Unveiling the effect of carbon dots on the TiO2-involved electron transport in perovskite solar cells

Hydrothermal-synthesized TiO2 was verified to effectively replace the commercial dyesol-TiO2 as the electron transport layer for promising perovskite devices. Still, the electron transport ability of this TiO2 is restricted by the surface defects. Herein, orange carbon dots prepared from p-phenylenediamine were employed as modifiers to regulate the TiO2-involved electron transport in perovskite solar cells. The results show that an appropriate amount of CDs can effectively reduce interface electron recombination, TiO2-CDs layers can improve the lattice growth of subsequent perovskite and result in efficient electron extraction from perovskite to TiO2. More importantly, the electron mobility of TiO2 increases from 3.00 × 10−5 to 4.13 × 10−5 cm2·V−1·s−1 due to the addition of CDs. In terms of photovoltaic performance, the photoelectric conversion efficiency reached 21.14% when TiO2-CDs were used as the mesoporous electron transfer layer, which is higher than that of TiO2-based PSCs (17.29%) under the same conditions. Meanwhile, the TiO2-CDs-based PSCs display negligible hysteresis, better stability and repeatability.