Effects of 5-Ammonium Valeric Acid Iodide as Additive on Methyl Ammonium Lead Iodide Perovskite Solar Cells.

Daming Zheng,Yaoguang Rong,Tao Zhu,Thierry Pauporté,Changheng Tong

doi:10.3390/nano10122512

Abstract

During the past decade, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has risen rapidly, and it now approaches the record for single crystal silicon solar cells. However, these devices still suffer from a problem of stability. To improve PSC stability, two approaches have been notably developed: the use of additives and/or post-treatments that can strengthen perovskite structures and the use of a nontypical architecture where three mesoporous layers, including a porous carbon backcontact without hole transporting layer, are employed. This paper focuses on 5-ammonium valeric acid iodide (5-AVAI or AVA) as an additive in methylammonium lead iodide (MAPI). By combining scanning electron microscopy (SEM), X-ray diffraction (XRD), time-resolved photoluminescence (TRPL), current–voltage measurements, ideality factor determination, and in-depth electrical impedance spectroscopy (EIS) investigations on various layers stacks structures, we discriminated the effects of a mesoscopic scaffold and an AVA additive. The AVA additive was found to decrease the bulk defects in perovskite (PVK) and boost the PVK resistance to moisture. The triple mesoporous structure was detrimental for the defects, but it improved the stability against humidity. On standard architecture, the PCE is 16.9% with the AVA additive instead of 18.1% for the control. A high stability of TiO2/ZrO2/carbon/perovskite cells was found due to both AVA and the protection by the all-inorganic scaffold. These cells achieved a PCE of 14.4% in the present work.

Highlights

In summary, we investigated the effect of an AVA additive and of the cell structure on perovskite solar cells (PSCs)
Using a 3mp scaffold leads to a significant improvement of the PVK structural quality as shown by time-resolved photoluminescence (TRPL) and solves the potential problems of pinhole and related electrical shunt pathways
Our electrical impedance spectroscopy (EIS) study stated that the R2 element varies with the Voc, like a recombination resistance from which we extracted an ideality factor comparable to the ones determined from the Voc

Summary

Introduction

Organic–inorganic halide perovskites (PVKs) have risen as one of the most promising semiconductor families for various advanced applications in optoelectronics, such as light emitting diodes (LEDs) [1], lasers [1], photodetectors [2], scintillators [3], and solar cells [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43]. Mei et al were the first to develop these triple-mesocopic solar cells [22] In their pioneering work, they observed that 5-ammonium valeric acid iodide (HOOC(CH2)4NH3I, noted as 5-AVAI or AVA) was an important additive for getting a good pore filling and a more complete contact of PVK with the mesoporous TiO2 scaffold. They observed that 5-ammonium valeric acid iodide (HOOC(CH2)4NH3I, noted as 5-AVAI or AVA) was an important additive for getting a good pore filling and a more complete contact of PVK with the mesoporous TiO2 scaffold They stressed that the carbon top electrode presents hydrophobic properties and acts as a barrier against moisture. These PSCs successfully passed the main items of IEC61215:2016 PV qualification tests, including the damp heat test, thermal cycling test, and ultraviolet preconditioning test, and they exhibited over a 9000-h operational stability [29]

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