Current-density-voltage (J-V) hysteresis in perovskite solar cells (PSCs) is a critical issue because it is related to power conversion efficiency and stability. Although parameters affecting the hysteresis have been already reported and reviewed, little investigation is reported on scan-direction-dependent J-V curves depending on perovskite composition. This review investigates J-V hysteric behaviors depending on perovskite composition in normal mesoscopic and planar structure. In addition, methodologies toward hysteresis-free PSCs are proposed. There is a specific trend in hysteresis in terms of J-V curve shape depending on composition. Ion migration combined with nonradiative recombination near interfaces plays a critical role in generating hysteresis. Interfacial engineering is found to be an effective method to reduce the hysteresis; however, bulk defect engineering is the most promising method to remove the hysteresis. Among the studied methods, KI doping is proved to be a universal approach toward hysteresis-free PSCs regardless of perovskite composition. It is proposed from the current studies that engineering of perovskite film near the electron transporting layer (ETL) and the hole transporting layer (HTL) is of vital importance for achieving hysteresis-free PSCs and extremely high efficiency.

On the Current-Voltage Hysteresis in Perovskite Solar Cells: Dependence on Perovskite Composition and Methods to Remove Hysteresis

Improving charge extraction and suppressing charge recombination are critically important to minimize the loss of absorbed photons and improve the device performance of polymer solar cells (PSCs). In this work, highly efficient PSCs are demonstrated by progressively improving the charge extraction and suppressing the charge recombination through the combination of side‐chain engineering of new nonfullerene acceptors (NFAs), adopting ternary blends, and introducing volatilizable solid additives. The 2D side chains on BTP‐Th induce a certain steric hindrance for molecular packing and phase separation, which is mitigated by fluorination of side chains on BTP‐FTh. Moreover, by introducing two highly crystalline molecules as the second acceptor and volatilizable solid additive, respectively, into the BTP‐FTh‐based host blend, the molecular crystallinity is significantly improved and the blend morphology is finely optimized. As expected, enhanced charge extraction and suppressed charge recombination are progressively realized, contributing to the largely improved fill factor (FF) of the resultant devices. Accompanied by the enhanced open‐circuit voltage (Voc) and short‐circuit current density (Jsc), a record high power conversion efficiency (PCE) of 19.05% is realized finally.

Realizing 19.05% Efficiency Polymer Solar Cells by Progressively Improving Charge Extraction and Suppressing Charge Recombination

Because interfacial nonradiative recombination (NRR) has a significant influence on device performance, the minimization of interfacial NRR losses through interface engineering especially for perov...

Materials and Methods for Interface Engineering toward Stable and Efficient Perovskite Solar Cells

A Review on Additives for Halide Perovskite Solar Cells

Due to their outstanding optoelectronic properties, metal halide perovskites have been intensively studied in recent years. The latest certificated efficiency of 23.3% recently achieved in perovskite solar cells (PVSCs) enables them to be used as a very promising candidate for next-generation photovoltaics. The morphology, defect density, and water resistance of perovskite films have an enormous impact on the performance and stability of PVSCs. Ligands, with coordinating capability, have been widely developed to improve the quality and stability of perovskite materials significantly. In the first section of this review, the role of ligands in fabricating perovskite films by different methods (one-step, two-step, and postdeposition treatment) is discussed. In the second section, the progress on ligand-passivated perovskites via post-treatment, in situ passivation during perovskite formation, and modifying the substrates before perovskite formation is reviewed. In the third section, a discussion of ligand-stabilized perovskite films from the perspectives of crystal crosslinking, dimensionality engineering, and interfacial modification is presented. Finally, a summary and an outlook are given.

Perovskite Photovoltaics: The Significant Role of Ligands in Film Formation, Passivation, and Stability.

Ionic Additive Engineering Toward High‐Efficiency Perovskite Solar Cells with Reduced Grain Boundaries and Trap Density

Chlorinated Fullerene Dimers for Interfacial Engineering Toward Stable Planar Perovskite Solar Cells with 22.3% Efficiency

Cold-Aging and Solvent Vapor Mediated Aggregation Control toward 18% Efficiency Binary Organic Solar Cells

An n-type helical molecule perylene diimide (PDI2) has been explored as an efficient interfacial layer between TiO2 and perovskite for the preparation of perovskite solar cells. The extended π-conjugation of PDI2 ensures a high electron conductivity for efficient charge transport, and the oxygen atoms of the carbonyl groups can chelate with uncoordinated Pb2+ to passivate the surface defects of perovskite crystals. It thereby suppresses interfacial recombination, enhances efficiency, and reduces hysteresis and the light-soaking instability. The power conversion efficiency (PCE) of our perovskite solar cells showed negligible dependence on the thickness of the PDI2 interlayer, and the champion device achieved a high PCE of 19.84% and the hysteresis value (ΔPCE) was reduced to 2.34% compared to 6.46% in the perovskite device without the presence of the PDI2 interlayer.

Restrained light-soaking and reduced hysteresis in perovskite solar cells employing a helical perylene diimide interfacial layer

CsPbX3 nanocrystal (NC)-based blue perovskite light-emitting diodes (PeLEDs) are still in a backward position while their green and red counterparts have achieved significant progress in the past f...

Pang Wang

Papers

Ionic Additive Engineering Toward High‐Efficiency Perovskite Solar Cells with Reduced Grain Boundaries and Trap Density

Chlorinated Fullerene Dimers for Interfacial Engineering Toward Stable Planar Perovskite Solar Cells with 22.3% Efficiency

Cold-Aging and Solvent Vapor Mediated Aggregation Control toward 18% Efficiency Binary Organic Solar Cells

Restrained light-soaking and reduced hysteresis in perovskite solar cells employing a helical perylene diimide interfacial layer

Spectral Tuning of Efficient CsPbBrxCl3–x Blue Light-Emitting Diodes via Halogen Exchange Triggered by Benzenesulfonates