Dopant‐Free Crossconjugated Hole‐Transporting Polymers for Highly Efficient Perovskite Solar Cells

Abstract

Currently, there are only very few dopant-free polymer hole-transporting materials (HTMs) that can enable perovskite solar cells (PVSCs) to demonstrate a high power conversion efficiency (PCE) of greater than 20%. To address this need, a simple and efficient way is developed to synthesize novel crossconjugated polymers as high performance dopant-free HTMs to endow PVSCs with a high PCE of 21.3%, which is among the highest values reported for single-junction inverted PVSCs. More importantly, rational understanding of the reasons why two isomeric polymer HTMs (PPE1 and PPE2) with almost identical photophysical properties, hole-transporting ability, and surface wettability deliver so distinctly different device performance under similar device fabrication conditions is manifested. PPE2 is found to improve the quality of perovskite films cast on top with larger grain sizes and more oriented crystallization. These results help unveil the new HTM design rules to influence the perovskite growth/crystallization for improving the performance of inverted PVSCs.

Modifying Surface Termination of CsPbI3 Grain Boundaries by 2D Perovskite Layer for Efficient and Stable Photovoltaics

“…The organic–inorganic halide perovskites have emerged as very promising semiconductors owing to their excellent optoelectronic properties and low‐cost fabrication. [ 1–5 ] In the past decade, the power conversion efficiencies (PCEs) of perovskite solar cells (PVSCs) have dramatically soared from initial 3.8% to as high as 25.5%, which is comparable to that of silicon based solar cells. [ 6,7 ] Nevertheless, the long‐term stability of these perovskites and their derived solar cells under external stimuli (such as heat, moisture, and illumination) still needs to be significantly improved in order to facilitate their commercialization.…”

Efficient Inverted Perovskite Solar Cells with Low Voltage Loss Achieved by a Pyridine‐Based Dopant‐Free Polymer Semiconductor

“…As well demonstrated, the HTL in inverted PVSCs plays a critical role in the crystallization process of perovskite film, [69–71] which in turn affects the NRR within the perovskite bulk. The X‐ray powder diffraction (XRD) patterns were then collected to evaluate the quality of the perovskite films grown atop PPY2 and PTAA HTL.…”

“…Moreover,the shortened decay time for bilayered perovskite/ PPY1 compared to that from PTAA could be due to its relatively higher hole mobility. [67,68] As well demonstrated, the HTL in inverted PVSCs plays ac ritical role in the crystallization process of perovskite film, [69][70][71] which in turn affects the NRR within the perovskite bulk. TheX -ray powder diffraction (XRD) patterns were then collected to evaluate the quality of the perovskite films grown atop PPY2 and PTAA HTL.…”

Fused Furan‐Based Organic Small Molecules as Dopant‐Free Hole Transporting Material for Inverted Perovskite Solar Cells

“…In this context, organic small molecules are good candidates because of low‐temperature processability, no batch‐to‐batch variation, and ease of tailoring. [ 11–16 ] The excellent small‐molecule HTM candidate in inverted devices should meet but not be limited to the following properties: matched energy level with perovskites, high hole mobility, and poor solubility in DMF and/or DMSO. The fused furan derivative of 2,7‐is(4‐octylphenyl)naphtho [2,1‐b:6,5‐b′]difuran (C 8 ‐DPNDF, Figure a) shows a hole mobility up to 3.6 cm 2 V − 1 s − 1 , which is much higher than the HTMs utilized in PSCs.…”