Maze‐Like Halide Perovskite Films for Efficient Electron Transport Layer‐Free Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) without an electron transport layer (ETL) exhibit fascinating advantages such as simplified configuration, low cost, and facile fabrication process. However, the performance of ETL‐free PSCs has been hampered by severe charge carrier recombination induced either by current leakage (insufficient perovskite film coverage) or inferior charge extraction. Herein, an additive‐assisted morphological engineering strategy is used to construct an intriguing bilayer perovskite film featuring a dense bottom layer and a maze‐like top layer. Such maze‐like perovskite films enable the construction of ETL‐free PSCs with a PCE of 18.5% and negligible hysteresis, which can be attributed to the higher crystallinity and superior light‐harvesting capability of the resultant perovskite film, as well as facilitated hole extraction at the hole transport layer (HTL)/perovskite interface. This work provides a simple approach to modify the perovskite film morphology and demonstrates the correlation between facilitated charge‐carrier extraction and high‐performance ETL‐free perovskite photovoltaics.

The Rise of Textured Perovskite Morphology: Revolutionizing the Pathway toward High‐Performance Optoelectronic Devices

“…Very recently, we demonstrated a perovskite with an innovative maze‐like morphology (Figure c) through the inclusion of a large amount of methylammonium chloride (MACl) in the perovskite ink. The maze‐like perovskite film shows great potential to enlarge the interfacial contact with charge‐selective layers for boosted charge extraction . The growth mechanism of this intriguing perovskite film is possibly the product of slowed‐down nucleation and crystallization of the perovskite ink and the formation of an intermediate phase incorporating chlorine.…”

“…Copyright 2018, Nature Publishing Group. Figure (i) is reproduced with permission . Copyright 2019, Wiley‐VCH.…”

Simple, Robust, and Going More Efficient: Recent Advance on Electron Transport Layer‐Free Perovskite Solar Cells

“…With the optimized parameters, a highest PCE of 19.16% was demonstrated, pointing out the great potential of ETL-free PSCs in term of device performance enhancement. [114] Copyright 2019, Wiley-VCH. [93,102] Under the drift-diffusion equation framework, Choy and co-workers have explored the way to approach the efficiency limit and found that the PSC performance cannot be significantly improved by only inserting one blocking layer.…”

Recent Progress in High‐efficiency Planar‐structure Perovskite Solar Cells

“…[61] Wang et al added MACl to perovskite precursor to improve crystallinity, enhance light-harvesting ability, and improve carrier separation and extraction at HTL/perovskite interface. [62] In HTL-free PSCs of inverted structure, Jen et al firstly demonstrated an inverted HTL-free PSC with the structure ITO/MAPbI 3 /PCBM/ Bis-C60 (C60-bisadduct)/Ag, a PCE of 11.02%, and a high Voc of 1.01 V was achieved in 2015. [62] In HTL-free PSCs of inverted structure, Jen et al firstly demonstrated an inverted HTL-free PSC with the structure ITO/MAPbI 3 /PCBM/ Bis-C60 (C60-bisadduct)/Ag, a PCE of 11.02%, and a high Voc of 1.01 V was achieved in 2015.…”

“…You and co-workers found that the best PCE of PSCs could be obtained while the residual PbI 2 is moderate, even though large amount of excess PbI 2 can still show good PCE in reverse scan; however, the devices showed poor photostability and significant hysteresis. [62] Copyright 2019, John Wiley & Sons. [19] Recently, Zhao et al also used PbI 2 to passivate both sides of the perovskite layer and deliver stabilized PCE of 22% with a high Voc of 1.15 V. [68] [6] PEDOT:PSS 18% 20.11 1.11 80.6 [53] rGO/PTAA 17.2% 20.3 1.09 77.7 [56] PTAA:F4-TCNQ [49] Cu:NiO x 20.14 23.07 1.12 77.06 [48] Figure 10.…”