Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 10, Issue 41, Pages 35194-35205Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.8b12018
Keywords
defect-ordered hybrid halide perovskite solar cells; (CH3NH3)(3)Sb2I9; heterovalent metal substitution; tin(IV)-substituted (CH3NH3)(3)Sb2I9; band gap lowering
Funding
- JC Bose National Fellowship of SERB [SB/S2/JCB-001/2016]
- DST INSPIRE Fellowship [IF 140158]
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The prevailing issue of wide optical gap in defect-ordered hybrid iodide perovskites has been addressed in this effort by heterovalent substitution at the metal site. With the introduction of Sn4+ in the (CH3NH3)(3)Sb2I9 structure, we have successfully lowered the pristine optical gap (2 eV) of the perovskite to a close-to optimum one (1.55 eV). Upon such heterovalent substitution, a gradual shift in the type of electronic conduction of the perovskites was observed. As evidenced from scanning tunneling spectroscopy and correspondingly density-of-state spectra, a significant shift of Fermi energy toward the conduction band edge occurred with an increase in the tin content in the host perovskite. This shift has 10 resulted in tuning of the type of electronic conductivity from p-type to n-type and more importantly led to a better band alignment with the selective contacts of p-i-n heterojunctions. However, tin inclusion affected the surface roughness of the perovskite film in an adverse manner. Hence, the tin content was optimized by considering both the factors, namely, the band gap of the material and the surface roughness of thin films. In an energy-level-optimized planar heterojunction device, a power conversion efficiency of 2.69%.
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