Promises and challenges of perovskite solar cells

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Science  10 Nov 2017:
Vol. 358, Issue 6364, pp. 739-744
DOI: 10.1126/science.aam6323
  • Fig. 1 Commonly used PSC architectures and their state-of-the-art performance.

    (A and B) Schematics of perovskite solar cells based on a mesoporous layer (A) and planar n-i-p (B), with a conducting glass/electron contact/perovskite configuration. (C) The p-i-n configuration with a planar junction in a conducting glass/hole contact/perovskite stack, also commonly referred to as “inverted.” (D) Multijunction perovskite tandem where two or more band gap–matched absorbers are stacked to increase overall PCE. (E) Photovoltaic parameters of PSCs as calculated from the Shockley-Queisser model (bars) and metrics of selected publications (circles) with efficiencies above 20% since 2015 and in chronological order to 2017 (1725). The calculated fill factor has two maxima: (i) the maximum for the measured VOC (bars) assuming Shockley-Read-Hall recombination, and (ii) the maximum under the assumption that the theoretical VOC is achieved (dotted line). See supplementary materials for details of the calculations. Configurations: M, mesoporous; N, planar n-i-p; P, planar p-i-n; T, perovskite tandem. The perovskite composition for each report is marked in the top panel, where “mix” refers to a combination of lead-based FA, MA, I, and Br ions. Inorganic cations Rb and Cs are used in some recipes; MAPI, methylammonium lead triiodide.

  • Fig. 2 Device photophysics of state-of-the-art PSCs.

    (A) Light-harvesting efficiency (absorptance), external and internal quantum efficiency (EQE and IQE), and absorption coefficient of a mixed ion-based PSC (14). (B) Current-voltage hysteresis under 1-sun illumination (37). (C) Calculation of the maximum VOC as a function of nonradiative lifetime for a perovskite layer 500 nm thick, compared with values achieved by Bi et al. (18), Jacobsson et al. (48), Saliba et al. (21), and deQuilettes et al. (40). See supplementary materials for details of the calculations. (D and E) Shockley-Queisser efficiency (D) and calculated maximum VOC (radiative limit) (E) for a select number of PSCs by Jacobsson et al. (48), Zhao et al. (58), Eperon et al. (10), Liao et al. (81), and Noel et al. (82), compared with different established solar cells.

  • Fig. 3 The role of cations in the reproducibility of highly efficient perovskite solar cells.

    (A) Comparison of PCE values, with box plots shown alongside the corresponding data points, between 40 MAFA double-cation and 98 CsMAFA triple-cation perovskite devices. The standard deviation, a metric for reproducibility, improved from 16.37 ± 1.49% for MAFA to 19.20 ± 0.91% for CsMAFA. Twenty independent devices showed efficiencies larger than 20% (61). (B) Tolerance factor of APbI3 perovskite with A cations that are too small (Na, K, Rb), established (Cs, MA, FA), or too large [imidazolium (IA), ethylamine (EA), guanidinium (GA)]. The inset images depict the cation structures. Empirically, perovskites with a tolerance factor between 0.8 and 1.0 (dotted lines) show a photoactive black phase (solid circles) as opposed to nonphotoactive phases (open circles). Rb is very close to this limit, making it a candidate for modification of the perovskite lattice via a multication approach (21).

  • Fig. 4 Long-term stability of perovskite solar cells.

    (A) Gold migration through spiro-OMeTAD under light, MPPT, nitrogen flow at 75°C. [Adapted from (69) with permission] (B) The use of multiple cations and a PTAA hole contact shows losses of ~5% in 500 hours of MPPT in nitrogen at 85°C (21). (C) Photostability test under AM 1.5G illumination, including UV radiation for encapsulated devices based on different metal oxides (23). (D) Unencapsulated Si-perovskite tandems show remarkable MPPT stability, with a slight increase in performance and an almost unchanged performance at the end of the >1000-hour test (26). (E) MPPT of devices showing reversible losses before going through permanent degradation (78). (F and G) Room-temperature test with light soaking of planar p-i-n for 150 hours (24) (F) and light soaking of n-i-p for 500 hours (22) (G); the devices exhibit small losses under MPPT. Configurations: M, mesoporous; N, planar n-i-p; P, planar p-i-n; Si-T, Si-perovskite tandem. The layer compositions of the device stacks are summarized at the top of each graph. Each graph includes a summary of the aging conditions used.

Supplementary Materials

  • Promises and challenges of perovskite solar cells

    Juan-Pablo Correa-Baena, Michael Saliba, Tonio Buonassisi, Michael Grätzel, Antonio Abate, Wolfgang Tress, Anders Hagfeldt

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