All-inorganic CsPbI₃ perovskite quantum dots have received substantial research interest for photovoltaic applications because of higher efficiency compared to solar cells using other quantum dots materials and the various exciting properties that perovskites have to offer. These quantum dot devices also exhibit good mechanical stability amongst various thin-film photovoltaic technologies. We demonstrate higher mechanical endurance of quantum dot films compared to bulk thin film and highlight the importance of further research on high-performance and flexible optoelectronic devices using nanoscale grains as an advantage. Specifically, we develop a hybrid interfacial architecture consisting of CsPbI₃ quantum dot/PCBM heterojunction, enabling an energy cascade for efficient charge transfer and mechanical adhesion. The champion CsPbI₃ quantum dot solar cell has an efficiency of 15.1% (stabilized power output of 14.61%), which is among the highest report to date. Building on this strategy, we further demonstrate a highest efficiency of 12.3% in flexible quantum dot photovoltaics.

Rational hole transport layer (HTL) material design is regarded as one of the most important approaches to improve the efficiency and stability of perovskite solar cells (PSCs). Herein, we investigate the effect of a widely spread p-type dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) on the optical and electrical properties of conventional poly(3,4-ethylenedioxythiophene):poly-(styrene sulfonate) (PEDOT:PSS) HTLs, as well as the photovoltaic performance of the corresponding perovskite solar cells. Doping F4-TCNQ at a low concentration can efficiently adjust the electrical properties of the PEDOT:PSS film and lower the highest occupied molecular orbital (HOMO) level. As a result, the enhanced electrical conductivity and energetically favorable energy level alignment of the doped film allow efficient carrier transport from the perovskite absorber layer to the HTL. Finally, the PSCs with the F4-TCNQ doped HTL exhibited simultaneously increased short-circuit current (J_sc), open circuit voltage (V_oc) and fill factor (FF). The highest power conversion efficiency (PCE) was notably improved from 13.30% (undoped) to 17.22% (0.30 wt% of F4-TCNQ doping), suggesting that the F4-TCNQ doped PEDOT:PSS film is an efficient HTL to achieve high performance perovskite solar cells.