EN02.12.02 : Impact of Ultrathin Charge Selective Layers for Inverted Perovskite Solar Cells

5:00 PM–7:00 PM Apr 5, 2018

PCC North, 300 Level, Exhibit Hall C-E

Dianyi Liu1 Qiong Wang1 Mark Elinski1 Christopher Traverse1 Pei Chen1 Chenchen Yang1 Margaret Young1 Thomas Hamann1 Richard Lunt1

1, Michigan State University, East Lansing, Michigan, United States

A range of electron transfer layers (ETL) and hole transfer layers (HTL) have been actively investigated for perovskite solar cells (PSCs). In this work, we demonstrate the ability to utilize < 2 nm of such layers on both sides of perovskites devices. On the n-side, we show that ultrathin (1 nm) layer of vapor-deposited C60 can switch on the perovskite device by primarily enabling efficient electron extraction and eliminating space charge at the interface which are investigated by utilizing time-resolved fluorescence microscopy and impedance spectroscopy. The study is also suggests that the ultrathin C60 layer alone is sufficient to eliminate hysteresis by enabling efficient electron extraction. In contrast, the device shows poor efficiency (PCE < 1%) and large hysteresis in the absence of the 1 nm of C60. On the p-side, we systematically investigate the role of PEDOT:PSS in inverted structures. PEDOT, one of the most popular HTL layers in inverted PSCs, typically suffer from lower device performance, lower photocurrent, and inferior open-circuit voltages. In this work, we report an ultrathin PEDOT layer as the HTL for efficient inverted structure PSCs. The ultrathin layer of PEDOT can significantly change the wetting property of transparent electrode surface, leading to changes in the grain size, crystallization, and injection properties of the upper perovskite film. We will systematically discuss the role of each transport layer and underlying mechanisms for their key function. Surprisingly by utilizing both ultrathin fullerene layer and ultra-thin PEDOT layer, we show that PCEs of over 18% are possible. These demonstrations ultimately aid in the understanding of the true role of these layers in perovskite solar cells, and highlights that very little is needed to make efficient halide perovskites photovoltaics beyond just the perovskite itself and ohmic electrodes. This represents the simplest high efficiency halide perovskite demonstrated to date. This will ultimately enable simpler manufacturing and lower fabrication costs while changing the way researchers think about perovskite semiconductor heterojunctions and perovskite photovoltaic design.