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 cells^1-5. 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 stability^6,7. 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.