electron-accepting TiO 2 scaffolds require a high-temperature annealing process (≈500 °C), which limits their use with flexible substrates. Planar heterojunctionstructured PSCs have also been widely investigated because they enable adoption of low-temperature electron accepting layers (EALs). Zinc oxide, ZnO, is a strong EAL candidate because it offers good electrical properties even when prepared at low temperatures. [12][13][14][15][16] However, ZnO is used less often than mesoporous TiO 2 because it has several drawbacks. The surface properties of the ZnO layers are not favorable for growth of uniform perovskite layers with large crystal grains. This affects device performance significantly. [2,3,[7][8][9][10]17] Thus, efforts have been undertaken to improve perovskite layer quality by enhancing ZnO surface hydrophobicity. [18][19][20][21] Another shortcoming is the reverse reaction from perovskite to PbI 2 that can occur at ZnO/perovskite interfaces during perovskite layer formation. [14,[22][23][24] Two-step sequential deposition method has been employed to fabricate perovskite active layers on ZnO-EALs. This results in more reproducible synthesis of continuous, pinholefree perovskite layers than conventional single deposition methods. [15,21,[25][26][27][28][29] The perovskite layers in these reports were formed in two steps: (i) PbI 2 layer formation and (ii) perovskite layer formation, which occurred when the PbI 2 layer was immersed into an alkyl-ammonium iodide solution and annealed (80-100 °C). The sequential deposition method partially alleviated the burden of the reverse reaction that occurs at ZnO/perovskite interfaces, while helping to achieve a PCE of ≈16%. [15,30] Thus, the development of these strategies may offer a chance to further enhance low-temperature ZnO based PSC performance.Herein, we present high-efficiency, low-temperature PSCs using a strategy that combines self-assembled monolayer (SAM) modification of ZnO-EALs with sequential preparation of perovskite active layers. SAMs of the newly synthesized, highly polar molecules were constructed on ZnO-EALs and the perovskite layers were formed via sequential deposition. The SAMs acted as ZnO wetting control layers and as electric dipole layers. [1,13,19,20,[31][32][33] Modifying our SAMs enhanced the hydrophobicity of ZnO, which improved perovskite formation quality. Simultaneously, the electric dipole effect induced via Herein, this study reports high-efficiency, low-temperature ZnO based planar perovskite solar cells (PSCs) with state-of-the-art performance. They are achieved via a strategy that combines dual-functional self-assembled monolayer (SAM) modification of ZnO electron accepting layers (EALs) with sequential deposition of perovskite active layers. The SAMs, constructed from newly synthesized molecules with high dipole moments, act both as excellent surface wetting control layers and as electric dipole layers for ZnO-EALs. The insertion of SAMs improves the quality of PbI 2 layers and final perovskite layers during sequential dep...

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Ternary organic photovoltaic (OPV) devices with multiple light-absorbing active materials have emerged as an efficient strategy for realizing further improvements in the power conversion efficiency (PCE) without building complex multijunction structures. However, the third component often acts as recombination centers and, hence, the optimization of ternary blend morphology poses a major challenge to improving the PCE of these devices. In this work, the performance of OPVs is enhanced through the morphological modification of nonfullerene acceptor (NFA)-containing binary active layers. This modification is achieved by incorporating fullerenes into the layers. The uniformly dispersed fullerenes are sufficiently continuous and successfully mediate the ordering of NFA without charge or energy transfer. Owing to the simultaneous improvement in the charge generation and extraction, the PCE (12.1%) of these parallel-linked ternary devices is considerably higher than those of the corresponding binary devices (9.95% and 7.78%). Moreover, the additional energy loss of the ternary device is minimized, compared with that of the NFA-based binary device, due to the judicious control of the effective donor:acceptor composition of the ternary blends.

The susceptibility of porphyrin derivatives to light‐harvesting and charge‐transport operations have enabled these materials to be employed in solar cell applications. The potential of porphyrin derivatives as hole‐transporting materials (HTMs) for perovskite solar cells (PSCs) has recently been demonstrated, but knowledge of the relationships between the porphyrin structure and device performance remains insufficient. In this work, a series of novel zinc porphyrin (PZn) derivatives has been developed and employed as HTMs for low‐temperature processed PSCs. Key to the design strategy is the incorporation of an electron‐deficient pyridine moiety to down‐shift the HOMO levels of porphyrin HTMs. The porphyrin HTMs incorporating diphenyl‐2‐pyridylamine (DPPA) have HOMO levels that are in good agreement with the perovskite active layers, thus facilitating hole transfers from the perovskite to the HTMs. The DPPA‐containing zinc porphyrin‐based PSCs gave the best performance, with efficiency levels comparable to those of PSCs using spiro‐OMeTAD, a current state‐of‐the‐art HTM. In particular, PZn–DPPA‐based PSCs show superior air stability, in both doped and undoped forms, to spiro‐OMeTAD based devices.

Fullerene-free all-small-molecule organic photovoltaic cells (SM-OPVs) have attracted considerable attention because of well-defined molecular structures with low batch-to-batch variation. Porphyrin derivatives have recently emerged as one of the promising conjugated building blocks for the small-molecule (SM) donors. Herein, we first report fullerene-free SM-OPVs employing porphyrin-based donors. Three zinc porphyrin (PZn)-based SM donors, which have strong bimodal absorption in the visible region and near-infrared region, are synthesized. Constructing bulk-heterojunction (BHJ) active layers using the PZn donors and a SM acceptor, IDIC, which have complementary absorption, achieved panchromatic photon-to-current-conversion from 400 to 900 nm. The manipulation of side chains in the PZn donors considerably influenced the molecular ordering and nanomorphology of the BHJ active layers. PZn-based fullerene-free SM-OPV devices with promising power conversion efficiency of 6.13% were achieved, which also offers crucial guidance for developing fullerene-free OPVs using porphyrin derivatives.

In article number https://doi.org/10.1002/aenm.201701683, In Hwan Jung, Sung‐Yeon Jang, and co‐workers report the synthesis of ‘high‐efficiency low‐temperature processed perovskite solar cells’ by the combination of two techniques; the modification of solution‐processed ZnO using a self‐assembled monolayer, and the fabrication of perovskite layers by a sequential deposition method. This technique may pave the way to efficiently reducing the processing temperature of perovskite solar cells.