Regioisomeric Effects on Enhancing p-Type Characteristics of Self-Assembled Molecules in Inverted Perovskite Solar...

Area of Science:

• Materials Science
• Photovoltaics
• Organic Chemistry

Background:

• Self-assembled molecules (SAMs) are crucial for advancing inverted perovskite solar cells (PSCs).
• Key challenges include achieving uniform surface potential and minimizing interfacial energy losses in PSCs.
• Functional modulators are needed to optimize the performance of widely used phosphonic acid derivatives like Me-4PACz.

Purpose of the Study:

• To investigate the impact of regioisomers of dibromodibenzothiophene-5,5-dioxide as functional modulators for Me-4PACz in PSCs.
• To compare the effects of meta-substituted (3,7-Br) and para-substituted (2,8-Br) regioisomers on interfacial properties and device performance.
• To elucidate the structure-property relationships governing the enhanced performance observed with the 2,8-Br isomer.

Main Methods:

• Synthesis and characterization of 3,7-dibromodibenzothiophene-5,5-dioxide (3,7-Br) and 2,8-dibromodibenzothiophene-5,5-dioxide (2,8-Br) regioisomers.
• Incorporation of these regioisomers as functional modulators with Me-4PACz in inverted perovskite solar cells.
• Detailed analysis of interfacial properties, including π-π interactions, energy level alignment, and charge carrier dynamics.
• Performance evaluation of PSCs based on power conversion efficiency (PCE), light-soaking stability, and thermal stability.

Main Results:

• The para-substituted 2,8-Br regioisomer exhibited stronger π-π interactions with Me-4PACz compared to the meta-substituted 3,7-Br.
• 2,8-Br facilitated enhanced p-type characteristics and more favorable energy level alignment, improving hole extraction.
• Interfacial defect passivation and suppression of non-radiative recombination were more effective with 2,8-Br due to interactions with the perovskite layer.
• PSCs treated with Me-4PACz and 2,8-Br achieved a power conversion efficiency (PCE) of 25.40%, an increase from 23.40% in the control device.
• The 2,8-Br treated PSCs showed improved light-soaking and thermal stability (85°C) compared to control devices.

Conclusions:

• Regioisomers of dibromodibenzothiophene-5,5-dioxide serve as effective functional modulators for phosphonic acid derivatives in PSCs.
• The 2,8-Br isomer's unique electronic and structural properties lead to superior interfacial engineering, enhancing PCE and stability.
• This study highlights the potential of tailored molecular design for optimizing perovskite solar cell performance and durability.