Constructing D-π-A Type Polymers as Dopant-Free Hole Transport Materials for High-Performance CsPbI₂Br Perovskite Solar Cells

Abstract

Hole-transporting materials (HTMs) play a major role in efficient and stable perovskite solar cells (PSCs), especially for CsPbI2Br inorganic PSC. Among them, dopant-free conjugated polymers attract more attention because of the advantages of high hole mobility and high stability. However, the relationship between the polymer structure and the photovoltaic performance is rarely investigated. In this work, we choose three similar D-π-A-type polymers, where the D unit and π-bridge are fixed into benzodithiophene and thiophene, respectively. By changing the A units from classic benzodithiophene-4,8-dione and benzotriazole to quinoxaline, three polymers PBDB-T, J52, and PE61 are utilized as dopant-free HTMs for CsPbI2Br PSCs. The energy levels, hole mobility, and molecular stacking of the three HTMs, as well as charge transfer between CsPbI2Br/HTMs, are fully investigated. Finally, the device based on PE61 HTM obtains the champion power conversion efficiency of 16.72%, obviously higher than PBDB-T (15.13%) and J52 (15.52%). In addition, the device based on PE61 HTM displays the best long-term stability. Those results demonstrate that quinoxaline is also an effective A unit to construct D-π-A-type polymers as HTMs and improve the photovoltaic performance of PSCs.

Tailoring the Perovskite Structure to Acquire an Inorganic La2NiCrO6 Double Perovskite as an Efficient Energy Storage Application by Varying Molar Concentrations of Citric Acid

“…A cubic system value of “ t ” is usually between 0.9 and 1. The value of “ t ” less than 0.89 leads to an orthorhombic perovskite structure. − For La 2 NiCrO 6 , the “ t ” value is approximately equal to 0.85; from this, it is concluded that it has an orthorhombic structure, which agrees with the JCPDS number 87-0015 data.…”

A review on conventional perovskite solar cells with organic dopant-free hole-transport materials: roles of chemical structures and interfacial materials in efficient devices

“…Concerning D-A copolymers, the rigid and planar conjugation makes BDT one of the most investigated D unit. 156,174,175 Huang and Xue reported two BDT-based polymers PBTI and PFBTI in which bithiophene imide (BTI) was introduced as A unit. 149 Impressively, the devices with these two polymers exhibited PCEs above 22% (22.6% for PBTI and 23.1% for PFBTI), outperforming the device with doped spiro-OMeTAD (21.4%).…”

All‐Inorganic Perovskite Solar Cells: Modification Strategies and Challenges

“…Consequently, considerable efforts have been dedicated to identifying high-quality HTM candidates to replace spiro-OMeTAD. [95,[97][98][99][100] 7b). [98] It has been observed that PCPDTBT can not only enhance hole extraction and transportation efficiency but also, due to its hydrophobic properties, contribute to the improved humidity durability of all-inorganic perovskites.…”