Highly Efficient Hole Transport Layer‐Free Low Bandgap Mixed Pb–Sn Perovskite Solar Cells Enabled by a Binary Additive System

Abstract

The development of high‐performance hole transport layer (HTL)‐free perovskite solar cells (PSCs) with a simplified device structure has been a major goal in the commercialization of PSCs due to the economic advantage of low manufacturing cost. Unfortunately, low bandgap (Eg) mixed Pb–Sn perovskites, which have promising utility for constructing efficient all‐perovskite tandem solar cells, have rarely been explored in simplified HTL‐free device configurations. In this study, efficient band bending and defect engineering at the interface between perovskite and indium tin oxide (ITO) are realized via a binary additive system using copper thiocyanate (CuSCN) and glycine hydrochloride (GlyHCl). Using mixed Pb–Sn perovskites decorated with crystalline p‐type CuSCN, the energy level alignment at the hole extractive interface is modulated in favor of hole extraction, simultaneously increasing hole mobility. Suppressed nonradiative carrier recombination in the perovskite bulk, or across the charge extractive interface, is further achieved by GlyHCl without disturbing the efficient hole transfer characteristics. Notably, a more optimized band alignment is achieved at the hole extractive interface with the addition of GlyHCl. The HTL‐free mixed Pb–Sn PSC shows an efficiency up to 20.1% under forward bias with negligible hysteresis, comparable to state‐of‐the‐art high‐performance full‐structured mixed Pb–Sn PSCs.

Rubidium Iodide-Doped Spiro-OMeTAD as a Hole-Transporting Material for Efficient Perovskite Photodetectors

“…The significantly decreased trap density reveals that the device with HTL incorporating RbI has a lower trap density than that of the original one. The charge carrier mobilities were obtained in the space charge-limited region, in which the current is proportional to the square of the voltage ( n = 2) using the Mott–Gumey law , Carrier mobilities μ of PD1 and PD3 were calculated as 5.4 × 10 –5 and 2.7 × 10 –3 cm 2 v –1 s –1 , which confirmed the accelerated hole transfer due to RbI.…”

Oxidation of Spiro-OMeTAD in High-Efficiency Perovskite Solar Cells

“…More recently, an increasing number of publications have been dedicated to the development of HTL-free PSC devices, − because they not only constitute a cost-effective technique due to material cost reduction, but also because of their easy configuration with a reduced number of the device layers . In addition, these devices have the advantage of easy film formation, thermal and light stability, and good hole mobility.…”

Molecular design for perovskite solar cells

“…The indium tin oxide (ITO) is a flexible transparent conducting substrate that significantly affects the perovskite device performance. On the other hand, developing high‐performance HTL‐free perovskite solar cells with simpler device configuration is desirable for the perovskite solar cell commercialization 331‐334 . To this end, various interfacial engineering approaches such as the deployment of self‐assembled monolayers have been developed to modify the work function, surface energy, and wettability of the perovskite/ITO interface.…”

“…On the other hand, developing high-performance HTL-free perovskite solar cells with simpler device configuration is desirable for the perovskite solar cell commercialization. [331][332][333][334] To this end, various interfacial engineering approaches such as the deployment of self-assembled monolayers have been developed to modify the work function, surface energy, and wettability of the perovskite/ITO interface. The organic molecules include phosphonic acids, carboxylic acids, and silanes, to name a few, have been demonstrated to interact with the ITO substrate via hydroxylinduced dehydration.…”