Spontaneous interface engineering for dopant-free poly(3-hexylthiophene) perovskite solar cells with efficiency over 24%

Abstract

Halide perovskite solar cells (PSCs) have recently shown a leap forward in performance by reducing the recombination loss at the interface between the perovskite and hole-transporting layers through surface treatment. However, additional surface treatment processes such as spin-coating or annealing are undesirable for commercialization in terms of the production cost. In addition, commonly used organic hole-transporting materials (HTMs) such as 2,2′,7,7′-tetrakis[N,N-di(4methoxylphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) and poly(triarylamine) (PTAA) are used with hygroscopic additives, which deteriorate the long-term stability and hinder the commercialization of PSCs. Herein, we report an efficient strategy for interface engineering by directly incorporating gallium(III) acetylacetonate (Ga(acac)₃) into HTMs without subsequent processes and hygroscopic dopants. The incorporated Ga(acac)₃ spontaneously interacts with the surface of the perovskite layer, yielding a reduction of the interfacial recombination loss for various organic HTMs. In particular, by applying Ga(acac)₃ in poly(3-hexylthiophene) (P3HT), the PSCs showed a significant improvement in the power conversion efficiency (PCE) from 17.7% for the control device to 21.8%. The Ga(acac)₃-devices also showed superior moisture stability for 2000 hours under 85% relative humidity at room temperature without any encapsulation, maintaining a complete initial performance. We also demonstrated that the incorporated Ga(acac)₃ successfully works on the best-known PSCs with the aligned P3HT, showing an enhanced PCE of 24.6%. We believe that this work presents a route for the high performance and commercialization of PSCs.