Electronic-resonance enhanced molecule for perovskite solar cells

Abstract

Self-assembled monolayers (SAMs), which anchor to transparent conductive oxide substrates and form an interfacial molecular dipole to extract carriers from a perovskite layer, have promoted a stepwise improvement in the efficiency of perovskite solar cells1–5. However, the limited intrinsic bonding strength due to the constrained electron density on coordination sites allows the SAMs to desorb and compromises charge extraction under operational stressors, posing a notable challenge to their long-term stability6,7. Here, to address this, we designed a SAM with donor–acceptor–donor resonant molecular structure, in which the electronic resonance increases the negative charge density at the acceptor-anchoring group, substantially strengthening the phosphonic acid–indium tin oxide anchoring bond and preventing the desorption of the SAM during operation. Devices made with a donor–acceptor–donor resonant SAM have notable operational stability with negligible decay under maximum-power-point tracking at 85 ± 5 °C for 1,080 h. They maintained over 93% of the initial power conversion efficiency after 1,080 h of illumination by a metal halide lamp (100 mW cm−2, 4.4% ultraviolet inside) at 85 ± 5 °C and also retained over 97% after 720 repeated thermal cycles between −40 °C and 85 °C. Concurrently, the resonance-induced charge delocalization facilitates efficient carrier transport, realizing certified power conversion efficiencies of 27.69% on 0.063 cm2 devices and 23.63% with an aperture area of 15.64 cm2. A certified efficiency of 26.64% was also realized on flexible substrates (0.063 cm2), demonstrating the universality of this approach for different types of substrates. In a self-assembled monolayer molecule with a donor–acceptor–donor structure, the electronic resonance increased the negative charge density at the acceptor-anchoring group, improving the certified efficiencies of rigid and flexible perovskite solar cells.