Defect Control Strategy by Bifunctional Thioacetamide at Low Temperature for Highly Efficient Planar Perovskite Solar Cells

Alkali Metal Chloride-Doped Water-Based TiO2 for Efficient and Stable Planar Perovskite Photovoltaics Exceeding 23% Efficiency

TiO₂ is one of the most broadly employed electron transport materials in n-i-p structure perovskite solar cells (PSCs). Low-temperature non-hydrolyzed sol-gel method is developed to prepare TiO₂ in order to simplify the fabrication process and match with the planar structure PSCs. Conventional low-temperature TiO₂ film using organic solvents as dispersants makes direct doping challenging due to limited solubility. Here, a newly developed water-based TiO₂ solution is directly doped with different alkali chlorides, resulting in better conductivity, compatible energy level matching, and enhanced charge extraction in terms of electron transport layer (ETL) for PSCs. As a result, a power conversion efficiency of 23.15% is achieved based on NaCl-doped TiO₂ with competitive storage stability and light stability. The water-based TiO₂ ETL for more general doping of various solutes opens up a new avenue for environmental-friendly manufacturing superior ETL toward high-efficiency and stable perovskite photovoltaic devices.

Alkali Metal Fluoride-Modified Tin Oxide for n-i-p Planar Perovskite Solar Cells

The practical applications of perovskite solar cells (PSCs) are limited by further improvement of their stability and performance. Additive engineering and interface engineering are promising medicine to cure this stubborn disease. Herein, an alkali metal fluoride as an additive is introduced into the tin oxide (SnO₂) electron transport layer (ETL). The formation of coordination bonds of F^- ions with the oxygen vacancy of Sn⁴⁺ ions decreases the trap-state density and improves the electron mobility; the hydrogen bond interaction between the F ion and amine group (FA⁺) of perovskite inhibits the diffusion of organic cations and promotes perovskite (PVK) stability. Meanwhile, the alkali metal ions (K⁺, Rb⁺, and Cs⁺) permeated into PVK fill the organic cation vacancies and ameliorate the crystal quality of PVK films. Consequently, a SnO₂-based planar PSC exhibits a power conversion efficiency (PCE) of 20.24%, while the PSC modified by CsF achieves a PCE of 22.51%, accompanied by effective enhancement of stability and negligible hysteresis. The research results provide a typical example for low-cost and multifunctional additives in high-performance PSCs.

High-Efficiency, Low-Hysteresis Planar Perovskite Solar Cells by Inserting the NaBr Interlayer

With great research potential, the perovskite solar cells (PSCs) have been well developed in recent years, but there are still some urgent issues like efficiency and hysteresis defects that severely limit their commercialization. Interface modification is a significant measure to reduce defects and promote performance. In the article, an easy and effective strategy of modifying the electron transport layer (ETL) with NaBr is proposed to improve efficiency and reduce hysteresis. The charge carrier dynamics can be greatly optimized by diffusing NaBr on the ETL. The efficiency of the NaBr coated device can achieve 21.16%, which is extremely higher than the control one and shows low hysteresis behavior with a hysteresis index reduced from 0.135 to 0.025. The results indicate that the NaBr modification provides a novel strategy for preparing PSCs with high efficiency and low hysteresis.

Postpassivation of Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 Perovskite Films with Tris(pentafluorophenyl)borane

Passivating defects to suppress recombination is a valid tactic to improve the performance of third-generation perovskite-based solar cells. Pb⁰ is the primary defect in Pb-based perovskites. Here, tris(pentafluorophenyl)borane is inserted between the perovskite and spiro-OMeTAD layer in SnO₂-based planar perovskite solar cells. The incorporation of tris(pentafluorophenyl)borane can effectively passivate Pb⁰ defects, decreasing recombination at the surface of the perovskite film. Additionally, the modification with tris(pentafluorophenyl)borane decreases the grain boundaries quantity in the perovskite film, enhancing the transportation capability of carriers. The resulting perovskite solar cell gets a high efficiency of 21.42%. While the reference device without tris(pentafluorophenyl)borane treatment acquires an efficiency of 19.07%. More importantly, the stability tests manifest that incorporating tris(pentafluorophenyl)borane in perovskite solar cells is conducive to the stability of the device.