High-efficiency and durable inverted perovskite solar cells with thermally-induced phase-change electron extraction layer

Abstract

Reducing carrier recombination and facilitating charge extraction at the interface is of great significance to improve the device performance of perovskite solar cells (PSCs) towards commercial use. However, there has been little work done concerning transportation and recombination mechanism at the interface of the metal electrode and the electron transport layer in inverted PSCs. Herein, a new strategy of interface modification is reported that leverages the unique metal-to-insulator transition (MIT) characteristics of vanadium dioxide which is inserted as the electron extraction layer (EEL) in p-i-n planar PSCs. Benefiting from the suitable intermediate energy level of VO2, the optimized device shows a power conversion efficiency (PCE) up to 22.11% with negligible hysteresis, as compared to the 20.96% benchmark at room temperature. Interestingly, the PCE of VO2-based PSC increases to over 23% at 85 °C, which can be attributed to the dramatic change in the electrical properties and better electron extraction caused by the MIT of VO2 beyond its critical phase-change temperature. In addition, the encapsulated VO2-PSC shows superior thermal stability for 1000 h at 85 °C under 1 Sun illumination, maintaining over 90% of initial PCE. This work initiates the state-of-art concept of inserting thermally-induced phase-transition material as an EEL to achieve efficient and durable perovskite photovoltaics.