High‐Performance Inverted Planar Perovskite Solar Cells Enhanced by Thickness Tuning of New Dopant‐Free Hole Transporting Layer

Abstract

A new hole transporting material (HTM) named DMZ is synthesized and employed as a dopant‐free HTM in inverted planar perovskite solar cells (PSCs). Systematic studies demonstrate that the thickness of the hole transporting layer can effectively enhance the morphology and crystallinity of the perovskite layer, leading to low series resistance and less defects in the crystal. As a result, the champion power conversion efficiency (PCE) of 18.61% with JSC = 22.62 mA cm−2, VOC = 1.02 V, and FF = 81.05% (an average one is 17.62%) is achieved with a thickness of ≈13 nm of DMZ (2 mg mL−1) under standard global AM 1.5 illumination, which is ≈1.5 times higher than that of devices based on poly(3,4‐ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT:PSS). More importantly, the devices based on DMZ exhibit a much better stability (90% of maximum PCE retained after more than 556 h in air (relative humidity ≈ 45%–50%) without any encapsulation) than that of devices based on PEDOT:PSS (only 36% of initial PCE retained after 77 h in same conditions). Therefore, the cost‐effective and facile material named DMZ offers an appealing alternative to PEDOT:PSS or polytriarylamine for highly efficient and stable inverted planar PSCs.

Imide‐Functionalized Triarylamine‐Based Donor‐Acceptor Polymers as Hole Transporting Layers for High‐Performance Inverted Perovskite Solar Cells

“…Fortunately, for inverted PVSCs, this can be attenuated by employing a thin layer of the polymeric HTLs (can be constrained to below 10 nm), as demonstrated in various previous reports. [28] As such, the majority of photons can still reach the perovskite layer in the PVSC devices. For instance, in the current case, the overall transmittance Cyclic voltammetry measurements were carried out to evaluate the FOM energy levels of two polymeric HTLs.…”

A Review on Solution‐Processable Dopant‐Free Small Molecules as Hole‐Transporting Materials for Efficient Perovskite Solar Cells

“…Besides carbazole, another typical tricyclic unit fluorene which is a half of the spiro[bifluorene] core in spiro-OMeTAD was also applied as a building block of SM-HTMs, and almost all of them served in inverted PSCs. [90][91][92][93][94][95][96][97][98] Ding et al [97] constructed an HTM with a fluorene core and two methylthio (MeS)-group modified DPA arms through only two synthetic steps. The MeS group was beneficial for deepening the HOMO level of the molecule than MeO group, and the corresponding device demonstrated a PCE of 19.06%, much improved relative to that of PEDOT:PSS based one with a PCE of only 13.9%.…”

“…The MeS group was beneficial for deepening the HOMO level of the molecule than MeO group, and the corresponding device demonstrated a PCE of 19.06%, much improved relative to that of PEDOT:PSS based one with a PCE of only 13.9%. To increase the conjugated degree of the core, Ma et al [94] connected the two fluorene units with a double bond instead of flexible alkyl chains, hereby obtaining a high hole mobility. Meanwhile, to maintain the advantages of spiro-like 3D structure, such as efficient ability of hole extraction and bimolecular recombination suppression, the author used four peripheral TPA units to demonstrate their flexiblecore-with-tunable-conformation (FCTC) molecular designing strategy with the purpose of balanced hole mobility and charge recombination.…”

Multiple methoxy-substituted hole transporter for inverted perovskite solar cells

“…Therefore, many small-molecule HTMs have been reported to address the issues of above-mentioned polymers [16][17][18][19]. Among them, carbazole-containing HTMs have attracted lots of attention for their good stability and strong hole-transporting ability.…”