Dopant‐Free Squaraine‐Based Polymeric Hole‐Transporting Materials with Comprehensive Passivation Effects for Efficient All‐Inorganic Perovskite Solar Cells

Abstract

Development of high‐performance dopant‐free hole‐transporting materials (HTMs) with comprehensive passivation effects is highly desirable for all‐inorganic perovskite solar cells (PVSCs). Squaraines (SQs) could be a candidate for dopant‐free HTMs as they are natural passivators for perovskites. One major limitation of SQs is their relatively low hole mobility. Herein we demonstrate that polymerizing SQs into pseudo two dimensional (2D) p–π conjugated polymers could overcome this problem. By rationally using N,N‐diarylanilinosquaraines as the comonomers, the resulting polysquaraine HTMs not only exhibit suitable energy levels and efficient passivation effects, but also achieve very high hole mobility close to 0.01 cm−2 V−1 s−1. Thus as dopant‐free HTMs for α‐CsPbI2Br‐based all‐inorganic PVSCs, the best PCE reached is 15.5 %, outperforming those of the doped‐Spiro‐OMeTAD (14.4 %) based control devices and among the best for all‐inorganic PVSCs.

Inorganic Halide Perovskite Solar Cells: Progress and Challenges

“…The hole mobility of doped Spiro‐OMeTAD was estimated to be 3.32 × 10 −3 cm 2 V −1 s −1 . [ 46 ] PEDOT:PSS is mainly applied into the p–i–n structure, with a high hole mobility of >10 −2 cm 2 V −1 s −1 . PTAA, which has conjugated chains and exhibits a rather high stability, is the main polymer HTM for both p–i–n‐ and n–i–p‐type PSCs with high efficiencies.…”

Effective Surface Treatment for High-Performance Inverted CsPbI2Br Perovskite Solar Cells with Efficiency of 15.92%

“…To date, a high efficiency of 16.79% has been realized with a regular structure (n-i-p) CsPbI 2 Br perovskite solar cells (PSCs) [9]. However, as universally used HTL materials, the 2,2′,7,7′-tetrakis (N,N-dipmethoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) and poly[bis(4-phenyl) (2,4,6-trimethylphenyl)amine] (PTAA) always need additional dopant of hygroscopic bis(trifluoromethanesulfonyl)imide lithium salt (Li-TFSI) and low-boil-point tert-butylpyridine (t-BP) to increase holes mobility [10][11][12][13][14]. The undesired dopants, which would open channels for moisture erosions and suffer from the uneven distribution under evaluated temperature, gift devices poor moisture/thermal stability and seriously limit their long-term used under real working condition [15,16].…”

Efficient Inverted Perovskite Solar Cells with Low Voltage Loss Achieved by a Pyridine‐Based Dopant‐Free Polymer Semiconductor

“…[72] We thus examined the longterm photostability of unencapsulated devices by monitoring the evolution of PCEs with continuous one sun illumination in N 2 atmosphere at room temperature for 500 h. As shown in Figure 6, PPY2-based devices can encouragingly maintain over 97 %ofinitial PCE after 500 h, with almost no decline in all device parameters.I nc ontrast, only 75 %o ft he initial value was retained for PTAA-based devices under the same test conditions.T he SEM and XRD measurements (Figures S16,17) suggest ac lear degradation occurring for perovskites atop PTAA compared to PPY2 after 200 hl ight soaking.T his thus could be attributed to the effective passivation effects of PPY2.Inaddition, removal of harmful dopants should also play arole. [73,74]…”