Joule
Volume 3, Issue 6, 19 June 2019, Pages 1464-1477
Journal home page for Joule

Article
Caffeine Improves the Performance and Thermal Stability of Perovskite Solar Cells

https://doi.org/10.1016/j.joule.2019.04.005Get rights and content
Under an Elsevier user license
open archive

Highlights

  • Caffeine enhances both thermal stability and efficiency

  • The stabilized power conversion efficiency of 19.8% was realized

  • Thermally stable solar cells at 85°C for over 1,300 h were achieved

Context & Scale

To overcome the barrier of the commercialization of metal halide perovskite solar cells, a simple, cost-effective, and generalized strategy that mitigates the intrinsic thermal instability is strongly needed. Here, caffeine is introduced to simultaneously enhance the efficiency and thermal stability of the solar cells based on various kinds of perovskite materials. The strong interaction between caffeine and Pb2+ ions serves as a “molecular lock” that increases the activation energy during film crystallization, delivering a perovskite film with preferred orientation, improved electronic properties, reduced ion migration, and greatly enhanced thermal stability. Ultimately, a champion-stabilized efficiency of 19.8% with 1,300 h thermal stability at 85°C in nitrogen was achieved.

Summary

To increase the commercial prospects of metal halide perovskite solar cells, there is a need for simple, cost-effective, and generalized approaches that mitigate their intrinsic thermal instability. Here we show that 1,3,7-trimethylxanthine, a commodity chemical with two conjugated carboxyl groups better known by its common name caffeine, improves the performance and thermal stability of perovskite solar cells based on both MAPbI3 and CsFAMAPbI3 active layers. The strong interaction between caffeine and Pb2+ ions serves as a “molecular lock” that increases the activation energy during film crystallization, delivering a perovskite film with preferred orientation, improved electronic properties, reduced ion migration, and greatly enhanced thermal stability. Planar n-i-p solar cells based on caffeine-incorporated pure MAPbI3 perovskites, which are notoriously unstable, exhibit a champion-stabilized efficiency of 19.8% and retain over 85% of their efficiency under continuous annealing at 85°C in nitrogen.

Keywords

perovskite solar cells
thermal stability
Lewis base additive
molecular lock
caffeine

Cited by (0)

5

These authors contributed equally

6

Present address: College of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA

7

Lead Contact