PSCs have two typical configurations, regular (n-i-p) and inverted (p-i-n). So far, the highest reported efficiencies of PSCs have been achieved using the n-i-p configuration with a mesoporous scaffold such as, a TiO 2 layer. [11] The mesoporous n-i-p structure usually requires a high temperature thermal treatment, exhibits severe hysteresis behavior and photo-induced degradation. The planar p-i-n architecture, which has no mesoporous scaffold, has attracted growing attention because it offers low temperature fabrication, much less pronounced hysteresis [12] and high stability with no need for dopants in the charge selective layer, which are known to cause degradation. [13] The p-i-n PSCs have also shown superior compatibility in perovskite based tandem solar cells due to lower parasitic absorption loss in the front contact. [14][15][16] Nevertheless, the maximum PCE of p-i-n PSCs still lags behind that of their n-i-p counterparts. This is predominantly the results of lower open circuit voltage and higher non-radiative recombination losses. [17] These losses are dominated by the interfaces of the charge-selective contacts. Extensive efforts have been devoted to improving these interfacial properties. For instance, approaches using ultrathin but conformal organic Recent advances in perovskite solar cells (PSCs) performance have been closely related to improved interfacial engineering and charge selective contacts. Here, a novel and cost-competitive phenothiazine based, self-assembled monolayer (SAM) as a hole-selective contact for p-i-n PSCs is introduced. The molecularly tailored SAM enables an energetically well-aligned interface with the perovskite absorber, with minimized nonradiative interfacial recombination loss, thus dramatically improving charge extraction/transport and device performance. The resulting PSCs exhibit a power conversion efficiency (PCE) of up to 22.44% (certified 21.81%) with an average fill factor close to 81%, which is among the highest efficiencies reported to date for p-i-n PSCs. The new SAM also demonstrates the outstanding operational stability of the PSC, with increasing PCE from 20.3% to 21.8% during continuous maximum power point tracking under a simulated 1 sun illumination for 100 h. The reported findings highlight the great potential of engineered SAMs for the fabrication of stable and high performing PSCs.

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