Highly Stable and Efficient Perovskite Solar Cells with 22.0% Efficiency Based on Inorganic–Organic Dopant‐Free Double Hole Transporting Layers

Abstract

Most of the high performance in perovskite solar cells (PSCs) have only been achieved with two organic hole transporting materials: 2,2′,7,7′-tetrakis(N,Ndi-p-methoxyphenylamine)-9,9-spirobifluorene (Spiro-OMeTAD) and poly(triarylamine) (PTAA), but their high cost and low stability caused by the hygroscopic dopant greatly hinder the commercialization of PSCs. One effective alternative to address this problem is to utilize inexpensive inorganic hole transporting layer (i-HTL), but obtaining high efficiency via i-HTLs has remained a challenge. Herein, a well-designed inorganic-organic double HTL is constructed by introducing an ultrathin polymer layer dithiophene-benzene (DTB) between CuSCN and Au contact. This strategy not only enhances the hole extraction efficiency through the formation of cascaded energy levels, but also prevents the degradation of CuSCN caused by the reaction between CuSCN and Au electrode. Furthermore, the CuSCN layer also promotes the formation of a pinhole-free and compact DTB over layer in the CuSCN/DTB structure. Consequently, the PSCs fabricated with this CuSCN/DTB layer achieves the power conversion efficiency of 22.0% (certified: 21.7%), which is among the top efficiencies for PSCs based on dopant-free HTLs. Moreover, the fabricated PSCs exhibit high light stability under more than 1000 h of light illumination and excellent environmental stability at high temperature (85 °C) or high relative humidity (>60% RH).

A brief review of hole transporting materials commonly used in perovskite solar cells

“…So far, spiro-OMeTAD is still the most popular HTM for high-performing PSCs, but it only works effectively in combination with some additives, for example, 4-tert-butylpyridine (tBP) and bis (trifluoromethane) sulfonimide lithium salt (Li-TFSI) [25]. Dopant-free HTMs such as PEDOT:PSS [poly (3,4-ethylenedioxythiophene): polystyrene sulfonate] and P3HT [poly(3-hexylthiophene-2,5-diyl)] have also been developed [26][27][28][29]. Our group also reported a dopant-free P1-based PSCs which achieved a PCE of 18.30% [30].…”

Simultaneous Improvement of the Power Conversion Efficiency and Stability of Perovskite Solar Cells by Doping PMMA Polymer in Spiro‐OMeTAD‐Based Hole‐Transporting Layer

“…[ 3–6 ] Generally, two kinds of structures or regular n−i−p or inverted p−i−n are adopted in PSCs, where n/p and i stand for electron‐/hole‐transporting layer (ETL/HTL) and perovskite, respectively. [ 7,8 ] As for HTL, several materials have been tried, like CuI, [ 9 ] CuSCN, [ 10 ] poly(3,4‐ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT:PSS), [ 11 ] poly (3‐hexylthiophene) (P3HT), [ 12 ] polytriarylamine (PTAA), [ 13 ] 2,2′,7,7′‐tetrakis [ N , N ‐di (4‐methoxyphenyl) amino]‐9,9′‐spiro‐bifluorene (spiro‐OMeTAD). [ 14 ] Among these HTLs, spiro‐OMeTAD is adopted in most.…”

Recent Progress in Perovskite Solar Cells Modified by Sulfur Compounds

“…d) EIS of CuSCN, DTB, and CuSCN/DTB-based PSCs, inset image shows equivalent fitting circuit. Reproduced with permission [98]. Copyright 2020, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.…”