Highly efficient air-stable/hysteresis-free flexible inverted-type planar perovskite and organic solar cells employing a small molecular organic hole transporting material

Abstract

To acknowledge exceptionally productive flexible perovskite solar cells, low-temperature-processable efficient organic hole transporting materials are very significant for the emerging photovoltaic research. A new organic small molecular hole transporting material (N-(4-(9H-carbazol-9-yl)phenyl)-7-(4-(bis(4-methoxyphenyl)amino)phenyl)-N-(7-(4-(bis(4-methoxyphenyl)amino)phenyl)-9,9-dioctyl-9H-fluoren-2-yl)-9,9-dioctyl-9H-fluoren-2-amine (CzPAF-TPA)) has been rationally designed and synthesized for both highly efficient solution-processed flexible and rigid inverted-type planar heterojunction perovskite solar cells (i-PSCs) and flexible and rigid bulk heterojunction inverted organic solar cells (BHJ IOSCs). The dopant-free CzPAF-TPA-based device displayed significantly improved device performance in solution-processed flexible i-PSCs and flexible BHJ IOSCs with power conversion efficiencies (PCEs) of 12.46% and 7.52%, respectively, with negligible hysteresis, which is superior to that of standard HTM. Furthermore, the high PCE was recorded on rigid ITO substrate in dopant-free i-PSCs (PCE ~ 15.71%) and BHJ IOSCs (PCE ~ 8.74%). Notably, the promising technique of flash-photolysis time-resolved microwave conductivity was also well correlated with the obtained results. In addition to their high device performance in flexible as well as rigid i-PSCs and flexible BHJ IOSCs, they also showed long-term stability over 500h and 30 days with minimal loss of initial performance.