhibiting a short-circuit current density of 22.36 mA/cm(2), an open-circuit voltage of 0.99 V, and a fill factor of 0.62% under 1 sun illumination, which gave an overall power conversion efficiency (PCE) of 13.83%, compared to 10.5% for the spiro-OMeTAD based devices.