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.

Inverted type perovskite solar cells (PSCs) have recently emerged as a major focus in academic and industrial photovoltaic research. Their multiple advantages over conventional PSCs include easy processing, hysteresis‐free behavior, high stability, and compatibility for tandem applications. However, the maximum power conversion efficiency (PCE) of inverted PSCs still lags behind those of conventional PSCs because suitable charge‐selective materials for inverted PSCs are limited. In this study, excellent hole‐selective materials for inverted PSCs are introduced. A series of tricyclic aromatic rings containing O, S, or Se, respectively, as a core heteroatom, along with a phosphonic acid anchor, form a self‐assembled monolayer (SAM) that directly contacts the perovskite absorber. The influence of heteroatoms in the aromatic structure on the molecular energetics and operating characteristics of the corresponding inverted PSCs is investigated using complementary experimental techniques as well as density functional theory (DFT) calculations. It is found that all of the SAMs formed an energetically well‐aligned interface with the perovskite absorber. The interaction energy between the Se‐containing SAM and perovskite absorber is the strongest among the series and it reduces the interfacial defect density, in turn leading to an extended charge carrier lifetime. As a result, PSCs incorporating the Se‐containing SAM achieves a PCE of 22.73% and retains ≈96% of their initial efficiency after a maximum power point tracking test of 500 h without encapsulation under ambient conditions. All of the SAMs are then employed in organic solar cells (OSCs). Again, the Se‐containing SAM‐based OSCs demonstrates the highest PCE of 17.9% among the three molecular SAM‐based OSCs. This study demonstrates the great potential for precisely engineered SAMs for use in high‐performance solar cells.

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