Novel Quasi-2D Perovskites for Stable and Efficient Perovskite Solar Cells

Compared to three-dimensional (3D) organic-inorganic hybrid perovskites, two-dimensional (2D) ones possess great possibilities to realize stable cost-effective perovskite solar cells (PSCs). However, studies indicated that PSCs with 2D perovskites exhibited poor power conversion efficiencies (PCEs). In this study, we report novel propargylamine cation (PPA⁺)-based quasi-2D perovskites. PPA⁺ employed as an organic spacer is for enhancing charge-carrier transport of quasi-2D (PPA)₂(CH₃NH₃)₂Pb₃I₁₀ thin films, consequently boosting PCEs of PSCs. To further boost PCEs of PSCs with quasi-2D (PPA)₂(CH₃NH₃)₂Pb₃I₁₀ thin films, a quasi-2D (PPA)₂(CH₃NH₃)₂Pb₃I₁₀ thin film is processed with Pb(SCN)₂ additives. Systematical studies indicate that the quasi-2D (PPA)₂(CH₃NH₃)₂Pb₃I₁₀ thin film processed with Pb(SCN)₂ additives exhibits superior film morphology and crystallinity, larger crystals, reduced nonradiative charge-carrier recombination, and enhanced and balanced charge-carrier mobilities compared to the pristine quasi-2D (PPA)₂(CH₃NH₃)₂Pb₃I₁₀ thin film. As a result, PSCs with the quasi-2D (PPA)₂(CH₃NH₃)₂Pb₃I₁₀ thin film processed with Pb(SCN)₂ additives exhibit a PCE of 15.20%, which is an over 25% enhancement compared to those (12.16%) with a pristine quasi-2D (PPA)₂(CH₃NH₃)₂Pb₃I₁₀ thin film. In addition, PSCs with the quasi-2D (PPA)₂(CH₃NH₃)₂Pb₃I₁₀ thin film processed with Pb(SCN)₂ additives possess dramatically suppressed photocurrent hysteresis and significantly boosted stability. All these results indicate that we have developed a facile way to synthesize novel 2D perovskite thin films for realizing stable and efficient PSCs with dramatically suppressed photocurrent hysteresis.