Interfacial Modification and Defect Passivation by the Cross-Linking Interlayer for Efficient and Stable CuSCN-Based Perovskite Solar Cells

Abstract

The study of the inorganic hole-transport layer (HTL) in perovskite solar cells (PSCs) is gathering attention because of the drawback of the conventional PSC design, where the organic HTL with salt dopants majorly participates in the degradation mechanisms. On the other hand, inorganic HTL secures better stability, while it offers difficulties in the deposition and interfacial control to realize high-performing devices. In this study, we demonstrate polydimethylsiloxane (PDMS) as an ideal polymeric interlayer which prevents interfacial degradation and improves both photovoltaic performance and stability of CuSCN-based PSC by its cross-linking behavior. Surprisingly, the PDMS polymers are identified to form chemical bonds with perovskite and CuSCN, as shown by Raman spectroscopy. This novel cross-linking interlayer of PDMS enhances the hole-transporting property at the interface and passivates the interfacial defects, realizing the PSC with high power-conversion efficiency over 19%. Furthermore, the utilization of the PDMS interlayer greatly improves the stability of solar cells against both humidity and heat by mitigating the interfacial defects and interdiffusion. The PDMS-interlayered PSCs retained over 90% of the initial efficiencies, both after 1000 h under ambient conditions (unencapsulated) and after 500 h under 85 °C/85% relative humidity (encapsulated).

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

“…In addition, the devices with such interfacial modification also showed better long-term stability and less J-V hysteresis in comparison to that of pristine devices. Kim et al [89] introduced polydimethylsiloxane (PDMS) as a polymeric interlayer in CuSCN-based PSCs to prevent interfacial degradation and improve both conversion efficiency and stability. They identified that PDMS could combine with perovskite and CuSCN in chemical bonds, which could enhance the hole transporting at the interface and passivate the interfacial defects.…”

CuCrO2 Nanoparticles Incorporated into PTAA as a Hole Transport Layer for 85 °C and Light Stabilities in Perovskite Solar Cells

“…Time-resolved PL spectra, as seen in Figure 2 b, exhibited faster early-stage decay with CuCrO 2 /PTAA compared to PTAA, 14 vs. 28 ns, respectively [ 62 , 63 , 64 ]. To characterize the hole-extracting mobility more quantitatively, dark current-voltage (J-V) characteristics under DC bias were examined for the SCLC region with the ITO/HTL/Au structure ( Figure 2 c) [ 65 , 66 ]. The hole mobilities were 2.6 × 10 −3 and 1.2 × 10 −3 cm 2 V −1 s −1 for CuCrO 2 /PTAA and bare PTAA, respectively, further supporting the role of high-mobility CuCrO 2 nanoparticles which enable faster hole extraction from the perovskite along the HTL.…”

Defects and Their Passivation in Hybrid Halide Perovskites toward Solar Cell Applications

“…[141] The introduction of a polymer interlayer, namely polydimethylsiloxane (PDMS) in between the perovskite and HTL, has been found obliging, due to the cross-linking behaviour of the polymer in reducing the interfacial charge recombination. [142] Similarly, the passivation layer can be situated in between the perovskite film and the ETL. Fullerene has been considered to be a very useful passivation agent in this context.…”

“…[ 141 ] The introduction of a polymer interlayer, namely polydimethylsiloxane (PDMS) in between the perovskite and HTL, has been found obliging, due to the cross‐linking behaviour of the polymer in reducing the interfacial charge recombination. [ 142 ]…”