Fabrication of Highly Efficient and Stable Hole-Transport Material-Free Perovskite Solar Cells through Morphology and Interface Engineering: Full Ambient Process

Carbon-based hole-transport material (HTM)-free perovskite solar cells (PVSCs) with low cost and high stability attract research interest. Herein, a facile way to improve the performance of HTM-free PVSCs by employing two strategies is reported: first, adding a small amount of tetrahydrofuran (THF) in lead iodide (PbI2)/N,N-dimethylformamide (DMF) solution to improve the quality of the perovskite film; second, introducing an ultra-thin Al2O3 film at the interface of TiO2/perovskite to reduce charge recombination. THF is found to facilitate the formation of homogenous perovskite films with better coverage, while the ultra-thin Al2O3 layer avoids the direct contact of TiO2 with CH3NH3PbI3. The Al2O3 layer can effectively block holes and prevent charge recombination, thus leading to a dramatic improvement of open-circuit voltage and fill factor in PVSCs. Moreover, the PVSCs show excellent long-term stability with no degradation for 1000 h under ambient conditions. A facile way for the future commercialization of efficient low-cost HTM-free PVSCs is provided.