Reduced-dimensional perovskite photovoltaics with homogeneous energy landscape

Tingwei He,Run Long,Mingjian Yuan,Huanhua Wang,Minghuan Cui,Yuanzhi Jiang,Lu Qiao,Chaochao Qin,Saisai Li,Hongyu Xu,Jien Yang

doi:10.1038/s41467-020-15451-1

Abstract

Reduced-dimensional (quasi-2D) perovskite materials are widely applied for perovskite photovoltaics due to their remarkable environmental stability. However, their device performance still lags far behind traditional three dimensional perovskites, particularly high open circuit voltage (Voc) loss. Here, inhomogeneous energy landscape is pointed out to be the sole reason, which introduces extra energy loss, creates band tail states and inhibits minority carrier transport. We thus propose to form homogeneous energy landscape to overcome the problem. A synergistic approach is conceived, by taking advantage of material structure and crystallization kinetic engineering. Accordingly, with the help of density functional theory guided material design, (aminomethyl) piperidinium quasi-2D perovskites are selected. The lowest energy distribution and homogeneous energy landscape are achieved through carefully regulating their crystallization kinetics. We conclude that homogeneous energy landscape significantly reduces the Shockley-Read-Hall recombination and suppresses the quasi-Fermi level splitting, which is crucial to achieve high Voc.

Highlights

Reduced-dimensional perovskite materials are widely applied for perovskite photovoltaics due to their remarkable environmental stability
The device exhibits significantly improved stability compared with traditional hot-casting films due to the more ideal vertical phase alignment, which retains almost 90% of the initial power conversion efficiency (PCE) after 1000 h of storage
Short halide–halide distance affords strong antibonding interactions, which push up the valence band maximum (VBM) in principle[20]

Summary

Introduction

Reduced-dimensional (quasi-2D) perovskite materials are widely applied for perovskite photovoltaics due to their remarkable environmental stability. From the viewpoint of carrier dynamics, carrier transit time across the p-n junction is much longer than the energy transfer timescale, when considering the carrier mobility and film thickness[12] This implies that the photocarriers generating in the high bandgap species would thermally relax to the band edge of the smallest bandgap species at first, and get separated under the built-in electric field. The inhomogeneous energy landscape deteriorates the device performance by introducing extra energy loss, creating band tail states, and inhibiting minority carrier transport. Reduced low value components favorably promoted the carrier transport and effectively suppressed the charge recombination These films featuring high value phases achieved improved performance. Achieving homogeneous energy landscape in low value regions is necessary to ensure both performance and stability of the PSCs

Methods

Results

Conclusion