Passivating surface and bulk defects of perovskite films has been proven to be an effective way to minimize nonradiative recombination losses in perovskite solar cells (PVSCs). The lattice interference and perturbation of atomic periodicity at the perovskite surfaces often significantly affect the material properties and device efficiencies. By tailoring the terminal groups on the perovskite surface and modifying the surface chemical environment, the defects can be reduced to enhance the photovoltaic performance and stability of derived PVSCs. Here, we report a rationally designed bifunctional molecule, piperazinium iodide (PI), containing both R 2 NH and R 2 NH 2 + groups on the same six-membered ring, behaving both as an electron donor and an electron acceptor to react with different surface-terminating ends on perovskite films. The resulting perovskite films after defect passivation show released surface residual stress, suppressed nonradiative recombination loss, and more n-type characteristics for sufficient energy transfer. Consequently, charge recombination is significantly suppressed to result in a high open-circuit voltage (V OC ) of 1.17 V and a reduced V OC loss of 0.33 V. A very high power conversion efficiency (PCE) of 23.37% (with 22.75% certified) could be achieved, which is the highest value reported for inverted PVSCs. Our work reveals a very effective way of using rationally designed bifunctional molecules to simultaneously enhance the device performance and stability.

The non-radiative energy losses at both top and bottom interfaces of perovskite were simultaneously suppressed by introducing LAIs between the hole transport layer and perovskite layer. More importantly, the LAIs have also effectively inhibited the phase segregation on the perovskite surface, enabling homogeneous surface properties. As a result, a champion efficiency of over 22% was realized for p-i-n structured PVSCs, which is among the highest efficiencies reported for p-i-n structured PVSCs.

Perovskite solar cells (PSCs) are ideally fabricated entirely via a scalable solution process at low temperatures to realize the promise of simple manufacturing, low‐cost processing, compatibility with flexible substrates, and perovskite‐based tandem solar cells. However, high‐quality photoactive perovskite thin films under those processing conditions is a challenge. Here, a laminar air‐knife‐assisted room‐temperature meniscus coating approach that enables one to control the drying kinetics during the solidification process and achieve high‐quality perovskite films and solar cells is devised. Moreover, this approach offers a solid model platform for in situ UV–vis and microscopic investigation of the perovskite film drying kinetics, which provide rich insights correlating the degree of supersaturation, the nucleation, and growth rate during the kinetic drying process, and ultimately, the film morphology and performance of the solar cell devices. Manufacturing friendly, antisolvent‐free room‐temperature coating of hysteresis‐free PSCs with a power conversion efficiency of 20.26% for 0.06 cm2 and 18.76% for 1 cm2 devices is demonstrated.

Currently,the performance improvement for inverted perovskite solar cells (PVSCs) is mainly limited by the high open circuit voltage (V OC)l oss caused by detrimental nonradiative recombination (NRR) processes.H erein, we report as imple and efficient wayt os imultaneously reduce the NRR processes inside perovskites and at the interface by rationally designing an ew pyridine-based polymer hole-transporting material (HTM), PPY2,w hiche xhibits suitable energy levels with perovskites,high hole mobility,effective passivation of the uncoordinated Pb 2+ and iodide defects,aswell as the capability of promoting the formation of high-quality polycrystalline perovskite films.I na bsence of any dopants,t he inverted PVSCs using PPY2 as the HTM deliver an encouraging PCE up to 22.41 %w ith as mall V OC loss (0.40 V), among the best device performances for inverted PVSCs reported so far. Furthermore, PPY2-based unencapsulated devices showa n excellent long-term photostability,a nd over 97 %o fits initial PCE can be maintained after one sun constant illumination for 500 h.

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