Defects Passivation With Dithienobenzodithiophene‐based π‐conjugated Polymer for Enhanced Performance of Perovskite Solar Cells

Abstract

A dithienobenzodithiophene‐based π‐conjugated polymer consisting of fluorinated benzotriazole and benzothiadiazole is successfully applied through anti‐solvent method to passivate the defects of perovskite crystals. The fluorinated polymer interacts with under coordinated Pb2+ ions in the perovskite crystals to form Pb‐F bond which effectively passivates the defects. The trap density is reduced and the charge carrier transfer between the perovskite film and Spiro‐OMeTAD is also improved after passivation with the polymer. As a result, a power conversion efficiency (PCE) of 18.03% is achieved in the champion cell. After storing in an ambient environment with 60% relative humidity for 1000 h, the device still retains 90% of the original PCE. These results demonstrate that dithienobenzodithiophene‐based π‐conjugated polymers are promising materials for passivation of perovskite films to further improve the performance and stability of perovskite solar cells.

Defect Passivation in Perovskite Solar Cells by Cyano‐Based π‐Conjugated Molecules for Improved Performance and Stability

“…[ 28 ] Kyaw et al have observed the Pb 4f binding energy shifted to a lower value when introducing PDTBDT‐FBT solutions as antisolvent. [ 14 ] In our case, the shift of binding energy might come from the coordination bond formed between the Pb 2+ and the cyano functional unit with a high electron density.…”

“…Previous reports demonstrate that the passivants which enable Lewis acid–base interactions can aid in nucleation and growth of the crystallization process, leading to a better orientation of perovskite grains. [ 7,14,27 ]…”

“…Numerous strategies have already been proposed for the passivation of defects in perovskites, such as the use of ionic liquids, [ 11 ] alkali metal cations, [ 12 ] polymers, [ 13,14 ] self‐assembled molecules, [ 15 ] and fullerene derivatives. [ 8,16 ] Certain organic molecules with carboxyl, amino, carbonyl, and pyridine functional groups have been explored as well due to their inherent advantages such as ease of synthesis and purification, well‐defined structure, good tolerance to moisture and solution processability.…”

Interface Dipole Induced Field‐Effect Passivation for Achieving 21.7% Efficiency and Stable Perovskite Solar Cells

“…Figure S8 (Supporting Information) shows the space charge limit current (SCLC) curves (including hole‐only and electron‐only setups) of the PSCs with‐ and without‐MoO x interlayers. The trap state density ( N t ) within the perovskite films can be calculated via [ 39 ] …”

“…Recently, we have observed this phenomenon in Si solar cells. [35,39] This charge transfer creates interfacial polarization, which induces the FEP by efficient separating photogenerated carriers and reducing the probability of Shockley-Read-Hall (SRH) recombination at the heterointerface. [40] Thus, we argue that the FEP caused by the MoO x interlayer may domain the photovoltaic improvement.…”