Efficient and Moisture‐Stable Inverted Perovskite Solar Cells via n‐Type Small‐Molecule‐Assisted Surface Treatment

Abstract

Defect states at the surface and grain boundaries of perovskite films have been known to be major determinants impairing the optoelectrical properties of perovskite films and the stability of perovskite solar cells (PeSCs). Herein, an n-type conjugated small-molecule additive based on fused-unit dithienothiophen[3,2-b]-pyrrolobenzothiadiazole-core (JY16) is developed for efficient and stable PeSCs, where JY16 possesses the same backbone as the widely used Y6 but with long-linear n-hexadecyl side chains rather than branched side chains. Upon introducing JY16 into the perovskite films, the electron-donating functional groups of JY16 passivate defect states in perovskite films and increase the grain size of perovskite films through Lewis acid-base interactions. Compared to Y6, JY16 exhibits superior charge mobility owing to its molecular packing ability and prevents decomposition of perovskite films under moisture conditions owing to their hydrophobic characteristics, improving the charge extraction ability and moisture stability of PeSCs. Consequently, the PeSC with JY16 shows a high power conversion efficiency of 21.35%, which is higher than those of the PeSC with Y6 (20.12%) and without any additive (18.12%), and outstanding moisture stability under 25% relative humidity, without encapsulation. The proposed organic semiconducting additive will prove to be crucial for achieving highly efficient and moisture stable PeSCs.

Modulation of intermolecular interactions in hole transporting materials for improvement of perovskite solar cell efficiency: a strategy of trifluoromethoxy isomerization

“…27 The alignment of energy levels for HTMs with the perovskite is crucial for enhancing the photovoltaic efficiency. 28 A better alignment of energy levels not only improves hole extraction and transport but also minimizes energy losses. 29 As shown in Table 1, employing the B3P86/6-311G(d,p) functional and basis set, the HOMO energy levels for JY4, JY5, and JY6 are calculated to be −5.14, −5.15, and −5.10 eV, respectively.…”

In situ dipole formation to achieve high open-circuit voltage in inverted perovskite solar cells via fluorinated pseudohalide engineering

“…15 Moreover, Li et al and Hong et al introduce N-type small molecules to optimize the perovskite/ETL interface, increase the charge transfer channel, and adjust the energy-level distribution. 16,17 Unfortunately, the small molecules at the perovskite/ETL interface can be easily destroyed and spread upward or downward, which negatively affects the photovoltaic performance and working stability of p–i–n PSCs. Therefore, it is urgent to develop an in situ passivation technology to regulate the energy levels near the top surface in p–i–n PSCs.…”

First-principles calculation analysis and photovoltaic properties of Cu compound-added perovskite solar cells

“…In recent years, a wide range of approaches have been continued to improve the conversion efficiency and durability of perovskite solar cells, including the introduction of phase stabilizers into FA-based perovskite crystals, 1) the use of dopant-free hole transport polymer materials, 2) and surface treatment with n-type small molecule complexes. 3) In general, compositions of halide perovskite crystals are ABX 3 , consisting of A: organic cations, B: metal cations, and C: halogen anions. Perovskite solar cells with high conversion efficiencies often contain toxic lead, and the use of toxic lead is a problem for commercialization in terms of its impact on human health and the environment.…”