Non-wetting surface-driven high-aspect-ratio crystalline grain growth for efficient hybrid perovskite solar cells

Abstract

Large-aspect-ratio grains are needed in polycrystalline thin-film solar cells for reduced charge recombination at grain boundaries; however, the grain size in organolead trihalide perovskite (OTP) films is generally limited by the film thickness. Here we report the growth of OTP grains with high average aspect ratio of 2.3–7.9 on a wide range of non-wetting hole transport layers (HTLs), which increase nucleus spacing by suppressing heterogeneous nucleation and facilitate grain boundary migration in grain growth by imposing less drag force. The reduced grain boundary area and improved crystallinity dramatically reduce the charge recombination in OTP thin films to the level in OTP single crystals. Combining the high work function of several HTLs, a high stabilized device efficiency of 18.3% in low-temperature-processed planar-heterojunction OTP devices under 1 sun illumination is achieved. This simple method in enhancing OTP morphology paves the way for its application in other optoelectronic devices for enhanced performance.

Efficient and Air‐Stable Mixed‐Cation Lead Mixed‐Halide Perovskite Solar Cells with n‐Doped Organic Electron Extraction Layers

“…[38] A recent study comparing different p-type organic hole conductors used in inverted p-i-n perovskite solar cells suggests that relatively nonwetting/hydrophobic substrates facilitate larger crystalline domain growth of the perovskite layers. [39] We observe similar results here, where increasing the hydrophilic nature of the C 60 film by doping has led to reduced XRD peak intensity and broadening of the peak width, which we interpret to indicate lower crystallinity in the perovskite films. [38,40] However, as we previously noted, the neat C 60 film appears to be too hydrophobic, resulting in void formation at the perovskite C 60 interface.…”

Recent Progress on the Long‐Term Stability of Perovskite Solar Cells

“…Doping with nanoparticles or conductive oxides, for example polyethylene oxide (PEO),138 molybdenum oxide (MoO 3 ),139 graphene oxide (GO)140 is a commendable option for tuning the properties of PEDOT:PSS. More importantly, employing polytriarylamine (PTAA)13, 141 and poly(3‐hexylthiophene‐2,5‐diyl) (P3HT)142 to substitute PEDOT:PSS has been tested to dramatically improve the device stability. Bi et al fabricated CH 3 NH 3 PbI 3 film with large crystalline grains on PTAA HTL which dramatically reduced charge trap density and enhanced the PCE to ≈18.1% for planar PVSCs with its higher hole mobility 65.…”

Recent Advance in Solution‐Processed Organic Interlayers for High‐Performance Planar Perovskite Solar Cells

“…Huang and co‐workers grew CH 3 NH 3 PbI 3 film on a wide range of wetting and nonwetting HTMs, including polyvinyl alcohol (Figure 5), PEDOT:PSS, cross‐linked N4,N4′‐bis(4‐(6‐((3‐ethyloxetan‐3‐yl)methoxy) hexyl)phenyl)‐N4,N4′‐diphenylbiphenyl‐4,4′‐diamine (C‐OTPD), PTAA, and (N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)) (PCDTBT, Figure 5). 105 With the increased nucleus spacing and the facilitated grain boundary migration in grain growth, the charge recombination in perovskite film on nonwetting HTMs was reduced. As a result, high stabilized device efficiencies of 18.3% and 17.8% were obtained, respectively, based on tetrafluoro‐tetracyanoquinodimethane (F4‐TCNQ) doped PTAA and C‐OTPD HTMs.…”