Correlating the perovskite/polymer multi-mode reactions with deep-level traps in perovskite solar cells

Abstract

•A PEI/perovskite multi-mode interaction including a newfound in-situ protonation •Correlation of in-situ reaction with the deep-level trap of minority carrier •Broad applicability for passivating different perovskites •p-i-n devices with enhanced operational stability and a high PCE of 24.3% The present p-i-n perovskite solar cells are less efficient than their n-i-p counterparts, fundamentally limited by deep-level traps of minority carriers at surfaces. Here, we explore perovskite/polymer multi-mode interactions by comparing the amine group’s various configurations and protonation states in the polyethylenimine (PEI) family. We correlate these interactions with specific deep-trap states by combining deep-level transient spectroscopy (DLTS) and density functional theory (DFT). We identify an in-situ protonation process that significantly reduces deep-level traps of minority carriers. The conventional ex-situ protonated and non-protonated groups do not exhibit this effect. For 1.55-eV p-i-n device, we achieve a high power conversion efficiency (PCE) of 24.3%. For 1.65-eV p-i-n devices directly applicable for tandem on silicon bottom cells, the PCE is improved from 19.4% to 22.3%. The cells exhibit no degradation in accelerated aging testing at 85°C for >1,000 h and maximum-power-point (MPP) tracking for >1,000 h. The present p-i-n perovskite solar cells are less efficient than their n-i-p counterparts, fundamentally limited by deep-level traps of minority carriers at surfaces. Here, we explore perovskite/polymer multi-mode interactions by comparing the amine group’s various configurations and protonation states in the polyethylenimine (PEI) family. We correlate these interactions with specific deep-trap states by combining deep-level transient spectroscopy (DLTS) and density functional theory (DFT). We identify an in-situ protonation process that significantly reduces deep-level traps of minority carriers. The conventional ex-situ protonated and non-protonated groups do not exhibit this effect. For 1.55-eV p-i-n device, we achieve a high power conversion efficiency (PCE) of 24.3%. For 1.65-eV p-i-n devices directly applicable for tandem on silicon bottom cells, the PCE is improved from 19.4% to 22.3%. The cells exhibit no degradation in accelerated aging testing at 85°C for >1,000 h and maximum-power-point (MPP) tracking for >1,000 h.