A Polymerization‐Assisted Grain Growth Strategy for Efficient and Stable Perovskite Solar Cells

Abstract

Intrinsically, detrimental defects accumulating at the surface and grain boundaries limit both the performance and stability of perovskite solar cells. Small molecules and bulkier polymers with functional groups are utilized to passivate these ionic defects but usually suffer from volatility and precipitation issues, respectively. Here, starting from the addition of small monomers in the PbI2 precursor, a polymerization‐assisted grain growth strategy is introduced in the sequential deposition method. With a polymerization process triggered during the PbI2 film annealing, the bulkier polymers formed will be adhered to the grain boundaries, retaining the previously established interactions with PbI2. After perovskite formation, the polymers anchored on the boundaries can effectively passivate undercoordinated lead ions and reduce the defect density. As a result, a champion power conversion efficiency (PCE) of 23.0% is obtained, together with a prolonged lifetime where 85.7% and 91.8% of the initial PCE remain after 504 h continuous illumination and 2208 h shelf storage, respectively.

Roles of MACl in Sequentially Deposited Bromine‐Free Perovskite Absorbers for Efficient Solar Cells

“…Simultaneously mounting planar solar cells with high performance have been reported to utilize FA‐based perovskites as light absorbers using sequential deposition that is highly reproducible with thick vertical columnar grains. [ 23–27 ] Different from the antisolvent deposition in which intermediates form, [ 28 ] perovskites with the sequential deposition evolve from the intercalation between lead halides and organic amine salts. [ 29,30 ] As a result, strategies to stabilize FAPbI 3 are different.…”

Minimizing Voltage Losses in Perovskite Solar Cells

“…For instance, Lewis base monomers such as dimethyl itaconate and methyl methacrylate can self‐polymerize via the cleaving of the CC bonds during the annealing process, whereas their abundant CO groups enable the interaction with the positively charged defects at the GBs, leading to the reduced device voltage loss by 30–50 mV. [ 75,76 ] In a similar manner, the incorporation of hydrolytic siloxane in the precursor solution could induce the in situ formation of oligomeric silica matrixes to wrap the perovskite grains via hydrolysis and condensation processes. The presence of electrophile Si–OH or nucleophile Si–OCH 2 CH 3 groups effectively suppressed nonradiative recombination at the GBs and thus the oligomeric silica‐wrapped PSCs yielded a V oc enhancement by 40–50 mV.…”

Organic Dye Passivation for High‐Performance All‐Inorganic CsPbI1.5Br1.5 Perovskite Solar Cells with Efficiency over 14%

“…[ 31 ] These defects act primarily as nonradiative recombination centers, contributing to significant open‐circuit voltage loss ( V oc,loss ). [ 32,33 ] It has been demonstrated that among all defect types, under‐coordinated lead ions (Pb 2+ ) show relatively low formation energy and is one of the main origins of defects. [ 34,35 ] To reduce V oc,loss , defect passivation has been widely used by adding a variety of passivators that can interact with under‐coordinated metal ions.…”