Ambient-air-stable inorganic Cs2SnI6double perovskite thin filmsviaaerosol-assisted chemical vapour deposition

Jack Chun-Ren Ke,David J Lewis,Alex S Walton,Paul O'Brien,Andrew G Thomas,Wendy R Flavell,Ben F Spencer

doi:10.1039/c8ta03133a

Abstract

Air-stable caesium tin iodide double perovskite (Cs2SnI6) thin films have been fabricatedviaaerosol-assisted chemical vapour deposition (AACVD).

Highlights

In recent years, perovskite solar cells (PSCs) have attracted tremendous attention,[1,2,3,4,5,6,7,8] since the rst description by Kojima et al in 2009.9 Within a decade, this type of photovoltaic technology has undergone unprecedented advances in certi cated power conversion efficiency (PCE), which has reached more than 20%.4–7 As a result, the PSCs are considered to be highly promising candidates for reduction in the cost per watt of commercial solar-energy-conversion devices
The aerosol-assisted chemical vapour deposition (AACVD)-grown Cs2SnI6 films retain high phase purity for at least $100 days aging in air with negligible CsI impurities detected over this time, as determined by X-ray diffraction
The Cs2SnI6 double perovskite which is ambipolar exhibits excellent carrier mobility when doped as an n-type semiconducting material

Summary

Introduction

Among lead-free halide perovskite materials, tin-based perovskites are widely investigated as tin is a group IV metal and can be isoelectronic with lead. The Cs2SnI6 double perovskite which is ambipolar (i.e. it can be doped as n-type or p-type) exhibits excellent carrier mobility when doped as an n-type semiconducting material It has a relatively low optimised energy band gap (Eg) of ca. 1.3 eV and high absorption coefficient (of over 105 cmÀ1 for energies above 1.7 eV), which shows great potential for use as a light absorber in photovoltaic devices.[22,23,24] Very recently, using a special architecture, Cs2SnI6-based solar cells with PCEs of ca. By combining XPS data from a number of experiments, we show that surface passivation through a layer containing excess Sn and I is one factor imparting stability of the Cs2SnI6 lms These insights will help the future development to Pb-free halide perovskites for use in photovoltaic devices

Sample preparation

Instrumentation

Results and discussion

Conclusions