A multifunctional p-type additive for enhanced efficiency in perovskite solar cells†

Abstract

Organic/inorganic hybrid perovskite solar cells (PSCs) still face significant challenges related to carrier recombination caused by numerous defects and an unfavorable energy level alignment. In this study, we introduce a multifunctional p-type organic molecule, dioctylbenzothieno[2,3-b]benzothiophene (C8BTBT), as an additive, aimed at enhancing the device performance. Our investigation reveals that the incorporation of C8BTBT effectively enhances perovskite crystalline quality, diminishes nonradiative recombination, improves perovskite electrical properties and optimizes energy level alignment. These improvements collectively contribute to the advancement of PSC devices. Impressively, a remarkable power conversion efficiency (PCE) exceeding 22% is achieved, accompanied by an open-circuit photovoltage of 1.12 V, a short-circuit photocurrent density of 24.58 mA cm⁻², and a fill factor of 0.80. Furthermore, we evaluate the long-term stability of unencapsulated devices over 1000 hours under ambient conditions (with a temperature of 20 °C and humidity of 30%). The PSCs incorporating C8BTBT demonstrate a normalized PCE retention of 93% compared to their initial performance, while the control devices retain 82% of their initial efficiency.