Breaking down the confinement effect on perovskite growth to fabricate efficient, carbon electrode-based mesoscopic perovskite solar cells via low-temperature and all-air procedures†

Abstract

Mesoporous skeleton brings confinement effect during the crystallization of the perovskite active layer, thus restricting the power conversion efficiency (PCE) of carbon-electrode (CE)-based, hole-conductor-free, mesoscopic perovskite solar cells (meso-CPSCs), especially of those prepared via low-temperature procedures. Here, the confinement is broken down by newly released micron-sized carbon-black spheres (CBSs). These CBSs help enlarge the mesopores from <10 to ∼70 nm in the CE layer and break down the confinement effect over perovskite growth. With carbon-black mass increasing from 0.0625 to 0.5 g, the average crystallite size of the PVSK increases from 30.9 to 58.2 nm, in addition to the improved contact at the buried interface of the PVSK. Accordingly, charge extraction is accelerated, recombination is retarded, and the PCE of low-temperature (150 °C) and all-air processed meso-CPSCs increases from 4.89 (±1.22)% to 11.33 (±0.28)%, which is further elevated to 16.28% through usage of thicker CEs. The strategy thus improves the PCE by more than 30% compared with the value reported in 2020, which competes with that of high-temperature (450 °C) produced meso-CPSCs when using similar (5-AVA)_x(MA)_1−xPbI₃ as a photoactive layer. Quasi-maximum power point tracking was performed; a T80 of ∼690 h (the time required for PCE to reach 80% of its original value) was obtained for the first time for such low-temperature processed meso-CPSCs. This research paves the way to fabricate efficient meso-CPSCs using low-temperature and all-air procedures, which are expected to reduce production costs.